CN109770930B - Method and device for determining coronary artery microcirculation resistance - Google Patents

Abstract

The invention discloses a method for determining the microcirculation resistance of coronary arteries, which comprises the steps of establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch according to a three-dimensional image model of the coronary arteries; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line; determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line; and determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch. The invention also discloses a device for determining the microcirculation resistance of coronary arteries and a storage medium.

Description

Method and device for determining coronary artery microcirculation resistance

Technical Field

The invention relates to a coronary artery angiography data processing technology, in particular to a method and a device for determining coronary artery microcirculation resistance.

Background

Fractional Flow Reserve (FFR) of coronary arteries is an evaluation criterion for the assessment of ischemic coronary heart disease. FFR is defined as the ratio of the maximum blood flow achieved by a blood vessel in the presence of a stenotic lesion to the maximum blood flow achieved by a blood vessel in the normal state, at maximum hyperemia. According to the fluid mechanics formula, the blood flow of the myocardial tissue is proportional to the perfusion pressure, so the FFR can be calculated by the ratio of the pressure at the far downstream end of the stenosis to the pressure at the upstream end of the stenosis. FFR requires interventional measurements using pressure guide wires, is expensive and complicated to operate, requires injection of adenosine to fully dilate the coronary microcirculation, is often associated with many adverse reactions, and causes physical discomfort. The coronary FFRCT technique based on hemodynamic simulation is a useful exploration of a non-invasive assessment method of FFR.

The coronary artery FFRCT technology is to reconstruct a three-dimensional geometric model of a coronary artery based on a patient coronary artery Angiography (CTA) image, construct a real and personalized physiological Flow boundary condition, perform hemodynamic simulation of the coronary artery by using a numerical simulation method, and obtain FFR (non-invasive coronary artery blood Flow Reserve fraction) of the coronary artery based on a pressure ratio of a distal end and a proximal end of a stenotic lesion obtained by calculation. On the premise that a three-dimensional (3D) reconstructed model is close to a real coronary artery, the accuracy of the calculation result of the FFRCT technology depends on the setting of hydrodynamic boundary conditions to a great extent, in the existing adopted boundary conditions, the most adopted boundary conditions are based on pressure-resistance, namely, the brachial artery blood pressure of a patient is taken as the boundary condition of the inlet pressure of the coronary artery, the outlet adopts the boundary condition of resistance, and the determination of the resistance of each outlet of the coronary artery is related to the accuracy of the calculation result of the FFRCT technology.

Therefore, how to obtain the accurate resistance of each blood outlet of the coronary artery branch so as to improve the accuracy of the calculation result of the FFRCT technology is an urgent problem to be solved.

In the invention

In view of this, the embodiments of the present invention are intended to provide a method and an apparatus for determining coronary artery microcirculation resistance, which can obtain accurate resistance of each blood outlet of a coronary artery branch, thereby improving accuracy of calculation results of the FFRCT technique.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the embodiment of the invention provides a method for determining coronary artery microcirculation resistance, which comprises the following steps:

according to the three-dimensional image model of the coronary artery, establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line;

and determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch.

In the foregoing solution, the determining the hierarchical relationship of each coronary artery branch according to the connection relationship of each centerline includes:

determining the hierarchical relationship of coronary artery branches according to the cross-connection relationship of discrete points of each coronary artery branch central line and the preset blood flow direction;

the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch;

the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch.

In the foregoing solution, the determining the blood flow volume of each coronary artery branch by using a preset allocation rule includes:

the total coronary blood volume was calculated using the following expression:

Q_cor＝Q₀M_myo ^0.75

wherein Q is_corRepresenting total coronary blood flow; q₀Denotes a predetermined coefficient, M_myoRepresenting left ventricular myocardial mass;

determining respective blood flow volumes of the left coronary artery and the right coronary artery according to preset distribution ratios of the blood flow volumes of the left coronary artery and the right coronary artery in total blood flow volumes of the coronary arteries;

the blood flow of each coronary branch is expressed in terms of:

wherein d is_mnRepresenting the diameters, Q, of the sub-coronary branches belonging to the same parent coronary branch at the root node position of the discrete point of the respective corresponding centerline_mRepresenting the total blood flow of the parent coronary branch.

In the above aspect, the determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow volume of each coronary artery branch includes:

subtracting the difference between the epicardial coronary artery pressure drop and the central venous pressure from the average aortic pressure to obtain the pressure difference from the branch end of the coronary artery to the vein end;

and dividing the quotient of the pressure difference from the end of the coronary artery branch to the end of the vein by the blood flow of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet.

In the above scheme, the method further comprises:

performing linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a first diameter fitting curve;

and when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule.

In the above scheme, the method further comprises:

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value;

performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve;

and when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule.

In the above scheme, the performing linear fitting on the coronary artery branch diameter corresponding to each discrete point by using a preset fitting rule includes:

linearly fitting the diameters of the coronary artery branches corresponding to each discrete point, and expressing a curve obtained by fitting by using the following expression:

Diameter_polyfit＝p(1)·Distance_emd+p(2)

wherein, Distance_emdRepresenting the bit order sequence of each discrete point on the centerline, p (1) representing the slope of the fitting function, p (2) representing the intercept of the fitting function, Diameter_emdThe sequence of coronary branch diameters corresponding to each discrete point is represented.

In the above scheme, the repairing the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root of the central line according to a preset repairing rule includes:

determining the diameters of the coronary artery branches corresponding to the discrete points at the root intersection positions of the central lines by adopting the following expression:

d₁＝d_n+(n-1)γ

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe diameter of the coronary artery branch corresponding to the last discrete point at the tail end of the central line is represented, n represents the bit number of the discrete point, and gamma represents the diameter difference of the coronary artery branch of the preset adjacent discrete points.

In the foregoing solution, before the fitting the first diameter fitting curve, the method further includes:

and according to a preset rejection rule, rejecting discrete points with preset length of coronary artery branches.

In the above solution, before the linear fitting is performed on the coronary branch diameter corresponding to each discrete point on the central line of the coronary branch, the method further includes:

performing Empirical Mode Decomposition (EMD) on the branch diameter of the coronary artery with the length larger than the preset branch length;

and when the EMD result is larger than the preset mode, removing the mode with the maximum fluctuation, adding the residual mode data, and determining the residual mode data as the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch.

The embodiment of the invention also provides a device for determining the microcirculation resistance of coronary arteries, which comprises: a model processing module, a first determining module, and a second determining module, wherein,

the model processing module is used for establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch according to the three-dimensional image model of the coronary artery; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

the first determining module is used for determining the blood flow of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relationship of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line;

and the second determination module is used for determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch.

In the foregoing solution, the model processing module is specifically configured to:

determining the hierarchical relationship of coronary artery branches according to the cross-connection relationship of discrete points of each coronary artery branch central line and the preset blood flow direction;

the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch;

the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch.

In the foregoing solution, the first determining module is specifically configured to:

the total coronary blood volume was calculated using the following expression:

Q_cor＝Q₀M_myo ^0.75

wherein Q is_corRepresenting total coronary blood flow; q₀Denotes a predetermined coefficient, M_myoRepresenting left ventricular myocardial mass;

determining respective blood flow volumes of the left coronary artery and the right coronary artery according to preset distribution ratios of the blood flow volumes of the left coronary artery and the right coronary artery in total blood flow volumes of the coronary arteries;

the blood flow of each coronary branch is expressed in terms of:

wherein d is_mnRepresenting the diameters, Q, of the sub-coronary branches belonging to the same parent coronary branch at the root node position of the discrete point of the respective corresponding centerline_mRepresenting the total blood flow of the parent coronary branch.

In the foregoing solution, the second determining module is specifically configured to:

subtracting the difference between the epicardial coronary artery pressure drop and the central venous pressure from the average aortic pressure to obtain the pressure difference from the branch end of the coronary artery to the vein end;

and dividing the quotient of the pressure difference from the end of the coronary artery branch to the end of the vein by the blood flow of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet.

In the above scheme, the apparatus further comprises a correction module; the correction module is used for:

performing linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a first diameter fitting curve;

and when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule.

In the foregoing solution, the modification module is further configured to:

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value;

performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve;

and when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule.

In the foregoing solution, the modification module is specifically configured to:

linearly fitting the diameters of the coronary artery branches corresponding to each discrete point, and expressing a curve obtained by fitting by using the following expression:

Diameter_polyfit＝p(1)·Distance_emd+p(2)

wherein, Distance_emdRepresenting the bit order sequence of each discrete point on the centerline, p (1) representing the slope of the fitting function, p (2) representing the intercept of the fitting function, Diameter_emdThe sequence of coronary branch diameters corresponding to each discrete point is represented.

In the foregoing solution, the modification module is specifically configured to:

determining the diameters of the coronary artery branches corresponding to the discrete points at the root intersection positions of the central lines by adopting the following expression:

d₁＝d_n+(n-1)γ

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe diameter of the coronary artery branch corresponding to the last discrete point at the tail end of the central line is represented, n represents the bit number of the discrete point, and gamma represents the diameter difference of the coronary artery branch of the preset adjacent discrete points.

In the foregoing solution, the modification module is further configured to:

and according to a preset rejection rule, rejecting discrete points with preset length of coronary artery branches.

In the foregoing solution, the modification module is further configured to:

performing EMD on the branch diameter of the coronary artery with the length larger than the preset branch length;

and when the EMD result is larger than the preset mode, removing the mode with the maximum fluctuation, adding the residual mode data, and determining the residual mode data as the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch.

Embodiments of the present invention further provide a storage medium, on which an executable program is stored, and the executable program, when executed by a processor, implements the steps of the method for determining coronary artery microcirculation resistance according to any of the above methods.

The embodiment of the invention also provides a device for determining coronary artery microcirculation resistance, which comprises a processor, a memory and an executable program which is stored on the memory and can be run by the processor, wherein when the processor runs the executable program, the step of any method for determining coronary artery microcirculation resistance is executed.

According to the method and the device for determining the microcirculation resistance of the coronary arteries, which are provided by the embodiment of the invention, a central line which is formed by discrete points and respectively corresponds to each coronary artery branch is established according to a three-dimensional image model of the coronary arteries; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line; determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line; and determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch. Therefore, the flow of each branch of the coronary artery is accurately calculated according to the diameter of the root of the branch at the bifurcation of the coronary artery by a step-by-step distribution method, the accurate resistance of each blood outlet of each branch of the coronary artery is obtained, and the accuracy of the calculation result of the FFRCT technology is improved.

Drawings

FIG. 1 is a schematic flow chart of a method for determining coronary arterial microcirculation resistance according to an embodiment of the present invention;

FIG. 2 is a schematic representation of raw CTA data in accordance with an embodiment of the present invention;

FIG. 3 is a schematic representation of a three-dimensional geometric model reconstructed from CTA data in accordance with an embodiment of the present invention;

FIG. 4 is a schematic diagram of a three-dimensional geometric model of aorta and coronary artery and a coronary lattice cloud according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of discrete points on the centerline of a coronary artery branch according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of the distribution of parent nodes and child nodes at a bifurcation site according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a coronary artery branch naming according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of a coronary artery branch diameter fit according to an embodiment of the present invention;

FIG. 9 is a schematic representation of the naming and resistance of a real coronary artery branch according to an embodiment of the present invention;

FIG. 10 is a diagram illustrating the FFR calculation result of the left branch of the real coronary artery according to the embodiment of the present invention;

FIG. 11 is a schematic representation of the naming and resistance of a real coronary branch after diameter repair in accordance with an embodiment of the present invention;

FIG. 12 is a schematic diagram illustrating the FFR calculation results of the left and right branches of the real coronary artery after diameter repair according to an embodiment of the present invention;

fig. 13 is a schematic structural diagram of a device for determining coronary artery microcirculation resistance according to an embodiment of the present invention.

Detailed Description

In the embodiment of the invention, a central line which is respectively corresponding to each coronary artery branch and is formed by discrete points is established according to a three-dimensional image model of the coronary artery; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line; determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line; and determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch.

The method for determining the resistance of the microcirculation of the coronary arteries, which is provided by the embodiment of the invention, as shown in fig. 1, comprises the following steps:

step 101: according to the three-dimensional image model of the coronary artery, establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

here, coronary artery image data can be acquired through CTA and other methods, a three-dimensional image model of a coronary artery is established through setting a threshold, selecting a certain number of isosurface, establishing a connected domain and the like, and a coronary artery lattice cloud is extracted. The coronary artery branch may refer to the whole vessel branch of the whole coronary artery, such as the left coronary artery, the right coronary artery, the main coronary artery and the bifurcation coronary artery of the left and right coronary arteries;

specifically, CTA image data is shown in fig. 2. The CTA image data can be imported into three-dimensional reconstruction software, with the lighter regions representing essentially the aorta, the lumen of the major coronary arteries, and the darker regions representing the myocardium and other tissue of the patient's heart; setting an image parameter threshold, selecting a certain number of isosurfaces, establishing a connected domain, reconstructing to generate a three-dimensional image model formed by triangular meshes, and performing surface smoothing according to a Laplace algorithm to finally obtain the three-dimensional geometric model containing the heart, the aorta and the coronary artery as shown in FIG. 3. In order to better obtain a coronary artery three-dimensional model, methods such as interpolation, smoothing and the like can be adopted to process calcified plaque of coronary artery and carry out smoothing and hole filling;

setting parameter thresholds such as image brightness and contrast, identifying, separating a coronary artery model comprising a plurality of main coronary arteries such as a Left Anterior Descending (LAD) artery, a left branch (LCX) artery, a Right Coronary (RCA) artery and branches thereof from the segmented aorta and the coronary arteries shown in the three-dimensional geometric model comprising the heart, the aorta and the coronary arteries in FIG. 4a, and extracting a lattice cloud model of the coronary artery model shown in FIG. 4b, wherein the lattice cloud is a discretization form of the coronary artery model;

after the coronary artery lattice cloud model is obtained, a central line which is formed by discrete points and corresponds to each coronary artery branch can be extracted, and the hierarchical relation of each coronary artery branch can be determined according to the connection relation of each central line, such as the tree structure of the central line; the central line can be formed by connecting discrete points, the interval of the discrete points can be preset, and the spatial distance of the interval can be determined by combining the spatial linear distance, the spatial angle and the like. For example, the discrete point space linear distance interval may be set to 0.25mm to 0.75mm, such as 0.5 mm. The centerline of the coronary artery branch is commonly referred to as the coronary artery branch keel and the discrete points making up the centerline may be commonly referred to as the coronary artery branch keel nodes.

Furthermore, the coronary artery branch hierarchical relationship can be determined according to the cross connection relationship of discrete points of the central line of each coronary artery branch and the preset blood flowing direction; the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch; the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch;

here, the parent coronary artery branch and the child coronary artery branch may have a plurality of levels, the parent coronary artery branch may be a child coronary artery branch of an upper level, and the child coronary artery branch may be a parent coronary artery branch of a lower level; the hierarchical relationship of coronary artery branches may be determined according to a blood flow direction, including a parent coronary artery branch and a child coronary artery branch, typically the child coronary artery branch is connected with the parent coronary artery branch by a crossing point, and the blood flow direction is from the parent coronary artery branch to the child coronary artery branch.

In practical application, as shown in fig. 4a and 4b, a coronary artery lattice cloud can be extracted, the lattice cloud is converted into a binary high-dimensional matrix, a connected domain is calculated, a smaller connected domain is removed, a skeleton is extracted by using a coronary artery skeleton extraction algorithm, and a keel node index is established. The keel nodes are discrete points of the central line. The keel node index is the relationship between a child node and a father node;

specifically, firstly, converting a dot matrix cloud into a binary high-dimensional matrix, calculating a connected domain, and rejecting a smaller connected domain, wherein the connected domain with less than 100 pixel points is generally rejected;

secondly, extracting bones by using a coronary artery bone extraction algorithm, marking the physical coordinate positions of keel nodes, and recording the positions in the first three columns in a matrix A, wherein the total number of the keel nodes is N, and the spatial position of the ith node is p_i＝(x_i,y_i,z_i) And (4) showing. Calculating the equivalent area A of coronary artery on each node_iEquivalent diameter d_iDirection of blood flow v_i(first derivative of spatial position) and the like. Equivalent area refers to the area enclosed by a perpendicular section to the coronary arteries; the equivalent diameter is calculated by the formula

Calculating the blood flow direction according to respective mathematical definition, adding all data into the matrix A according to the keel coordinate position, and directly calling the subsequent calculation;

finally, find node i in the reverse direction of blood flow-v_iThe current node is called a child node, which indicates that the blood flow direction is from the parent node to the child node, and the node is a discrete point forming the centerline of the coronary artery branch. It should be noted that: the blood flow entry point has no parent node, the blood flow exit point has no child node, and the bifurcation point is a parent node of the plurality of child nodes. And searching a branch path from the inlet to the outlet according to the spatial relationship between the child node and the parent node, namely searching the parent node of each node from the outlet until the inlet node of the coronary artery. The coronary artery keel nodes traverse sequentially from the entrance to the first-level branch, the second-level branch and the like until all the exits, so that the program searches all the exits from the coronary artery entrance to obtain a coronary artery branch hierarchical relation graph shown in fig. 5, namely keel indexes. The outlet of the coronary artery can be preset, for example, the position of the tail end of a coronary artery branch with the diameter of 1-2 mm is set as the outlet of the coronary artery; wherein the bifurcation is the intersection of the coronary branches.

In practical application, the spatial position relationship of the coronary artery branches can be established according to the arrangement of the coronary artery branches and the preset sequence, and the coronary artery branches are named according to the preset naming rule; thus, the coronary artery branches are mathematically and geometrically graded and named from top to bottom and from left to right, and the problem that the flow at the tail end of the coronary artery cannot be regularly and programmatically evaluated before FFRCT calculation is solved;

specifically, according to the above-mentioned coronary artery keel node index relationship, a coronary artery branch bifurcation point is found, and the sequence of traversing the sub-nodes of the coronary artery branch bifurcation point along the coronary artery from top to bottom and from left to right along the heart center is determined;

based on the keel data matrix A, starting from the coronary artery entrance keel node, i.e. from the discrete intersection of the aorta with the coronary arteriesAnd starting points, traversing keel nodes to a first bifurcation point according to the index relation of the keel nodes of the coronary artery, acquiring and recording the sequence of sub-nodes of the first bifurcation point, and storing the sequence in a matrix B. Taking the first bifurcation point containing two child nodes as an example, according to the relationship that the child nodes of the bifurcation point all share one father node, the direction vector Dir _ fast pointing to the father node of the bifurcation point and the direction vector Dir _ son pointing to two first-level child nodes B (1) and B (2) of the bifurcation point are calculated₁，Dir_son₂Since the distance between the keel node and the point is about one pixel (the distance between two pixel points is about 0.3mm), the three vectors can be regarded as being in the same plane. According to the right-hand rule, normal vectors of direction vectors of a bifurcation point pointing to a parent node of the bifurcation point and direction vectors of bifurcation points pointing to two first-level child nodes are respectively calculated and can be respectively expressed by expressions (1) and (2):

Normal₁＝cross(dir_father,Dir_son₁) (1)

Normal₂＝cross(dir_father,Dir_son₂) (2)

positioning the heart Center according to the distribution of the left and right coronary arteries, calculating a direction vector Dir _ Center of a bifurcation point pointing to the sphere Center by taking the coronary artery Center as the sphere Center, and judging the storage positions of the two sub-nodes in the matrix B by calculating dot products a and B of the normal vector and the direction vector of the bifurcation point pointing to the sphere Center; a and b can be expressed by expressions (3) and (4), respectively:

a＝Dir_Center·Noraml₁ (3)

b＝Dir_Center·Noraml₂ (4)

when a is less than 0 and less than B, the positions of elements in the matrix B are kept unchanged, and as shown in FIG. 6a, two keel nodes are distributed in a left-right mode;

when B is less than 0 and less than a, the positions of elements in the matrix B are interchanged, and as shown in figure 6a, the two keel nodes are in a left distribution type;

when a is greater than 0 and b is greater than 0, calculating the Dir _ fast and Dir _ son₁And Dir _ son₂The included angles are expressed by expressions (5) and (6), respectively:

θ₁＝acos(dot(Dir_father·Dir_son₁)/(norm(Dir_father)·norm(Dir_son₁))) (5)

θ₂＝acos(dot(Dir_father·Dir_son₂)/(norm(Dir_father)·norm(Dir_son₂))) (6)

if theta is greater than theta₁＞θ₂The positions of the elements in the matrix B remain unchanged; instead, interchanging the element positions in matrix B, as shown in fig. 6B, the two coronary branches are left-distributed;

when a is less than 0 and b is less than 0, the vector Dir _ fast and the vector Dir _ son are calculated₁And Dir _ son₂Included angle theta₁,θ₂: if theta is greater than theta₁＞θ₂Interchanging the element positions in the matrix B; in contrast, the positions of the elements in the matrix B remain unchanged, as shown in fig. 6c, and the two keel nodes are in a right distribution type;

according to the rule, after the positions of the elements in the matrix B are changed, all the remaining bifurcation points are sequentially traversed until all the outlets of the coronary artery are traversed, so that the traversing sequence of the coronary artery branches from top to bottom and from left to right is determined.

Further, the coronary artery branches may be named based on their spatial position order;

the coronary artery trunk is named C according to the traversal order specified for the coronary artery branches above_mThe other branches of the coronary artery are named according to the determined left and right branches of the coronary artery in the order of 0(m is 0), and the left and right branches under one branch are named according to a certain rule, and can be expressed by expression (7):

C_mn＝C_m×10+n (7)

where m is the naming attribute of the last branch, n-1 denotes the left branch, n-2 denotes the right branch, and all keels that thus circulate to all coronary branches are named, as shown in fig. 7;

first, the coronary artery entrance keel node is named as attribute C₀When the number of the keel nodes is 0, sequentially traversing all the rest keel nodes of the main trunk, and sequentially inheriting the naming attribute of the father node of each keel node;

secondly, when the keel traverses from the main trunk to the first bifurcation point, the left branch L of the first bifurcation point is appointed according to the determined traversal sequence of the coronary artery branches from top to bottom and from left to right₀₁The first keel node grade is C₀₁＝C₀X 10+1 ═ 1, right branch R₀₂The first keel joint is named as C₀₂＝C₀X 10+2 ═ 2. All the rest keel nodes of the branch inherit the name attribute of the father node of the branch in sequence;

finally, when branch L is traversed subsequently₀₁When a bifurcation point is encountered, according to the traversal sequence of the bifurcation point of the coronary artery branches based on the left to the right of the heart, a left branch under the bifurcation point is designated as C₀₁₁＝C₀₁X 10+1 ═ 11, right branch rating C₀₁₂＝C₀₁X 10+2 ═ 12; likewise, branch R₀₂Branches after the rear bifurcation point are all according to branch L₀₁The cases are named, namely C₀₂₁＝C₀₂×10+1＝21，C₀₂₂＝C₀₂X 10+2 ═ 22, this loop continues until the entire coronary keel node is traversed, completing the named coronary branch as shown in fig. 7.

Step 102: determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line;

here, the total blood volume of the coronary artery may be assigned to each coronary artery branch according to a preset assignment rule. The preset allocation rule can be determined according to the blood allocation relation of the parent coronary artery branch and the child coronary artery branch;

further, the myocardial mass of the left ventricle can be calculated from the myocardium of the patient obtained by organ isolation, and the blood flow of the whole coronary artery, which is the law of the abnormal growth between the coronary blood flow and the myocardial mass, can be expressed by expression (8):

Q_cor＝Q₀M_myo ^0.75 (8)

wherein Q is_corIs total coronary artery blood flow；Q₀A constant coefficient, which can be taken as 5.4; m_myoLeft ventricular myocardial mass;

the profile of the coronary artery includes: left dominant, balanced, and right dominant; determining the blood flow Q of the left coronary artery from the total blood flow of the whole coronary artery_{cor_left}Blood flow Q to the right coronary artery_{cor_right}The ratio of the two is respectively 8: 2. 7.5: 2.5 and 7: 3. for example, if the coronary artery profile is the right dominant profile, then the coronary left and right branch flow distribution is: q_{cor_left}＝70％Q_cor，Q_{cor_right}＝30％Q_cor；

In combination with poisson's law, the blood flow in a coronary artery branch is proportional to the third power of the corresponding branch diameter, and can be expressed by expression (9):

wherein Q is the intravascular flow, d is the diameter of the blood vessel, mu is the hemodynamic viscosity coefficient, and lambda is a proportionality constant representing the energy consumed by the metabolism of the blood vessel per unit volume;

determining respective blood flow volumes of a left coronary artery branch and a right coronary artery branch according to the proportion of preset left coronary artery blood flow volume and preset right coronary artery blood flow volume in total blood flow volumes of coronary arteries;

the blood flow of each coronary branch is expressed by expression (10) as:

wherein d is_mnRepresenting the diameters, Q, of the sub-coronary branches belonging to the same parent coronary branch at the root node position of the discrete point of the respective corresponding centerline_mRepresenting the total blood flow of the parent coronary artery branch, m representing the parent coronary artery branch, n representing different child coronary artery branches of the m parent coronary artery branches;

taking the bifurcation of the main coronary artery into two sub-coronary artery branches as an example, d₀Is the diameter of the main coronary artery, d₀₁And d₀₂The diameters of the coronary artery branches corresponding to the two primary sub-nodes under the first bifurcation point respectively;

calculating the total blood flow of left (right) coronary artery according to the distribution pattern of coronary artery branches, i.e. main trunk l_mBlood flow volume Q_m(m ═ 0). The flow rates of other branches of the coronary artery are distributed according to the determined left and right orders of the branches of the coronary artery, and the flow rates of the left and right branches under one branch are distributed according to a certain rule, and the flow rates of the two sub-coronary artery branches can be expressed by expression (11):

wherein, m is the naming attribute of the last branch, n-1 represents the left branch, n-2 represents the right branch, and the flow is circulated to all the coronary artery branches;

according to the classification of coronary artery branches and the distribution rule of coronary artery blood flow from top to bottom, the coronary artery branch diameters of the second nodes of the left branch and the right branch under the first bifurcation point are respectively obtained, and the branch l is obtained by calculation₀₁And l₀₂The blood flow volume of (c) can be expressed by expressions (12) and (13), respectively:

branch l₀₁Bifurcating to obtain branch l₀₁₁And l₀₁₂According to the same distribution rule, calculating to obtain branch l₀₁₁And l₀₁₂The blood flow volume of (c) can be expressed by expressions (14) and (15), respectively:

likewise, branch l₀₂Bifurcating to obtain branch l₀₂₁And l₀₂₂According to the same distribution rule, calculating to obtain branch l₀₂₁And l₀₂₂The blood flow volume of (c) can be expressed by expressions (16) and (17), respectively:

if branch l₀₁₁、l₀₁₂、l₀₂₁And l₀₂₂If there is a further bifurcation, the blood flow of the next branch is distributed step by step according to the diameter of the bifurcation according to the above coronary artery grading principle, and the circulation is continued until the bifurcation does not exist in the branch, namely the outlet of the branch is the outlet of the coronary artery branch, and the blood flow corresponding to the branch is the blood flow of the outlet of the coronary artery branch.

Further, a preset fitting rule is adopted to perform linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line to obtain a first diameter fitting curve; when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule;

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value; performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve; when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, according to a preset repair rule, performing repair treatment on the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line;

here, the discrete point at the intersection position of the centerline root is a discrete point at the intersection position of the parent coronary artery branch and the child coronary artery branch and at the intersection position of the child coronary artery branch.

Specifically, the comparison of the coronary artery branch center line extracted from the three-dimensional coronary artery point cloud, that is, the coronary artery branch keel and the original three-dimensional coronary artery point cloud, shows that the diameter obtained may be inaccurate due to the fact that the calculation difficulty is large, and the extracted equivalent diameter is smaller than the real coronary artery branch diameter due to the fact that the concentration of the contrast agent at the tail end of the outlet branch is reduced. In addition, it was found from the three-dimensional coronary artery model reconstructed from the CTA image that stenosis may occur in the coronary artery branches at the bifurcation root. If the diameter of the bifurcation is directly taken to distribute the flow of the coronary artery, a large error may be generated, which causes inaccurate calculation of the microcirculation resistance at the tail end of the coronary artery branch, and further causes inaccurate calculation of the FFR. The method can be used for repairing the stenosis condition at the crossing position by determining the position of the coronary artery branch stenosis;

therefore, preferably, before linear fitting is performed on the coronary artery branch diameter corresponding to each discrete point on the central line of the coronary artery branch, the correction module 134 may reject discrete points of the coronary artery branch with the preset length according to a preset rejection rule; the preset elimination rule can be set according to the actual condition of the coronary artery model, and the intersection points and/or the tail ends of the coronary artery branches are eliminated; the preset length can be set according to the abnormal condition of the coronary artery branch, such as 1mm or 2 mm;

specifically, abnormal points at the head and the tail of the coronary artery branch are removed. Comparing the keel nodes at the bifurcation with the bifurcation areas of the real coronary branches, the finding that the main trunk of the coronary branch has about 1mm keel nodes, and the bifurcation branches have about 2mm keel nodes in the bifurcation triangular areas is that the real coronary branch bifurcations are connected with the main trunk of the coronary branch. To coronary artery branch trunk, reject the fossil fragments node in the terminal 1mm, to inside branch, the fossil fragments node in 2mm and 1mm is rejected respectively to the head and the tail, to export branch, reject equally the fossil fragments node in head and the tail 2mm and 1mm, as new branch fossil fragments node.

Further, the modification module 134 may perform EMD on the coronary artery branch diameter whose length is greater than the preset branch length, and when the EMD result is greater than the preset mode, remove the mode with the largest fluctuation, and add the remaining mode data to determine a coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch;

specifically, the equivalent diameter of the coronary branch keel node is filtered. For coronary artery with longer branches, namely coronary artery branches with length larger than the preset branch length, EMD is respectively carried out on equivalent diameters of different branch coronary artery branches by using an EMD method, different modes are generated after decomposition, for coronary artery branches with length smaller than or equal to two modes, the branch diameters are kept unchanged, and the Diameter sequence is recorded as Diameter_emd(ii) a Otherwise, removing the mode with the maximum fluctuation, and adding the residual mode data to obtain a new coronary artery branch keel Diameter sequence Diameter_emd(ii) a Wherein, 20 keel nodes are taken according to the preset branch length. For coronary artery branches with keel nodes less than or equal to 20 nodes, filtering is not carried out, and Diameter sequences are recorded_emd；

Here, the performing linear fitting on the coronary artery branch diameter corresponding to each discrete point by using the preset fitting rule includes: linearly fitting the diameters of the coronary artery branches corresponding to each discrete point, and expressing a curve obtained by fitting by using the following expression: the first and second diameter-fitted curves may be fitted using the same fitting method; the first diameter fitting curve and the second diameter fitting curve can adopt fitting expressions in the same form;

usually, it is normalThe diameter from the intersection to the end of the coronary artery branch of (1) is a decreasing series, i.e., the slope of the fitting function is less than 0; firstly, the Diameter distribution of coronary artery branches of different branches can be fitted to obtain a first Diameter fitting curve Diameter_1polyfitThe fitted functions are linear functions, and can be expressed by expression (18):

Diameter_1polyfit＝p₁(1)·Distance_emd+p₁(2) (18)

wherein, Distance_emdRepresenting the bit order, p, of each discrete point on the central line₁(1) As the slope of the fitted function, p₁(2) Representing the intercept of the fitting function, p₁(1) And p₁(2) Are each p₁＝polyfit(Distance_emd,Diameter_emd1) two constants obtained by fitting, Diameter_emdThe sequence of coronary branch diameters corresponding to each discrete point is represented. The polyfit () represents a fitting function;

when the slope p of the fitting function₁(1) When the diameter is more than 0, as shown in fig. 8, the stenosis condition of the coronary artery branches at the intersection can be preliminarily determined, and the diameter of the coronary artery branch corresponding to the discrete point at the intersection position of the root of the central line is repaired according to a preset repairing rule; the set repairing rule can be determined according to the diameter distribution of coronary artery branches, and the diameters corresponding to the discrete points at the intersection positions can be repaired by adopting the diameters of the adjacent discrete points.

Further, the coronary branch diameter corresponding to the discrete point at the intersection position of the root of the central line can be determined by using the expression (19):

d₁＝d_n+(n-1)γ (19)

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe method comprises the steps of representing the coronary artery branch diameter corresponding to the last discrete point at the tail end of the central line of the same coronary artery branch, representing the position of the last discrete point by n, and representing the coronary artery branch diameter difference of preset adjacent discrete points by gamma. When the discrete point interval is set to 0.25 mm-0.75 mm, the value range of gamma can be set to 0.0005mm-0.0015 mm, when the interval of the discrete points is 0.5mm, gamma is 0.001 mm;

when the slope p of the fitting function₁(1) When the number is less than 0, the situation that the coronary artery branches are not narrowed at the intersection can be preliminarily determined, and the repair is not needed; however, it cannot be excluded that there is a wide stenosis in the middle of the coronary branches, and that the slope p of the function is such that a stenosis occurs in the middle of the coronary branches₁(1) Less than 0 may also occur; in order to eliminate the influence of the diameter of the stenosis position on the fitting function, the first-time fitting function can be used for calculating the stenosis rate of the current coronary artery branch;

can utilize Diameter_1polyfitAnd Diameter_emdIs divided by Diameter_1polyfitAs the first diameter-fitted curve stenosis rate at the coronary artery branch stenosis, the first diameter-fitted curve stenosis rate can be expressed by expression (20):

StenosisRate₁＝(Diameter_1polyfit-Diameter_emd)/Diameter_1polyfit (20)

due to the function slope p₁(1) < 0, it is possible to preliminarily locate the position where the coronary artery branch stenosis occurs not to occur at the root of the bifurcation. For branches where no stenosis is present or where the degree of stenosis is low, the fitted keel diameter function can be considered as the diameter distribution of the ideal coronary branches, whereas for coronary branches where a severe stenosis is present in the middle, the fitted function is not very close to the diameter distribution of the real coronary branches due to the presence of stenosis. Therefore, discrete points with stenosis rate larger than a first preset stenosis rate threshold value, such as 50%, can be eliminated to obtain a new Diameter coronary artery branch Diameter sequence Diameter_newFitting the diameters of the coronary artery branches after the discrete points are removed by adopting a fitting method of fitting the same first Diameter fitting curve to obtain a second Diameter fitting curve Diameter_2polyfitCombined with Diameter_newAnd Distance_newFitting to obtain Diameter_2polyfitThe expression (21) can be used to represent:

Diamete_2polyfit＝p₂(1)·Distance_new+p₂(2) (21)

wherein p is₂(1) As the slope of the fitted function, p₂(2) Representing the intercept of the fitting function, p₂(1) And p₂(2) Are each p₂＝polyfit(Distance_new,Diameter_new1) two constants obtained by fitting, Distance_newRepresents the bit order sequence for each discrete point on the centerline, i.e., the bit order sequence for each discrete point on the centerline. The polyfit () represents a fitting function; here, expressions (18) and (21) are the same calculation method except that the variables are different.

Reuse of Diamete_2polyfitAnd Diameter_newIs divided by diameter_2polyfitThe stenosis rate of the second diameter-fitted curve, which is a coronary artery branch, can be expressed by expression (22):

StenosisRate₂＝(Diameter_2polyfit-Diameter_new)/Diameter_2polyfit (22)

here, the stenosis rate of the first diameter-fitted curve and the stenosis rate of the second diameter-fitted curve respectively represent the stenosis rates of the coronary artery branches before and after passing through the discrete point where the rejection stenosis rate is greater than the first preset stenosis rate threshold. After two fits, for the stenosis rate at the intersection position, if it is greater than a second preset stenosis rate threshold, it is determined that stenosis has occurred. According to a preset repairing rule, repairing the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root of the central line; the repairing method is consistent with the method for determining the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root part of the central line by adopting the expression (19), and the details are not repeated.

Therefore, the coronary artery branch with stenosis at the root of the coronary artery branch is repaired to obtain the new equivalent diameter of the bifurcation, and the blood flow of the coronary artery branch is directly distributed according to the repair, so that the accuracy of the flow distribution of the coronary artery branch is improved.

Furthermore, the stenosis of the coronary artery branch can be marked for the reference of the medical staff. Here, the stenosis rate maximum values corresponding to different coronary artery branches may be searched, and it is generally clinically concerned that the main coronary artery branches have a stenosis rate higher than a certain threshold, for example, 50%, and therefore, the maximum value having a stenosis rate smaller than the threshold is removed from the maximum values of the coronary artery branches, for the maximum value having a stenosis rate larger than the threshold, the maximum value coordinate is obtained and positioned on the coronary artery branch keel, the coronary artery branch keel nodes are searched forward and backward from the stenosis coordinate point, respectively, until the corresponding stenosis rate is smaller than or equal to a certain value, for example, 10%, the coronary artery branch keel node farthest from the stenosis point forward and backward is marked and recorded, and the distance of the keel nodes at both ends along the keel direction is calculated as the stenosis length StenosisLength. Stenosis information can be provided to medical personnel for reference.

Step 103, determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch;

here, the resistance of the downstream coronary branch microcirculation corresponding to different branch outlets of the normal coronary artery in the resting state is calculated by combining the relationship among the pressure, the blood flow and the vascular resistance in the resting state of the coronary artery. The preset blood outlet can be determined according to the diameter of the tail end of the coronary artery branch, the diameter of the blood outlet can be preset, the tail end of the coronary artery branch is smaller than the diameter of the preset blood outlet, and the coronary artery branch is determined to be the coronary artery branch corresponding to the preset blood outlet. The diameter of the preset blood outlet can be 1-2 mm.

Preferably, the mean aortic pressure is subtracted from the epicardial coronary pressure drop, and then the central venous pressure is subtracted to obtain the pressure difference from the end of the coronary artery branch to the end of the vein; dividing the coronary artery pressure by the quotient of the blood flow volume of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a resting state;

specifically, under the condition that an epicardial blood vessel is not narrowed, the epicardial coronary artery pressure drop of a normal person is clinically measured to be 1-2 mmHg, 1mmHg can be taken, and the coronary artery inlet pressure is taken as the mean aortic pressure P_a90mmHg, distal pressure of coronary microcirculation, i.e. central venous pressure P_d6.25mmHg, the pressure difference Δ P from the end of the coronary branch to the end of the vein is thus equal to ((P)_a-1)-P_d) 82.75 mmHg. According to Δ P ═ Q × R_rQ is the blood flow of the coronary artery branch corresponding to the preset blood outlet, and the microcirculation resistance of the tail end of each branch is ensured under the resting state

Finally, obtaining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in the hyperemia state according to the proportion coefficient of the microcirculation resistance of the coronary artery branch in the preset rest state and the microcirculation resistance of the coronary artery branch in the hyperemia state; calculating the microcirculation resistance R of the branch end of the coronary artery in a hyperemia state according to a preset proportionality coefficient such as 0.24_h＝0.24R_r. Thus, the calculation of the microcirculation resistance at the end of each branch coronary artery is completed.

Based on this method, the classification and resistance display of the real coronary branches is shown in fig. 8, and the coronary FFR distribution is obtained by CFD calculation.

Fig. 10 shows a table of FFR calculation results of the left coronary branch obtained by performing FFR calculation with respect to the naming and resistance maps of the real coronary keel points shown in fig. 9. The FFR calculation results of the left and right coronary branches obtained by performing the FFR calculation with respect to the naming and resistance maps of the real coronary keel points after the diameter of the cross-site discrete points is restored in fig. 11 are shown in fig. 12.

Therefore, the flow of each branch of the coronary artery is accurately calculated according to the diameter of the root of the branch at the bifurcation of the coronary artery by a step-by-step distribution method, the accurate resistance of each outlet of each branch of the coronary artery is obtained, and the accuracy of the calculation result of the FFRCT technology is improved.

As shown in fig. 13, the apparatus for determining coronary artery microcirculation resistance according to the embodiment of the present invention includes: a model processing module 131, a first determining module 132, and a second determining module 133, wherein,

the model processing module 131 is configured to establish a central line formed by discrete points corresponding to each coronary artery branch according to the three-dimensional image model of the coronary artery; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

here, coronary artery image data can be acquired through CTA and other methods, a three-dimensional image model of a coronary artery is established through setting a threshold, selecting a certain number of isosurface, establishing a connected domain and the like, and a coronary artery lattice cloud is extracted. The coronary artery branch may refer to the whole vessel branch of the whole coronary artery, such as the left coronary artery, the right coronary artery, the main coronary artery and the bifurcation coronary artery of the left and right coronary arteries;

specifically, CTA image data is shown in fig. 2. The CTA image data can be imported into three-dimensional reconstruction software, with the lighter regions representing essentially the aorta, the lumen of the major coronary arteries, and the darker regions representing the myocardium and other tissue of the patient's heart; setting an image parameter threshold, selecting a certain number of isosurfaces, establishing a connected domain, reconstructing to generate a three-dimensional image model formed by triangular meshes, and performing surface smoothing according to a Laplace algorithm to finally obtain the three-dimensional geometric model containing the heart, the aorta and the coronary artery as shown in FIG. 3. In order to better obtain a coronary artery three-dimensional model, methods such as interpolation, smoothing and the like can be adopted to process calcified plaque of coronary artery and carry out smoothing and hole filling;

setting parameter thresholds such as image brightness and contrast, identifying, separating a coronary artery model comprising a plurality of main coronary arteries such as LAD (coronary artery occlusion), LCX (left-handed control) artery, RCA (Rac artery occlusion) artery and branches thereof from segmented aorta and coronary arteries shown in a three-dimensional geometric model comprising the heart, the aorta and the coronary arteries in FIG. 4a, and extracting a lattice cloud model of the coronary artery model shown in FIG. 4b, wherein the lattice cloud is a discretization form of the coronary artery model;

after the coronary artery lattice cloud model is obtained, a central line which is formed by discrete points and corresponds to each coronary artery branch can be extracted, and the hierarchical relation of each coronary artery branch can be determined according to the connection relation of each central line, such as the tree structure of the central line; the central line can be formed by connecting discrete points, the interval of the discrete points can be preset, and the spatial distance of the interval can be determined by combining the spatial linear distance, the spatial angle and the like. For example, the discrete point space linear distance interval may be set to 0.25mm to 0.75mm, such as 0.5 mm. The centerline of the coronary artery branch is commonly referred to as the coronary artery branch keel and the discrete points making up the centerline may be commonly referred to as the coronary artery branch keel nodes.

Furthermore, the coronary artery branch hierarchical relationship can be determined according to the cross connection relationship of discrete points of the central line of each coronary artery branch and the preset blood flowing direction; the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch; the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch;

here, the parent coronary artery branch and the child coronary artery branch may have a plurality of levels, the parent coronary artery branch may be a child coronary artery branch of an upper level, and the child coronary artery branch may be a parent coronary artery branch of a lower level; the hierarchical relationship of coronary artery branches may be determined according to a blood flow direction, including a parent coronary artery branch and a child coronary artery branch, typically the child coronary artery branch is connected with the parent coronary artery branch by a crossing point, and the blood flow direction is from the parent coronary artery branch to the child coronary artery branch.

In practical application, as shown in fig. 4a and 4b, a coronary artery lattice cloud can be extracted, the lattice cloud is converted into a binary high-dimensional matrix, a connected domain is calculated, a smaller connected domain is removed, a skeleton is extracted by using a coronary artery skeleton extraction algorithm, and a keel node index is established. The keel nodes are discrete points of the central line. The keel node index is the relationship between a child node and a father node;

specifically, firstly, converting a dot matrix cloud into a binary high-dimensional matrix, calculating a connected domain, and rejecting a smaller connected domain, wherein the connected domain with less than 100 pixel points is generally rejected;

secondly, extracting bones by using a coronary artery bone extraction algorithm, marking the physical coordinate positions of keel nodes, and recording the positions in the first three columns in a matrix A, wherein keels are arranged in the matrix AThe total number of nodes is N, and the spatial position of the ith node is p_i＝(x_i,y_i,z_i) And (4) showing. Calculating the equivalent area A of coronary artery on each node_iEquivalent diameter d_iDirection of blood flow v_i(first derivative of spatial position) and the like. Equivalent area refers to the area enclosed by a perpendicular section to the coronary arteries; the equivalent diameter is calculated by the formula

Calculating the blood flow direction according to respective mathematical definition, adding all data into the matrix A according to the keel coordinate position, and directly calling the subsequent calculation;

finally, find node i in the reverse direction of blood flow-v_iThe current node is called a child node, which indicates that the blood flow direction is from the parent node to the child node, and the node is a discrete point forming the centerline of the coronary artery branch. It should be noted that: the blood flow entry point has no parent node, the blood flow exit point has no child node, and the bifurcation point is a parent node of the plurality of child nodes. And searching a branch path from the inlet to the outlet according to the spatial relationship between the child node and the parent node, namely searching the parent node of each node from the outlet until the inlet node of the coronary artery. The coronary artery keel nodes traverse sequentially from the entrance to the first-level branch, the second-level branch and the like until all the exits, so that the program searches all the exits from the coronary artery entrance to obtain a coronary artery branch hierarchical relation graph shown in fig. 5, namely keel indexes. The outlet of the coronary artery can be preset, for example, the position of the tail end of a coronary artery branch with the diameter of 1-2 mm is set as the outlet of the coronary artery; wherein the bifurcation is the intersection of the coronary branches.

In practical application, the spatial position relationship of the coronary artery branches can be established according to the arrangement of the coronary artery branches and the preset sequence, and the coronary artery branches are named according to the preset naming rule; thus, the coronary artery branches are mathematically and geometrically graded and named from top to bottom and from left to right, and the problem that the flow at the tail end of the coronary artery cannot be regularly and programmatically evaluated before FFRCT calculation is solved;

specifically, according to the above-mentioned coronary artery keel node index relationship, a coronary artery branch bifurcation point is found, and the sequence of traversing the sub-nodes of the coronary artery branch bifurcation point along the coronary artery from top to bottom and from left to right along the heart center is determined;

based on the keel data matrix A, from a keel node at the entrance of a coronary artery, namely from a discrete point where the aorta and the coronary artery intersect, traversing the keel node to a first bifurcation point according to the index relation of the keel node of the coronary artery, acquiring and recording the sequence of sub-nodes of the first bifurcation point, and storing the sequence in the matrix B. Taking the first bifurcation point containing two child nodes as an example, according to the relationship that the child nodes of the bifurcation point all share one father node, the direction vector Dir _ fast pointing to the father node of the bifurcation point and the direction vector Dir _ son pointing to two first-level child nodes B (1) and B (2) of the bifurcation point are calculated₁，Dir_son₂Since the distance between the keel node and the point is about one pixel (the distance between two pixel points is about 0.3mm), the three vectors can be regarded as being in the same plane. According to the right-hand rule, normal vectors of direction vectors of a bifurcation point pointing to a father node of the bifurcation point and direction vectors of the bifurcation point pointing to two first-level child nodes are respectively calculated and can be respectively expressed by expressions (1) and (2);

positioning the heart Center according to the distribution of the left and right coronary arteries, calculating a direction vector Dir _ Center of a bifurcation point pointing to the sphere Center by taking the coronary artery Center as the sphere Center, and judging the storage positions of the two sub-nodes in the matrix B by calculating dot products a and B of the normal vector and the direction vector of the bifurcation point pointing to the sphere Center; a and b may be represented by expressions (3) and (4), respectively;

when a is less than 0 and less than B, the positions of elements in the matrix B are kept unchanged, and as shown in FIG. 6a, two keel nodes are distributed in a left-right mode;

when B is less than 0 and less than a, the positions of elements in the matrix B are interchanged, and as shown in figure 6a, the two keel nodes are in a left distribution type;

when a is greater than 0 and b is greater than 0, calculating the Dir _ fast and Dir _ son₁And Dir _ son₂Angle, respectively meterExpressions (5) and (6);

if theta is greater than theta₁＞θ₂The positions of the elements in the matrix B remain unchanged; instead, interchanging the element positions in matrix B, as shown in fig. 6B, the two coronary branches are left-distributed;

when a is less than 0 and b is less than 0, the vector Dir _ fast and the vector Dir _ son are calculated₁And Dir _ son₂Included angle theta₁,θ₂: if theta is greater than theta₁＞θ₂Interchanging the element positions in the matrix B; in contrast, the positions of the elements in the matrix B remain unchanged, as shown in fig. 6c, and the two keel nodes are in a right distribution type;

according to the rule, after the positions of the elements in the matrix B are changed, all the remaining bifurcation points are sequentially traversed until all the outlets of the coronary artery are traversed, so that the traversing sequence of the coronary artery branches from top to bottom and from left to right is determined.

Further, the coronary artery branches may be named based on their spatial position order;

the coronary artery trunk is named C according to the traversal order specified for the coronary artery branches above_mThe other branches of the coronary artery are named according to a certain rule in the left-right order of the determined branches of the coronary artery, and can be represented by expression (7);

where m is the naming attribute of the last branch, n-1 denotes the left branch, n-2 denotes the right branch, and all keels that thus circulate to all coronary branches are named, as shown in fig. 7;

first, the coronary artery entrance keel node is named as attribute C₀When the number of the keel nodes is 0, sequentially traversing all the rest keel nodes of the main trunk, and sequentially inheriting the naming attribute of the father node of each keel node;

secondly, when the keel traverses from the main trunk to the first bifurcation point, the left branch L of the first bifurcation point is appointed according to the determined traversal sequence of the coronary artery branches from top to bottom and from left to right₀₁The first keel node grade is C₀₁＝C₀×10+1＝1Right branch R₀₂The first keel joint is named as C₀₂＝C₀X 10+2 ═ 2. All the rest keel nodes of the branch inherit the name attribute of the father node of the branch in sequence;

finally, when branch L is traversed subsequently₀₁When a bifurcation point is encountered, according to the traversal sequence of the bifurcation point of the coronary artery branches based on the left to the right of the heart, a left branch under the bifurcation point is designated as C₀₁₁＝C₀₁X 10+1 ═ 11, right branch rating C₀₁₂＝C₀₁X 10+2 ═ 12; likewise, branch R₀₂Branches after the rear bifurcation point are all according to branch L₀₁The cases are named, namely C₀₂₁＝C₀₂×10+1＝21，C₀₂₂＝C₀₂X 10+2 ═ 22, this loop continues until the entire coronary keel node is traversed, completing the named coronary branch as shown in fig. 7.

The first determining module 132 is configured to determine, according to the hierarchical relationship of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each centerline, the blood flow of each coronary artery branch by using a preset allocation rule;

here, the total blood volume of the coronary artery may be assigned to each coronary artery branch according to a preset assignment rule. The preset allocation rule can be determined according to the blood allocation relation of the parent coronary artery branch and the child coronary artery branch;

furthermore, the mass of the left ventricular myocardium can be calculated from the myocardium of the patient obtained by organ separation, and the blood flow of the whole coronary artery can be expressed by expression (8) according to the law of the different growth rate between the coronary blood flow and the myocardial mass;

wherein Q is_corIs the total coronary blood flow; q₀A constant coefficient, which can be taken as 5.4; m_myoLeft ventricular myocardial mass;

the profile of the coronary artery includes: left dominant, balanced, and right dominant; determining the blood flow Q of the left coronary artery from the total blood flow of the whole coronary artery_{cor_left}Blood flow Q to the right coronary artery_{cor_right}The ratio of the two is respectively 8: 2. 7.5: 2.5 and 7: 3. for example, if the coronary artery profile is the right dominant profile, then the coronary left and right branch flow distribution is: q_{cor_left}＝70％Q_cor，Q_{cor_right}＝30％Q_cor；

In combination with the poisson law, the blood flow in a coronary artery branch is proportional to the third power of the corresponding branch diameter, and can be expressed by expression (9);

wherein Q is the intravascular flow, d is the diameter of the blood vessel, mu is the hemodynamic viscosity coefficient, and lambda is a proportionality constant representing the energy consumed by the metabolism of the blood vessel per unit volume;

determining respective blood flow volumes of a left coronary artery branch and a right coronary artery branch according to the proportion of preset left coronary artery blood flow volume and preset right coronary artery blood flow volume in total blood flow volumes of coronary arteries;

the blood flow of each coronary branch is expressed by expression (10);

wherein d is_mnRepresenting the diameters, Q, of the sub-coronary branches belonging to the same parent coronary branch at the root node position of the discrete point of the respective corresponding centerline_mRepresenting the total blood flow of the parent coronary artery branch, m representing the parent coronary artery branch, n representing different child coronary artery branches of the m parent coronary artery branches;

taking the bifurcation of the main coronary artery into two sub-coronary artery branches as an example, d₀Is the diameter of the main coronary artery, d₀₁And d₀₂The diameters of the coronary artery branches corresponding to the two primary sub-nodes under the first bifurcation point respectively;

calculating the total blood flow of left (right) coronary artery according to the distribution pattern of coronary artery branches, i.e. main trunk l_mBlood flow volume Q_m(m ═ 0). The other branch flow of the coronary artery is distributed according to the left and right branch flow of the judged coronary artery according to a certain rule under one bifurcation, and the flow volume of the two sub-coronary artery branches can be expressed by an expression (11);

wherein, m is the naming attribute of the last branch, n-1 represents the left branch, n-2 represents the right branch, and the flow is circulated to all the coronary artery branches;

according to the classification of coronary artery branches and the distribution rule of coronary artery blood flow from top to bottom, the coronary artery branch diameters of the second nodes of the left branch and the right branch under the first bifurcation point are respectively obtained, and the branch l is obtained by calculation₀₁And l₀₂The blood flow volume of (c) can be expressed by expressions (12) and (13), respectively;

branch l₀₁Bifurcating to obtain branch l₀₁₁And l₀₁₂According to the same distribution rule, calculating to obtain branch l₀₁₁And l₀₁₂The blood flow volume of (c) can be represented by expressions (14) and (15), respectively;

likewise, branch l₀₂Bifurcating to obtain branch l₀₂₁And l₀₂₂According to the same distribution rule, calculating to obtain branch l₀₂₁And l₀₂₂The blood flow volume of (c) can be expressed by expressions (16) and (17), respectively;

if branch l₀₁₁、l₀₁₂、l₀₂₁And l₀₂₂If there is a further bifurcation, the blood flow of the next branch is distributed step by step according to the diameter of the bifurcation according to the above coronary artery grading principle, and the circulation is continued until the bifurcation does not exist in the branch, namely the outlet of the branch is the outlet of the coronary artery branch, and the blood flow corresponding to the branch is the blood flow of the outlet of the coronary artery branch.

Further, the device further comprises a correction module 134, wherein the correction module 134 is configured to perform linear fitting on the coronary artery branch diameter corresponding to each discrete point on the central line of the coronary artery branch by using a preset fitting rule, so as to obtain a first diameter fitting curve; when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule;

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value; performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve; and when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule. (ii) a

Here, the discrete point at the intersection position of the centerline root is a discrete point at the intersection position of the parent coronary artery branch and the child coronary artery branch and at the intersection position of the child coronary artery branch.

Specifically, the comparison of the coronary artery branch center line extracted from the three-dimensional coronary artery point cloud, that is, the coronary artery branch keel and the original three-dimensional coronary artery point cloud, shows that the diameter obtained may be inaccurate due to the fact that the calculation difficulty is large, and the extracted equivalent diameter is smaller than the real coronary artery branch diameter due to the fact that the concentration of the contrast agent at the tail end of the outlet branch is reduced. In addition, it was found from the three-dimensional coronary artery model reconstructed from the CTA image that stenosis may occur in the coronary artery branches at the bifurcation root. If the diameter of the bifurcation is directly taken to distribute the flow of the coronary artery, a large error may be generated, which causes inaccurate calculation of the microcirculation resistance at the tail end of the coronary artery branch, and further causes inaccurate calculation of the FFR. The method can be used for repairing the stenosis condition at the crossing position by determining the position of the coronary artery branch stenosis;

therefore, preferably, before the linear fitting can be performed on the coronary branch diameter corresponding to each discrete point on the central line of the coronary branch, the method further includes: according to a preset elimination rule, eliminating discrete points with preset lengths of coronary artery branches; the preset elimination rule can be set according to the actual condition of the coronary artery model, and the intersection points and/or the tail ends of the coronary artery branches are eliminated; the preset length can be set according to the abnormal condition of the coronary artery branch, such as 1mm or 2 mm;

specifically, abnormal points at the head and the tail of the coronary artery branch are removed. Comparing the keel nodes at the bifurcation with the bifurcation areas of the real coronary branches, the finding that the main trunk of the coronary branch has about 1mm keel nodes, and the bifurcation branches have about 2mm keel nodes in the bifurcation triangular areas is that the real coronary branch bifurcations are connected with the main trunk of the coronary branch. To coronary artery branch trunk, reject the fossil fragments node in the terminal 1mm, to inside branch, the fossil fragments node in 2mm and 1mm is rejected respectively to the head and the tail, to export branch, reject equally the fossil fragments node in head and the tail 2mm and 1mm, as new branch fossil fragments node.

Further, performing EMD on the coronary artery branch diameter with the length larger than the preset branch length, removing the mode with the maximum fluctuation when the EMD result is larger than the preset mode, and adding the residual mode data to determine the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch;

specifically, the equivalent diameter of the coronary branch keel node is filtered. For coronary artery with longer branches, namely coronary artery branches with length larger than the preset branch length, EMD is respectively carried out on equivalent diameters of different branch coronary artery branches by using an EMD method, different modes are generated after decomposition, for coronary artery branches with length smaller than or equal to two modes, the branch diameters are kept unchanged, and the Diameter sequence is recorded as Diameter_emd(ii) a Otherwise, removing the mode with the maximum fluctuation, and adding the residual mode data to obtain a new coronary artery branch keel Diameter sequence Diameter_emd(ii) a Wherein, 20 keel nodes are taken according to the preset branch length. For coronary artery branches with keel nodes less than or equal to 20 nodes, filtering is not carried out, and Diameter sequences are recorded_emd；

Here, the performing linear fitting on the coronary artery branch diameter corresponding to each discrete point by using the preset fitting rule includes: linearly fitting the diameters of the coronary artery branches corresponding to each discrete point, and expressing a curve obtained by fitting by using the following expression: the first and second diameter-fitted curves may be fitted using the same fitting method; the first diameter fitting curve and the second diameter fitting curve can adopt the same form of fitting tableAn expression; in general, for normal coronary branches, the diameter from the bifurcation to the end is a decreasing series, i.e., the slope of the fitting function is less than 0; firstly, the Diameter distribution of coronary artery branches of different branches can be fitted to obtain a first Diameter fitting curve Diameter_1polyfitThe fitted functions are linear functions and can be represented by expression (18);

wherein, Distance_emdRepresenting the bit order, p, of each discrete point on the central line₁(1) As the slope of the fitted function, p₁(2) Representing the intercept of the fitting function, p₁(1) And p₁(2) Are each p₁＝polyfit(Distance_emd,Diameter_emd1) two constants obtained by fitting, Diameter_emdThe sequence of coronary branch diameters corresponding to each discrete point is represented. The polyfit () represents a fitting function;

when the slope p of the fitting function₁(1) When the diameter is more than 0, as shown in fig. 8, the stenosis condition of the coronary artery branches at the intersection can be preliminarily determined, and the diameter of the coronary artery branch corresponding to the discrete point at the intersection position of the root of the central line is repaired according to a preset repairing rule; the set repairing rule can be determined according to the diameter distribution of coronary artery branches, and the diameters corresponding to the discrete points at the intersection positions can be repaired by adopting the diameters of the adjacent discrete points.

Further, the coronary artery branch diameter corresponding to the discrete point at the central line root intersection position can be determined by adopting an expression (19);

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe method comprises the steps of representing the coronary artery branch diameter corresponding to the last discrete point at the tail end of the central line of the same coronary artery branch, representing the position of the last discrete point by n, and representing the coronary artery branch diameter difference of preset adjacent discrete points by gamma. When the interval of the discrete points is set to be 0.25 mm-0.75 mm, the value range of gamma can be set to be 0.0005 mm-0.0015 mm, and when the interval of the discrete points is 0.5mm, the value range of gamma is 0.001 mm;

when the slope p of the fitting function₁(1) When the number is less than 0, the intersection of the coronary artery branches can be preliminarily determinedThe fork is not narrow and does not need to be repaired; however, it cannot be excluded that there is a wide stenosis in the middle of the coronary branches, and that the slope p of the function is such that a stenosis occurs in the middle of the coronary branches₁(1) Less than 0 may also occur; in order to eliminate the influence of the diameter of the stenosis position on the fitting function, the first-time fitting function can be used for calculating the stenosis rate of the current coronary artery branch fitting function;

can utilize Diameter_1polyfitAnd Diameter_emdIs divided by Diameter_1polyfitAs the first diameter-fitted curve stenosis rate at the coronary artery branch stenosis, the first diameter-fitted curve stenosis rate can be expressed by expression (20);

due to the function slope p₁(1) < 0, it is possible to preliminarily locate the position where the coronary artery branch stenosis occurs not to occur at the root of the bifurcation. For branches where no stenosis is present or where the degree of stenosis is low, the fitted keel diameter function can be considered as the diameter distribution of the ideal coronary branches, whereas for coronary branches where a severe stenosis is present in the middle, the fitted function is not very close to the diameter distribution of the real coronary branches due to the presence of stenosis. Therefore, discrete points with stenosis rate larger than a first preset stenosis rate threshold value, such as 50%, can be eliminated to obtain a new Diameter coronary artery branch Diameter sequence Diameter_newFitting the Diameter coronary artery branch Diameter without discrete points by adopting a fitting method of fitting the same first Diameter fitting curve to obtain a second Diameter fitting curve Diameter_2polyfitCombined with Diameter_newAnd Distance_newFitting to obtain Diameter_2polyfitAnd can be represented by expression (21);

wherein p is₂(1) As the slope of the fitted function, p₂(2) Representing the intercept of the fitting function, p₂(1) And p₂(2) Are each p₂＝polyfit(Distance_new,Diameter_new1) two constants obtained by fitting, Distance_newRepresents the bit order sequence for each discrete point on the centerline, i.e., the bit order sequence for each discrete point on the centerline. The polyfit () represents a fitting function; herein is expressedEquations (18) and (21) are the same calculation method except that the variables are different.

Reuse of Diamete_2polyfitAnd Diameter_newIs divided by diameter_2polyfitThe stenosis rate, which is the fitted curve of the second diameter at the stenosis of the coronary branch, can be expressed by expression (22);

here, the stenosis rate of the first diameter-fitted curve and the stenosis rate of the second diameter-fitted curve respectively represent the stenosis rates of the coronary artery branches before and after passing through the discrete point where the rejection stenosis rate is greater than the first preset stenosis rate threshold. After two fits, for the stenosis rate at the intersection position, if it is greater than a second preset stenosis rate threshold, it is determined that stenosis has occurred. According to a preset repairing rule, repairing the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root of the central line; the repairing method is consistent with the method for determining the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root part of the central line by adopting the expression (19), and the details are not repeated.

Therefore, the coronary artery branch with stenosis at the root of the coronary artery branch is repaired to obtain the new equivalent diameter of the bifurcation, and the blood flow of the coronary artery branch is directly distributed according to the repair, so that the accuracy of the flow distribution of the coronary artery branch is improved.

Furthermore, the stenosis of the coronary artery branch can be marked for the reference of the medical staff. Here, the stenosis rate maximum values corresponding to different coronary artery branches may be searched, and it is generally clinically concerned that the main coronary artery branches have a stenosis rate higher than a certain threshold, for example, 50%, and therefore, the maximum value having a stenosis rate smaller than the threshold is removed from the maximum values of the coronary artery branches, for the maximum value having a stenosis rate larger than the threshold, the maximum value coordinate is obtained and positioned on the coronary artery branch keel, the coronary artery branch keel nodes are searched forward and backward from the stenosis coordinate point, respectively, until the corresponding stenosis rate is smaller than or equal to a certain value, for example, 10%, the coronary artery branch keel node farthest from the stenosis point forward and backward is marked and recorded, and the distance of the keel nodes at both ends along the keel direction is calculated as the stenosis length StenosisLength. Stenosis information can be provided to medical personnel for reference.

The second determining module 133 is configured to determine a microcirculation resistance of a coronary artery branch corresponding to the preset blood outlet according to the blood flow volume of each coronary artery branch;

here, the resistance of the downstream coronary branch microcirculation corresponding to different branch outlets of the normal coronary artery in the resting state is calculated by combining the relationship among the pressure, the blood flow and the vascular resistance in the resting state of the coronary artery. The preset blood outlet can be determined according to the diameter of the tail end of the coronary artery branch, the diameter of the blood outlet can be preset, the tail end of the coronary artery branch is smaller than the diameter of the preset blood outlet, and the coronary artery branch is determined to be the coronary artery branch corresponding to the preset blood outlet. The diameter of the preset blood outlet can be 1-2 mm.

Preferably, the mean aortic pressure is subtracted from the epicardial coronary pressure drop, and then the central venous pressure is subtracted to obtain the pressure difference from the end of the coronary artery branch to the end of the vein; dividing the coronary artery pressure by the quotient of the blood flow volume of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a resting state;

specifically, under the condition that an epicardial blood vessel is not narrowed, the epicardial coronary artery pressure drop of a normal person is clinically measured to be 1-2 mmHg, 1mmHg can be taken, and the coronary artery inlet pressure is taken as the mean aortic pressure P_a90mmHg, distal pressure of coronary microcirculation, i.e. central venous pressure P_d6.25mmHg, the pressure difference Δ P from the end of the coronary branch to the end of the vein is thus equal to ((P)_a-1)-P_d) 82.75 mmHg. According to Δ P ═ Q × R_rQ is the blood flow of the coronary artery branch corresponding to the preset blood outlet, and the microcirculation resistance of the tail end of each branch is ensured under the resting state

Finally, according to the microcirculation resistance of the coronary artery branch in the preset rest state and the coronary artery in the hyperemia stateThe proportion coefficient of the branch microcirculation resistance obtains the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a congestion state; calculating the microcirculation resistance R of the branch end of the coronary artery in a hyperemia state according to a preset proportionality coefficient such as 0.24_h＝0.24R_r. Thus, the calculation of the microcirculation resistance at the end of each branch coronary artery is completed.

Based on this method, the classification and resistance display of the real coronary branches is shown in fig. 8, and the coronary FFR distribution is obtained by CFD calculation.

Fig. 10 shows a table of FFR calculation results of the left coronary branch obtained by performing FFR calculation with respect to the naming and resistance maps of the real coronary keel points shown in fig. 9. The FFR calculation results of the left and right coronary branches obtained by performing the FFR calculation with respect to the naming and resistance maps of the real coronary keel points after the diameter of the cross-site discrete points is restored in fig. 11 are shown in fig. 12.

Therefore, the flow of each branch of the coronary artery is accurately calculated according to the diameter of the root of the branch at the bifurcation of the coronary artery by a step-by-step distribution method, the accurate resistance of each outlet of each branch of the coronary artery is obtained, and the accuracy of the calculation result of the FFRCT technology is improved.

In practical applications, the model processing module 131, the first determining module 132, the second determining module 133 and the modifying module 134 may be implemented by a CPU, a Microprocessor (MCU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), or the like in the FFRCT processing system.

A storage medium is provided in an embodiment of the present invention, and has an executable program stored thereon, and when the executable program is executed by a processor, the method for determining coronary artery microcirculation resistance is implemented, as shown in fig. 1, the method includes:

step 101: according to the three-dimensional image model of the coronary artery, establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

here, coronary artery image data can be acquired through CTA and other methods, a three-dimensional image model of a coronary artery is established through setting a threshold, selecting a certain number of isosurface, establishing a connected domain and the like, and a coronary artery lattice cloud is extracted. The coronary artery branch may refer to the whole vessel branch of the whole coronary artery, such as the left coronary artery, the right coronary artery, the main coronary artery and the bifurcation coronary artery of the left and right coronary arteries;

specifically, CTA image data is shown in fig. 2. The CTA image data can be imported into three-dimensional reconstruction software, with the lighter regions representing essentially the aorta, the lumen of the major coronary arteries, and the darker regions representing the myocardium and other tissue of the patient's heart; setting an image parameter threshold, selecting a certain number of isosurfaces, establishing a connected domain, reconstructing to generate a three-dimensional image model formed by triangular meshes, and performing surface smoothing according to a Laplace algorithm to finally obtain the three-dimensional geometric model containing the heart, the aorta and the coronary artery as shown in FIG. 3. In order to better obtain a coronary artery three-dimensional model, methods such as interpolation, smoothing and the like can be adopted to process calcified plaque of coronary artery and carry out smoothing and hole filling;

setting parameter thresholds such as image brightness and contrast, identifying, separating a coronary artery model comprising a plurality of main coronary arteries such as LAD (coronary artery occlusion), LCX (left-handed control) artery, RCA (Rac artery occlusion) artery and branches thereof from segmented aorta and coronary arteries shown in a three-dimensional geometric model comprising the heart, the aorta and the coronary arteries in FIG. 4a, and extracting a lattice cloud model of the coronary artery model shown in FIG. 4b, wherein the lattice cloud is a discretization form of the coronary artery model;

after the coronary artery lattice cloud model is obtained, a central line which is formed by discrete points and corresponds to each coronary artery branch can be extracted, and the hierarchical relation of each coronary artery branch can be determined according to the connection relation of each central line, such as the tree structure of the central line; the central line can be formed by connecting discrete points, the interval of the discrete points can be preset, and the spatial distance of the interval can be determined by combining the spatial linear distance, the spatial angle and the like. For example, the discrete point space linear distance interval may be set to 0.25mm to 0.75mm, such as 0.5 mm. The centerline of the coronary artery branch is commonly referred to as the coronary artery branch keel and the discrete points making up the centerline may be commonly referred to as the coronary artery branch keel nodes.

Furthermore, the coronary artery branch hierarchical relationship can be determined according to the cross connection relationship of discrete points of the central line of each coronary artery branch and the preset blood flowing direction; the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch; the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch;

here, the parent coronary artery branch and the child coronary artery branch may have a plurality of levels, the parent coronary artery branch may be a child coronary artery branch of an upper level, and the child coronary artery branch may be a parent coronary artery branch of a lower level; the hierarchical relationship of coronary artery branches may be determined according to a blood flow direction, including a parent coronary artery branch and a child coronary artery branch, typically the child coronary artery branch is connected with the parent coronary artery branch by a crossing point, and the blood flow direction is from the parent coronary artery branch to the child coronary artery branch.

In practical application, as shown in fig. 4a and 4b, a coronary artery lattice cloud can be extracted, the lattice cloud is converted into a binary high-dimensional matrix, a connected domain is calculated, a smaller connected domain is removed, a skeleton is extracted by using a coronary artery skeleton extraction algorithm, and a keel node index is established. The keel nodes are discrete points of the central line. The keel node index is the relationship between a child node and a father node;

specifically, firstly, converting a dot matrix cloud into a binary high-dimensional matrix, calculating a connected domain, and rejecting a smaller connected domain, wherein the connected domain with less than 100 pixel points is generally rejected;

secondly, extracting bones by using a coronary artery bone extraction algorithm, marking the physical coordinate positions of keel nodes, and recording the positions in the first three columns in a matrix A, wherein the total number of the keel nodes is N, and the spatial position of the ith node is p_i＝(x_i,y_i,z_i) And (4) showing. Calculating the equivalent area A of coronary artery on each node_iEquivalent diameter d_iDirection of blood flow v_i(first derivative of spatial position) equi-geometric informationAnd (4) information. Equivalent area refers to the area enclosed by a perpendicular section to the coronary arteries; the equivalent diameter is calculated by the formula

Calculating the blood flow direction according to respective mathematical definition, adding all data into the matrix A according to the keel coordinate position, and directly calling the subsequent calculation;

finally, find node i in the reverse direction of blood flow-v_iThe current node is called a child node, which indicates that the blood flow direction is from the parent node to the child node, and the node is a discrete point forming the centerline of the coronary artery branch. It should be noted that: the blood flow entry point has no parent node, the blood flow exit point has no child node, and the bifurcation point is a parent node of the plurality of child nodes. And searching a branch path from the inlet to the outlet according to the spatial relationship between the child node and the parent node, namely searching the parent node of each node from the outlet until the inlet node of the coronary artery. The coronary artery keel nodes traverse sequentially from the entrance to the first-level branch, the second-level branch and the like until all the exits, so that the program searches all the exits from the coronary artery entrance to obtain a coronary artery branch hierarchical relation graph shown in fig. 5, namely keel indexes. The outlet of the coronary artery can be preset, for example, the position of the tail end of a coronary artery branch with the diameter of 1-2 mm is set as the outlet of the coronary artery; wherein the bifurcation is the intersection of the coronary branches.

In practical application, the spatial position relationship of the coronary artery branches can be established according to the arrangement of the coronary artery branches and the preset sequence, and the coronary artery branches are named according to the preset naming rule; thus, the coronary artery branches are mathematically and geometrically graded and named from top to bottom and from left to right, and the problem that the flow at the tail end of the coronary artery cannot be regularly and programmatically evaluated before FFRCT calculation is solved;

specifically, according to the above-mentioned coronary artery keel node index relationship, a coronary artery branch bifurcation point is found, and the sequence of traversing the sub-nodes of the coronary artery branch bifurcation point along the coronary artery from top to bottom and from left to right along the heart center is determined;

based on the keel data matrix A, from a keel node at the entrance of a coronary artery, namely from a discrete point where the aorta and the coronary artery intersect, traversing the keel node to a first bifurcation point according to the index relation of the keel node of the coronary artery, acquiring and recording the sequence of sub-nodes of the first bifurcation point, and storing the sequence in the matrix B. Taking the first bifurcation point containing two child nodes as an example, according to the relationship that the child nodes of the bifurcation point all share one father node, the direction vector Dir _ fast pointing to the father node of the bifurcation point and the direction vector Dir _ son pointing to two first-level child nodes B (1) and B (2) of the bifurcation point are calculated₁，Dir_son₂Since the distance between the keel node and the point is about one pixel (the distance between two pixel points is about 0.3mm), the three vectors can be regarded as being in the same plane. According to the right-hand rule, normal vectors of direction vectors of a bifurcation point pointing to a father node of the bifurcation point and direction vectors of the bifurcation point pointing to two first-level child nodes are respectively calculated and can be respectively expressed by expressions (1) and (2);

positioning the heart Center according to the distribution of the left and right coronary arteries, calculating a direction vector Dir _ Center of a bifurcation point pointing to the sphere Center by taking the coronary artery Center as the sphere Center, and judging the storage positions of the two sub-nodes in the matrix B by calculating dot products a and B of the normal vector and the direction vector of the bifurcation point pointing to the sphere Center; a and b may be represented by expressions (3) and (4), respectively;

when a is less than 0 and less than B, the positions of elements in the matrix B are kept unchanged, and as shown in FIG. 6a, two keel nodes are distributed in a left-right mode;

when B is less than 0 and less than a, the positions of elements in the matrix B are interchanged, and as shown in figure 6a, the two keel nodes are in a left distribution type;

when a is greater than 0 and b is greater than 0, calculating the Dir _ fast and Dir _ son₁And Dir _ son₂The included angles are respectively expressed by expressions (5) and (6);

if theta is greater than theta₁＞θ₂The positions of the elements in the matrix B remain unchanged; instead, interchanging the element positions in matrix B, as shown in fig. 6B, the two coronary branches are left-distributed;

when a <0, b < 0, and calculating the Dir _ fast and Dir _ son vectors₁And Dir _ son₂Included angle theta₁,θ₂: if theta is greater than theta₁＞θ₂Interchanging the element positions in the matrix B; in contrast, the positions of the elements in the matrix B remain unchanged, as shown in fig. 6c, and the two keel nodes are in a right distribution type;

according to the rule, after the positions of the elements in the matrix B are changed, all the remaining bifurcation points are sequentially traversed until all the outlets of the coronary artery are traversed, so that the traversing sequence of the coronary artery branches from top to bottom and from left to right is determined.

Further, the coronary artery branches may be named based on their spatial position order;

the coronary artery trunk is named C according to the traversal order specified for the coronary artery branches above_mThe other branches of the coronary artery are named according to a certain rule in the left-right order of the determined branches of the coronary artery, and can be represented by expression (7);

where m is the naming attribute of the last branch, n-1 denotes the left branch, n-2 denotes the right branch, and all keels that thus circulate to all coronary branches are named, as shown in fig. 7;

first, the coronary artery entrance keel node is named as attribute C₀When the number of the keel nodes is 0, sequentially traversing all the rest keel nodes of the main trunk, and sequentially inheriting the naming attribute of the father node of each keel node;

secondly, when the keel traverses from the main trunk to the first bifurcation point, the left branch L of the first bifurcation point is appointed according to the determined traversal sequence of the coronary artery branches from top to bottom and from left to right₀₁The first keel node grade is C₀₁＝C₀X 10+1 ═ 1, right branch R₀₂The first keel joint is named as C₀₂＝C₀X 10+2 ═ 2. All the rest keel nodes of the branch inherit the name attribute of the father node of the branch in sequence;

finally, when branch L is traversed subsequently₀₁When encountering a bifurcation point, pressAssigning a left branch under a bifurcation point to be named as C according to the traversal order of the bifurcation point of coronary artery branches from left to right based on the heart₀₁₁＝C₀₁X 10+1 ═ 11, right branch rating C₀₁₂＝C₀₁X 10+2 ═ 12; likewise, branch R₀₂Branches after the rear bifurcation point are all according to branch L₀₁The cases are named, namely C₀₂₁＝C₀₂×10+1＝21，C₀₂₂＝C₀₂X 10+2 ═ 22, this loop continues until the entire coronary keel node is traversed, completing the named coronary branch as shown in fig. 7.

Step 102: determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line;

here, the total blood volume of the coronary artery may be assigned to each coronary artery branch according to a preset assignment rule. The preset allocation rule can be determined according to the blood allocation relation of the parent coronary artery branch and the child coronary artery branch;

furthermore, the mass of the left ventricular myocardium can be calculated from the myocardium of the patient obtained by organ separation, and the blood flow of the whole coronary artery can be expressed by expression (8) according to the law of the different growth rate between the coronary blood flow and the myocardial mass;

wherein Q is_corIs the total coronary blood flow; q₀A constant coefficient, which can be taken as 5.4; m_myoLeft ventricular myocardial mass;

the profile of the coronary artery includes: left dominant, balanced, and right dominant; determining the blood flow Q of the left coronary artery from the total blood flow of the whole coronary artery_{cor_left}Blood flow Q to the right coronary artery_{cor_right}The ratio of the two is respectively 8: 2. 7.5: 2.5 and 7: 3. for example, if the coronary artery profile is the right dominant profile, then the coronary left and right branch flow distribution is: q_{cor_left}＝70％Q_cor，Q_{cor_right}＝30％Q_cor；

In combination with the poisson law, the blood flow in a coronary artery branch is proportional to the third power of the corresponding branch diameter, and can be expressed by expression (9);

wherein Q is the intravascular flow, d is the diameter of the blood vessel, mu is the hemodynamic viscosity coefficient, and lambda is a proportionality constant representing the energy consumed by the metabolism of the blood vessel per unit volume;

determining respective blood flow volumes of a left coronary artery branch and a right coronary artery branch according to the proportion of preset left coronary artery blood flow volume and preset right coronary artery blood flow volume in total blood flow volumes of coronary arteries;

the blood flow of each coronary branch is expressed by expression (10);

wherein d is_mnRepresenting the diameters, Q, of the sub-coronary branches belonging to the same parent coronary branch at the root node position of the discrete point of the respective corresponding centerline_mRepresenting the total blood flow of the parent coronary artery branch, m representing the parent coronary artery branch, n representing different child coronary artery branches of the m parent coronary artery branches;

taking the bifurcation of the main coronary artery into two sub-coronary artery branches as an example, d₀Is the diameter of the main coronary artery, d₀₁And d₀₂The diameters of the coronary artery branches corresponding to the two primary sub-nodes under the first bifurcation point respectively;

calculating the total blood flow of left (right) coronary artery according to the distribution pattern of coronary artery branches, i.e. main trunk l_mBlood flow volume Q_m(m ═ 0). The other branch flow of the coronary artery is distributed according to the left and right branch flow of the judged coronary artery according to a certain rule under one bifurcation, and the flow volume of the two sub-coronary artery branches can be expressed by an expression (11);

wherein, m is the naming attribute of the last branch, n-1 represents the left branch, n-2 represents the right branch, and the flow is circulated to all the coronary artery branches;

according to the classification of coronary artery branches and the distribution rule of coronary artery blood flow from top to bottom, respectively obtaining the second nodes of the left branch and the right branch under the first bifurcation pointThe diameter of the coronary artery branch is calculated to obtain branch l₀₁And l₀₂The blood flow volume of (c) can be expressed by expressions (12) and (13), respectively;

branch l₀₁Bifurcating to obtain branch l₀₁₁And l₀₁₂According to the same distribution rule, calculating to obtain branch l₀₁₁And l₀₁₂The blood flow volume of (c) can be represented by expressions (14) and (15), respectively;

likewise, branch l₀₂Bifurcating to obtain branch l₀₂₁And l₀₂₂According to the same distribution rule, calculating to obtain branch l₀₂₁And l₀₂₂The blood flow volume of (c) can be expressed by expressions (16) and (17), respectively;

if branch l₀₁₁、l₀₁₂、l₀₂₁And l₀₂₂If there is a further bifurcation, the blood flow of the next branch is distributed step by step according to the diameter of the bifurcation according to the above coronary artery grading principle, and the circulation is continued until the bifurcation does not exist in the branch, namely the outlet of the branch is the outlet of the coronary artery branch, and the blood flow corresponding to the branch is the blood flow of the outlet of the coronary artery branch.

Further, a preset fitting rule is adopted to perform linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line to obtain a first diameter fitting curve; when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule;

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value; performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve; and when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule. (ii) a

Here, the discrete point at the intersection position of the centerline root is a discrete point at the intersection position of the parent coronary artery branch and the child coronary artery branch and at the intersection position of the child coronary artery branch.

Specifically, the comparison of the coronary artery branch center line extracted from the three-dimensional coronary artery point cloud, that is, the coronary artery branch keel and the original three-dimensional coronary artery point cloud, shows that the diameter obtained may be inaccurate due to the fact that the calculation difficulty is large, and the extracted equivalent diameter is smaller than the real coronary artery branch diameter due to the fact that the concentration of the contrast agent at the tail end of the outlet branch is reduced. In addition, it was found from the three-dimensional coronary artery model reconstructed from the CTA image that stenosis may occur in the coronary artery branches at the bifurcation root. If the diameter of the bifurcation is directly taken to distribute the flow of the coronary artery, a large error may be generated, which causes inaccurate calculation of the microcirculation resistance at the tail end of the coronary artery branch, and further causes inaccurate calculation of the FFR. The method can be used for repairing the stenosis condition at the crossing position by determining the position of the coronary artery branch stenosis;

therefore, preferably, before the linear fitting can be performed on the coronary branch diameter corresponding to each discrete point on the central line of the coronary branch, the method further includes: according to a preset elimination rule, eliminating discrete points with preset lengths of coronary artery branches; the preset elimination rule can be set according to the actual condition of the coronary artery model, and the intersection points and/or the tail ends of the coronary artery branches are eliminated; the preset length can be set according to the abnormal condition of the coronary artery branch, such as 1mm or 2 mm;

specifically, abnormal points at the head and the tail of the coronary artery branch are removed. Comparing the keel nodes at the bifurcation with the bifurcation areas of the real coronary branches, the finding that the main trunk of the coronary branch has about 1mm keel nodes, and the bifurcation branches have about 2mm keel nodes in the bifurcation triangular areas is that the real coronary branch bifurcations are connected with the main trunk of the coronary branch. To coronary artery branch trunk, reject the fossil fragments node in the terminal 1mm, to inside branch, the fossil fragments node in 2mm and 1mm is rejected respectively to the head and the tail, to export branch, reject equally the fossil fragments node in head and the tail 2mm and 1mm, as new branch fossil fragments node.

Further, performing EMD on the coronary artery branch diameter with the length larger than the preset branch length, removing the mode with the maximum fluctuation when the EMD result is larger than the preset mode, and adding the residual mode data to determine the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch;

specifically, the equivalent diameter of the coronary branch keel node is filtered. For coronary artery with longer branches, namely coronary artery branches with length larger than the preset branch length, EMD is respectively carried out on equivalent diameters of different branch coronary artery branches by using an EMD method, different modes are generated after decomposition, for coronary artery branches with length smaller than or equal to two modes, the branch diameters are kept unchanged, and the Diameter sequence is recorded as Diameter_emd(ii) a Otherwise, removing the mode with the maximum fluctuation, and adding the residual mode data to obtain a new coronary artery branch keel Diameter sequence Diameter_emd(ii) a Wherein, 20 keel nodes are taken according to the preset branch length. For coronary artery branches with keel nodes less than or equal to 20 nodes, filtering is not carried out, and Diameter sequences are recorded_emd；

Here, the performing linear fitting on the coronary artery branch diameter corresponding to each discrete point by using the preset fitting rule includes: linearly fitting the diameters of the coronary artery branches corresponding to each discrete point, and expressing a curve obtained by fitting by using the following expression: the first and second diameter-fitted curves may be fitted using the same fitting method; the first diameter fitting curve and the second diameter fitting curve can adopt fitting expressions in the same form; in general, for normal coronary branches, the diameter from the bifurcation to the end is a decreasing series, i.e., the slope of the fitting function is less than 0; firstly, the Diameter distribution of coronary artery branches of different branches can be fitted to obtain a first Diameter fitting curve Diameter_1polyfitThe fitted functions are linear functions and can be represented by expression (18);

whereinWherein, Distance_emdRepresenting the bit order, p, of each discrete point on the central line₁(1) As the slope of the fitted function, p₁(2) Representing the intercept of the fitting function, p₁(1) And p₁(2) Are each p₁＝polyfit(Distance_emd,Diameter_emd1) two constants obtained by fitting, Diameter_emdThe sequence of coronary branch diameters corresponding to each discrete point is represented. The polyfit () represents a fitting function;

when the slope p of the fitting function₁(1) When the diameter is more than 0, as shown in fig. 8, the stenosis condition of the coronary artery branches at the intersection can be preliminarily determined, and the diameter of the coronary artery branch corresponding to the discrete point at the intersection position of the root of the central line is repaired according to a preset repairing rule; the set repairing rule can be determined according to the diameter distribution of coronary artery branches, and the diameters corresponding to the discrete points at the intersection positions can be repaired by adopting the diameters of the adjacent discrete points.

Further, the coronary artery branch diameter corresponding to the discrete point at the central line root intersection position can be determined by adopting an expression (19);

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe method comprises the steps of representing the coronary artery branch diameter corresponding to the last discrete point at the tail end of the central line of the same coronary artery branch, representing the position of the last discrete point by n, and representing the coronary artery branch diameter difference of preset adjacent discrete points by gamma. When the interval of the discrete points is set to be 0.25 mm-0.75 mm, the value range of gamma can be set to be 0.0005 mm-0.0015 mm, and when the interval of the discrete points is 0.5mm, the value range of gamma is 0.001 mm;

when the slope p of the fitting function₁(1) When the number is less than 0, the situation that the coronary artery branches are not narrowed at the intersection can be preliminarily determined, and the repair is not needed; however, it cannot be excluded that there is a wide stenosis in the middle of the coronary branches, and that the slope p of the function is such that a stenosis occurs in the middle of the coronary branches₁(1) Less than 0 may also occur; in order to eliminate the influence of the diameter of the stenosis position on the fitting function, the first-time fitting function can be used for calculating the stenosis rate of the current coronary artery branch;

can utilize Diameter_1polyfitAnd Diameter_emdIs divided by Diameter_1polyfitAs the first diameter-fitted curve stenosis rate at the coronary artery branch stenosis, the first diameter-fitted curve stenosis rate can be expressed by expression (20);

due to the function slope p₁(1) < 0, it is possible to preliminarily locate the position where the coronary artery branch stenosis occurs not to occur at the root of the bifurcation. For branches where no stenosis is present or where the degree of stenosis is low, the fitted keel diameter function can be considered as the diameter distribution of the ideal coronary branches, whereas for coronary branches where a severe stenosis is present in the middle, the fitted function is not very close to the diameter distribution of the real coronary branches due to the presence of stenosis. Therefore, discrete points with stenosis rate larger than a first preset stenosis rate threshold value, such as 50%, can be eliminated to obtain a new Diameter coronary artery branch Diameter sequence Diameter_newFitting the diameters of the coronary artery branches after the discrete points are removed by adopting a fitting method of fitting the same first Diameter fitting curve to obtain a second Diameter fitting curve Diameter_2polyfitCombined with Diameter_newAnd Distance_newFitting to obtain Diameter_2polyfitAnd can be represented by expression (21);

wherein p is₂(1) As the slope of the fitted function, p₂(2) Representing the intercept of the fitting function, p₂(1) And p₂(2) Are each p₂＝polyfit(Distance_new,Diameter_new1) two constants obtained by fitting, Distance_newRepresents the bit order sequence for each discrete point on the centerline, i.e., the bit order sequence for each discrete point on the centerline. The polyfit () represents a fitting function; here, expressions (18) and (21) are the same calculation method except that the variables are different.

Reuse of Diamete_2polyfitAnd Diameter_newIs divided by diameter_2polyfitThe stenosis rate of the second diameter-fitted curve as a coronary artery branch can be expressed by expression (22);

here, the stenosis rate of the first diameter-fitted curve and the stenosis rate of the second diameter-fitted curve respectively represent the stenosis rates of the coronary artery branches before and after passing through the discrete point where the rejection stenosis rate is greater than the first preset stenosis rate threshold. After two fits, for the stenosis rate at the intersection position, if it is greater than a second preset stenosis rate threshold, it is determined that stenosis has occurred. According to a preset repairing rule, repairing the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root of the central line; the repairing method is consistent with the method for determining the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root part of the central line by adopting the expression (19), and the details are not repeated.

Therefore, the coronary artery branch with stenosis at the root of the coronary artery branch is repaired to obtain the new equivalent diameter of the bifurcation, and the blood flow of the coronary artery branch is directly distributed according to the repair, so that the accuracy of the flow distribution of the coronary artery branch is improved.

Furthermore, the stenosis of the coronary artery branch can be marked for the reference of the medical staff. Here, the stenosis rate maximum values corresponding to different coronary artery branches may be searched, and it is generally clinically concerned that the main coronary artery branches have a stenosis rate higher than a certain threshold, for example, 50%, and therefore, the maximum value having a stenosis rate smaller than the threshold is removed from the maximum values of the coronary artery branches, for the maximum value having a stenosis rate larger than the threshold, the maximum value coordinate is obtained and positioned on the coronary artery branch keel, the coronary artery branch keel nodes are searched forward and backward from the stenosis coordinate point, respectively, until the corresponding stenosis rate is smaller than or equal to a certain value, for example, 10%, the coronary artery branch keel node farthest from the stenosis point forward and backward is marked and recorded, and the distance of the keel nodes at both ends along the keel direction is calculated as the stenosis length StenosisLength. Stenosis information can be provided to medical personnel for reference.

Step 103, determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch;

here, the resistance of the downstream coronary branch microcirculation corresponding to different branch outlets of the normal coronary artery in the resting state is calculated by combining the relationship among the pressure, the blood flow and the vascular resistance in the resting state of the coronary artery. The preset blood outlet can be determined according to the diameter of the tail end of the coronary artery branch, the diameter of the blood outlet can be preset, the tail end of the coronary artery branch is smaller than the diameter of the preset blood outlet, and the coronary artery branch is determined to be the coronary artery branch corresponding to the preset blood outlet. The diameter of the preset blood outlet can be 1-2 mm.

Preferably, the mean aortic pressure is subtracted from the epicardial coronary pressure drop, and then the central venous pressure is subtracted to obtain the pressure difference from the end of the coronary artery branch to the end of the vein; dividing the coronary artery pressure by the quotient of the blood flow volume of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a resting state;

specifically, under the condition that an epicardial blood vessel is not narrowed, the epicardial coronary artery pressure drop of a normal person is clinically measured to be 1-2 mmHg, 1mmHg can be taken, and the coronary artery inlet pressure is taken as the mean aortic pressure P_a90mmHg, distal pressure of coronary microcirculation, i.e. central venous pressure P_d6.25mmHg, the pressure difference Δ P from the end of the coronary branch to the end of the vein is thus equal to ((P)_a-1)-P_d) 82.75 mmHg. According to Δ P ═ Q × R_rQ is the blood flow of the coronary artery branch corresponding to the preset blood outlet, and the microcirculation resistance of the tail end of each branch is ensured under the resting state

Finally, obtaining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in the hyperemia state according to the proportion coefficient of the microcirculation resistance of the coronary artery branch in the preset rest state and the microcirculation resistance of the coronary artery branch in the hyperemia state; calculating the microcirculation resistance R of the branch end of the coronary artery in a hyperemia state according to a preset proportionality coefficient such as 0.24_h＝0.24R_r. Thus, the calculation of the microcirculation resistance at the end of each branch coronary artery is completed.

Based on this method, the classification and resistance display of the real coronary branches is shown in fig. 8, and the coronary FFR distribution is obtained by CFD calculation.

Fig. 10 shows a table of FFR calculation results of the left coronary branch obtained by performing FFR calculation with respect to the naming and resistance maps of the real coronary keel points shown in fig. 9. The FFR calculation results of the left and right coronary branches obtained by performing the FFR calculation with respect to the naming and resistance maps of the real coronary keel points after the diameter of the cross-site discrete points is restored in fig. 11 are shown in fig. 12.

Therefore, the flow of each branch of the coronary artery is accurately calculated according to the diameter of the root of the branch at the bifurcation of the coronary artery by a step-by-step distribution method, the accurate resistance of each outlet of each branch of the coronary artery is obtained, and the accuracy of the calculation result of the FFRCT technology is improved.

The apparatus for determining coronary artery microcirculation resistance provided by the embodiment of the present invention includes a processor, a memory, and an executable program stored on the memory and capable of being executed by the processor, and when the processor executes the executable program, the method for determining coronary artery microcirculation resistance is executed, as shown in fig. 1, the method includes:

step 101: according to the three-dimensional image model of the coronary artery, establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

here, coronary artery image data can be acquired through CTA and other methods, a three-dimensional image model of a coronary artery is established through setting a threshold, selecting a certain number of isosurface, establishing a connected domain and the like, and a coronary artery lattice cloud is extracted. The coronary artery branch may refer to the whole vessel branch of the whole coronary artery, such as the left coronary artery, the right coronary artery, the main coronary artery and the bifurcation coronary artery of the left and right coronary arteries;

specifically, CTA image data is shown in fig. 2. The CTA image data can be imported into three-dimensional reconstruction software, with the lighter regions representing essentially the aorta, the lumen of the major coronary arteries, and the darker regions representing the myocardium and other tissue of the patient's heart; setting an image parameter threshold, selecting a certain number of isosurfaces, establishing a connected domain, reconstructing to generate a three-dimensional image model formed by triangular meshes, and performing surface smoothing according to a Laplace algorithm to finally obtain the three-dimensional geometric model containing the heart, the aorta and the coronary artery as shown in FIG. 3. In order to better obtain a coronary artery three-dimensional model, methods such as interpolation, smoothing and the like can be adopted to process calcified plaque of coronary artery and carry out smoothing and hole filling;

setting parameter thresholds such as image brightness and contrast, identifying, separating a coronary artery model comprising a plurality of main coronary arteries such as LAD (coronary artery occlusion), LCX (left-handed control) artery, RCA (Rac artery occlusion) artery and branches thereof from segmented aorta and coronary arteries shown in a three-dimensional geometric model comprising the heart, the aorta and the coronary arteries in FIG. 4a, and extracting a lattice cloud model of the coronary artery model shown in FIG. 4b, wherein the lattice cloud is a discretization form of the coronary artery model;

after the coronary artery lattice cloud model is obtained, a central line which is formed by discrete points and corresponds to each coronary artery branch can be extracted, and the hierarchical relation of each coronary artery branch can be determined according to the connection relation of each central line, such as the tree structure of the central line; the central line can be formed by connecting discrete points, the interval of the discrete points can be preset, and the spatial distance of the interval can be determined by combining the spatial linear distance, the spatial angle and the like. For example, the discrete point space linear distance interval may be set to 0.25mm to 0.75mm, such as 0.5 mm. The centerline of the coronary artery branch is commonly referred to as the coronary artery branch keel and the discrete points making up the centerline may be commonly referred to as the coronary artery branch keel nodes.

Furthermore, the coronary artery branch hierarchical relationship can be determined according to the cross connection relationship of discrete points of the central line of each coronary artery branch and the preset blood flowing direction; the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch; the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch;

here, the parent coronary artery branch and the child coronary artery branch may have a plurality of levels, the parent coronary artery branch may be a child coronary artery branch of an upper level, and the child coronary artery branch may be a parent coronary artery branch of a lower level; the hierarchical relationship of coronary artery branches may be determined according to a blood flow direction, including a parent coronary artery branch and a child coronary artery branch, typically the child coronary artery branch is connected with the parent coronary artery branch by a crossing point, and the blood flow direction is from the parent coronary artery branch to the child coronary artery branch.

In practical application, as shown in fig. 4a and 4b, a coronary artery lattice cloud can be extracted, the lattice cloud is converted into a binary high-dimensional matrix, a connected domain is calculated, a smaller connected domain is removed, a skeleton is extracted by using a coronary artery skeleton extraction algorithm, and a keel node index is established. The keel nodes are discrete points of the central line. The keel node index is the relationship between a child node and a father node;

specifically, firstly, converting a dot matrix cloud into a binary high-dimensional matrix, calculating a connected domain, and rejecting a smaller connected domain, wherein the connected domain with less than 100 pixel points is generally rejected;

secondly, extracting bones by using a coronary artery bone extraction algorithm, marking the physical coordinate positions of keel nodes, and recording the positions in the first three columns in a matrix A, wherein the total number of the keel nodes is N, and the spatial position of the ith node is p_i＝(x_i,y_i,z_i) And (4) showing. Calculating the equivalent area A of coronary artery on each node_iEquivalent diameter d_iDirection of blood flow v_i(first derivative of spatial position) and the like. Equivalent area refers to the area enclosed by a perpendicular section to the coronary arteries; the equivalent diameter is calculated by the formula

Calculating the blood flow direction according to respective mathematical definition, adding all data into the matrix A according to the keel coordinate position, and directly calling the subsequent calculation;

finally, find node i in the reverse direction of blood flow-v_iThe point which is closest to the node is taken as a father node, the current node is called as a child node, the blood flow direction is from the father node to the child node, and the nodeI.e. the discrete points that constitute the centerline of the coronary artery branch. It should be noted that: the blood flow entry point has no parent node, the blood flow exit point has no child node, and the bifurcation point is a parent node of the plurality of child nodes. And searching a branch path from the inlet to the outlet according to the spatial relationship between the child node and the parent node, namely searching the parent node of each node from the outlet until the inlet node of the coronary artery. The coronary artery keel nodes traverse sequentially from the entrance to the first-level branch, the second-level branch and the like until all the exits, so that the program searches all the exits from the coronary artery entrance to obtain a coronary artery branch hierarchical relation graph shown in fig. 5, namely keel indexes. The outlet of the coronary artery can be preset, for example, the position of the tail end of a coronary artery branch with the diameter of 1-2 mm is set as the outlet of the coronary artery; wherein the bifurcation is the intersection of the coronary branches.

In practical application, the spatial position relationship of the coronary artery branches can be established according to the arrangement of the coronary artery branches and the preset sequence, and the coronary artery branches are named according to the preset naming rule; thus, the coronary artery branches are mathematically and geometrically graded and named from top to bottom and from left to right, and the problem that the flow at the tail end of the coronary artery cannot be regularly and programmatically evaluated before FFRCT calculation is solved;

specifically, according to the above-mentioned coronary artery keel node index relationship, a coronary artery branch bifurcation point is found, and the sequence of traversing the sub-nodes of the coronary artery branch bifurcation point along the coronary artery from top to bottom and from left to right along the heart center is determined;

based on the keel data matrix A, from a keel node at the entrance of a coronary artery, namely from a discrete point where the aorta and the coronary artery intersect, traversing the keel node to a first bifurcation point according to the index relation of the keel node of the coronary artery, acquiring and recording the sequence of sub-nodes of the first bifurcation point, and storing the sequence in the matrix B. Taking the first bifurcation point containing two child nodes as an example, according to the relationship that the child nodes of the bifurcation point all share one father node, the direction vector Dir _ fast pointing to the father node of the bifurcation point and the direction vector Dir _ son pointing to two first-level child nodes B (1) and B (2) of the bifurcation point are calculated₁，Dir_son₂Since the distance between the keel node and the point is about one pixel (the distance between two pixel points is about 0.3mm), the three vectors can be regarded as being in the same plane. According to the right-hand rule, normal vectors of direction vectors of a bifurcation point pointing to a father node of the bifurcation point and direction vectors of the bifurcation point pointing to two first-level child nodes are respectively calculated and can be respectively expressed by expressions (1) and (2);

positioning the heart Center according to the distribution of the left and right coronary arteries, calculating a direction vector Dir _ Center of a bifurcation point pointing to the sphere Center by taking the coronary artery Center as the sphere Center, and judging the storage positions of the two sub-nodes in the matrix B by calculating dot products a and B of the normal vector and the direction vector of the bifurcation point pointing to the sphere Center; a and b may be represented by expressions (3) and (4), respectively;

when a is less than 0 and less than B, the positions of elements in the matrix B are kept unchanged, and as shown in FIG. 6a, two keel nodes are distributed in a left-right mode;

when B is less than 0 and less than a, the positions of elements in the matrix B are interchanged, and as shown in figure 6a, the two keel nodes are in a left distribution type;

when a is greater than 0 and b is greater than 0, calculating the Dir _ fast and Dir _ son₁And Dir _ son₂The included angles are respectively expressed by expressions (5) and (6);

if theta is greater than theta₁＞θ₂The positions of the elements in the matrix B remain unchanged; instead, interchanging the element positions in matrix B, as shown in fig. 6B, the two coronary branches are left-distributed;

when a is less than 0 and b is less than 0, the vector Dir _ fast and the vector Dir _ son are calculated₁And Dir _ son₂Included angle theta₁,θ₂: if theta is greater than theta₁＞θ₂Interchanging the element positions in the matrix B; in contrast, the positions of the elements in the matrix B remain unchanged, as shown in fig. 6c, and the two keel nodes are in a right distribution type;

according to the rule, after the positions of the elements in the matrix B are changed, all the remaining bifurcation points are sequentially traversed until all the outlets of the coronary artery are traversed, so that the traversing sequence of the coronary artery branches from top to bottom and from left to right is determined.

Further, the coronary artery branches may be named based on their spatial position order;

the coronary artery trunk is named C according to the traversal order specified for the coronary artery branches above_mThe other branches of the coronary artery are named according to a certain rule in the left-right order of the determined branches of the coronary artery, and can be represented by expression (7);

where m is the naming attribute of the last branch, n-1 denotes the left branch, n-2 denotes the right branch, and all keels that thus circulate to all coronary branches are named, as shown in fig. 7;

first, the coronary artery entrance keel node is named as attribute C₀When the number of the keel nodes is 0, sequentially traversing all the rest keel nodes of the main trunk, and sequentially inheriting the naming attribute of the father node of each keel node;

secondly, when the keel traverses from the main trunk to the first bifurcation point, the left branch L of the first bifurcation point is appointed according to the determined traversal sequence of the coronary artery branches from top to bottom and from left to right₀₁The first keel node grade is C₀₁＝C₀X 10+1 ═ 1, right branch R₀₂The first keel joint is named as C₀₂＝C₀X 10+2 ═ 2. All the rest keel nodes of the branch inherit the name attribute of the father node of the branch in sequence;

finally, when branch L is traversed subsequently₀₁When a bifurcation point is encountered, according to the traversal sequence of the bifurcation point of the coronary artery branches based on the left to the right of the heart, a left branch under the bifurcation point is designated as C₀₁₁＝C₀₁X 10+1 ═ 11, right branch rating C₀₁₂＝C₀₁X 10+2 ═ 12; likewise, branch R₀₂Branches after the rear bifurcation point are all according to branch L₀₁The cases are named, namely C₀₂₁＝C₀₂×10+1＝21，C₀₂₂＝C₀₂X 10+2 ═ 22, this loop continues until the entire coronary keel node is traversed, completing the named coronary branch as shown in fig. 7.

Step 102: determining the blood flow volume of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of each coronary artery branch corresponding to the discrete point at the root intersection position of each central line;

here, the total blood volume of the coronary artery may be assigned to each coronary artery branch according to a preset assignment rule. The preset allocation rule can be determined according to the blood allocation relation of the parent coronary artery branch and the child coronary artery branch;

furthermore, the mass of the left ventricular myocardium can be calculated from the myocardium of the patient obtained by organ separation, and the blood flow of the whole coronary artery can be expressed by expression (8) according to the law of the different growth rate between the coronary blood flow and the myocardial mass;

wherein Q is_corIs the total coronary blood flow; q₀A constant coefficient, which can be taken as 5.4; m_myoLeft ventricular myocardial mass;

the profile of the coronary artery includes: left dominant, balanced, and right dominant; determining the blood flow Q of the left coronary artery from the total blood flow of the whole coronary artery_{cor_left}Blood flow Q to the right coronary artery_{cor_right}The ratio of the two is respectively 8: 2. 7.5: 2.5 and 7: 3. for example, if the coronary artery profile is the right dominant profile, then the coronary left and right branch flow distribution is: q_{cor_left}＝70％Q_cor，Q_{cor_right}＝30％Q_cor；

In combination with the poisson law, the blood flow in a coronary artery branch is proportional to the third power of the corresponding branch diameter, and can be expressed by expression (9);

wherein Q is the intravascular flow, d is the diameter of the blood vessel, mu is the hemodynamic viscosity coefficient, and lambda is a proportionality constant representing the energy consumed by the metabolism of the blood vessel per unit volume;

determining respective blood flow volumes of a left coronary artery branch and a right coronary artery branch according to the proportion of preset left coronary artery blood flow volume and preset right coronary artery blood flow volume in total blood flow volumes of coronary arteries;

the blood flow of each coronary branch is expressed by expression (10);

wherein d is_mnRepresenting the diameters, Q, of the sub-coronary branches belonging to the same parent coronary branch at the root node position of the discrete point of the respective corresponding centerline_mRepresenting the total blood flow of the parent coronary artery branch, m representing the parent coronary artery branch, n representing different child coronary artery branches of the m parent coronary artery branches;

taking the bifurcation of the main coronary artery into two sub-coronary artery branches as an example, d₀Is the diameter of the main coronary artery, d₀₁And d₀₂The diameters of the coronary artery branches corresponding to the two primary sub-nodes under the first bifurcation point respectively;

calculating the total blood flow of left (right) coronary artery according to the distribution pattern of coronary artery branches, i.e. main trunk l_mBlood flow volume Q_m(m ═ 0). The other branch flow of the coronary artery is distributed according to the left and right branch flow of the judged coronary artery according to a certain rule under one bifurcation, and the flow volume of the two sub-coronary artery branches can be expressed by an expression (11);

wherein, m is the naming attribute of the last branch, n-1 represents the left branch, n-2 represents the right branch, and the flow is circulated to all the coronary artery branches;

according to the classification of coronary artery branches and the distribution rule of coronary artery blood flow from top to bottom, the coronary artery branch diameters of the second nodes of the left branch and the right branch under the first bifurcation point are respectively obtained, and the branch l is obtained by calculation₀₁And l₀₂The blood flow volume of (c) can be expressed by expressions (12) and (13), respectively;

branch l₀₁Bifurcating to obtain branch l₀₁₁And l₀₁₂According to the same distribution rule, calculating to obtain branch l₀₁₁And l₀₁₂The blood flow volume of (c) can be represented by expressions (14) and (15), respectively;

likewise, branch l₀₂Bifurcating to obtain branch l₀₂₁And l₀₂₂According to the same distribution rule, calculating to obtain branch l₀₂₁And l₀₂₂Blood ofThe flow rates can be expressed by expressions (16) and (17), respectively;

if branch l₀₁₁、l₀₁₂、l₀₂₁And l₀₂₂If there is a further bifurcation, the blood flow of the next branch is distributed step by step according to the diameter of the bifurcation according to the above coronary artery grading principle, and the circulation is continued until the bifurcation does not exist in the branch, namely the outlet of the branch is the outlet of the coronary artery branch, and the blood flow corresponding to the branch is the blood flow of the outlet of the coronary artery branch.

Further, a preset fitting rule is adopted to perform linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line to obtain a first diameter fitting curve; when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule;

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value; performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve; and when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule. (ii) a

Here, the discrete point at the intersection position of the centerline root is a discrete point at the intersection position of the parent coronary artery branch and the child coronary artery branch and at the intersection position of the child coronary artery branch.

Specifically, the comparison of the coronary artery branch center line extracted from the three-dimensional coronary artery point cloud, that is, the coronary artery branch keel and the original three-dimensional coronary artery point cloud, shows that the diameter obtained may be inaccurate due to the fact that the calculation difficulty is large, and the extracted equivalent diameter is smaller than the real coronary artery branch diameter due to the fact that the concentration of the contrast agent at the tail end of the outlet branch is reduced. In addition, it was found from the three-dimensional coronary artery model reconstructed from the CTA image that stenosis may occur in the coronary artery branches at the bifurcation root. If the diameter of the bifurcation is directly taken to distribute the flow of the coronary artery, a large error may be generated, which causes inaccurate calculation of the microcirculation resistance at the tail end of the coronary artery branch, and further causes inaccurate calculation of the FFR. The method can be used for repairing the stenosis condition at the crossing position by determining the position of the coronary artery branch stenosis;

therefore, preferably, before the linear fitting can be performed on the coronary branch diameter corresponding to each discrete point on the central line of the coronary branch, the method further includes: according to a preset elimination rule, eliminating discrete points with preset lengths of coronary artery branches; the preset elimination rule can be set according to the actual condition of the coronary artery model, and the intersection points and/or the tail ends of the coronary artery branches are eliminated; the preset length can be set according to the abnormal condition of the coronary artery branch, such as 1mm or 2 mm;

specifically, abnormal points at the head and the tail of the coronary artery branch are removed. Comparing the keel nodes at the bifurcation with the bifurcation areas of the real coronary branches, the finding that the main trunk of the coronary branch has about 1mm keel nodes, and the bifurcation branches have about 2mm keel nodes in the bifurcation triangular areas is that the real coronary branch bifurcations are connected with the main trunk of the coronary branch. To coronary artery branch trunk, reject the fossil fragments node in the terminal 1mm, to inside branch, the fossil fragments node in 2mm and 1mm is rejected respectively to the head and the tail, to export branch, reject equally the fossil fragments node in head and the tail 2mm and 1mm, as new branch fossil fragments node.

Further, performing EMD on the coronary artery branch diameter with the length larger than the preset branch length, removing the mode with the maximum fluctuation when the EMD result is larger than the preset mode, and adding the residual mode data to determine the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch;

specifically, the equivalent diameter of the coronary branch keel node is filtered. For coronary arteries with longer branches, i.e. longer than a predetermined branch lengthPerforming EMD on equivalent diameters of different coronary artery branches by using an EMD method, decomposing to generate different modes, keeping the diameters of the branches unchanged for the coronary artery branches less than or equal to the two modes, and marking the Diameter sequence as Diameter_emd(ii) a Otherwise, removing the mode with the maximum fluctuation, and adding the residual mode data to obtain a new coronary artery branch keel Diameter sequence Diameter_emd(ii) a Wherein, 20 keel nodes are taken according to the preset branch length. For coronary artery branches with keel nodes less than or equal to 20 nodes, filtering is not carried out, and Diameter sequences are recorded_emd；

Here, the performing linear fitting on the coronary artery branch diameter corresponding to each discrete point by using the preset fitting rule includes: linearly fitting the diameters of the coronary artery branches corresponding to each discrete point, and expressing a curve obtained by fitting by using the following expression: the first and second diameter-fitted curves may be fitted using the same fitting method; the first diameter fitting curve and the second diameter fitting curve can adopt fitting expressions in the same form;

in general, for normal coronary branches, the diameter from the bifurcation to the end is a decreasing series, i.e., the slope of the fitting function is less than 0; firstly, the Diameter distribution of coronary artery branches of different branches can be fitted to obtain a first Diameter fitting curve Diameter_1polyfitThe fitted functions are linear functions and can be represented by expression (18);

wherein, Distance_emdRepresenting the bit order, p, of each discrete point on the central line₁(1) As the slope of the fitted function, p₁(2) Representing the intercept of the fitting function, p₁(1) And p₁(2) Are each p₁＝polyfit(Distance_emd,Diameter_emd1) two constants obtained by fitting, Diameter_emdThe sequence of coronary branch diameters corresponding to each discrete point is represented. The polyfit () represents a fitting function;

when the slope p of the fitting function₁(1) At > 0, it can be preliminarily determined that coronary branches are crossing as shown in FIG. 8Repairing the diameter of the coronary artery branch corresponding to the discrete point at the intersection position of the root part of the central line according to a preset repairing rule when the fork is in a narrow state; the set repairing rule can be determined according to the diameter distribution of coronary artery branches, and the diameters corresponding to the discrete points at the intersection positions can be repaired by adopting the diameters of the adjacent discrete points.

Further, the coronary artery branch diameter corresponding to the discrete point at the central line root intersection position can be determined by adopting an expression (19);

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe method comprises the steps of representing the coronary artery branch diameter corresponding to the last discrete point at the tail end of the central line of the same coronary artery branch, representing the position of the last discrete point by n, and representing the coronary artery branch diameter difference of preset adjacent discrete points by gamma. When the interval of the discrete points is set to be 0.25 mm-0.75 mm, the value range of gamma can be set to be 0.0005 mm-0.0015 mm, and when the interval of the discrete points is 0.5mm, the value range of gamma is 0.001 mm;

when the slope p of the fitting function₁(1) When the number is less than 0, the situation that the coronary artery branches are not narrowed at the intersection can be preliminarily determined, and the repair is not needed; however, it cannot be excluded that there is a wide stenosis in the middle of the coronary branches, and that the slope p of the function is such that a stenosis occurs in the middle of the coronary branches₁(1) Less than 0 may also occur; in order to eliminate the influence of the diameter of the stenosis position on the fitting function, the first-time fitting function can be used for calculating the stenosis rate of the current coronary artery branch;

can utilize Diameter_1polyfitAnd Diameter_emdIs divided by Diameter_1polyfitAs the first diameter-fitted curve stenosis rate at the coronary artery branch stenosis, the first diameter-fitted curve stenosis rate can be expressed by expression (20);

due to the function slope p₁(1) < 0, it is possible to preliminarily locate the position where the coronary artery branch stenosis occurs not to occur at the root of the bifurcation. For branches without stenosis or with a low degree of stenosis, the fitted keel diameter function can be regarded as the diameter of an ideal coronary artery branchDistribution, whereas for coronary branches with a severe stenosis in the middle, the fitting function is not very close to the true coronary branch diameter distribution due to the presence of the stenosis. Therefore, discrete points with stenosis rate larger than a first preset stenosis rate threshold value, such as 50%, can be eliminated to obtain a new Diameter coronary artery branch Diameter sequence Diameter_newFitting the diameters of the coronary artery branches after the discrete points are removed by adopting a fitting method of fitting the same first Diameter fitting curve to obtain a second Diameter fitting curve Diameter_2polyfitCombined with Diameter_newAnd Distance_newFitting to obtain Diameter_2polyfitAnd can be represented by expression (21);

wherein p is₂(1) As the slope of the fitted function, p₂(2) Representing the intercept of the fitting function, p₂(1) And p₂(2) Are each p₂＝polyfit(Distance_new,Diameter_new1) two constants obtained by fitting, Distance_newRepresents the bit order sequence for each discrete point on the centerline, i.e., the bit order sequence for each discrete point on the centerline. The polyfit () represents a fitting function; here, expressions (18) and (21) are the same calculation method except that the variables are different.

Reuse of Diamete_2polyfitAnd Diameter_newIs divided by diameter_2polyfitThe stenosis rate of the second diameter-fitted curve as a coronary artery branch can be expressed by expression (22);

here, the stenosis rate of the first diameter-fitted curve and the stenosis rate of the second diameter-fitted curve respectively represent the stenosis rates of the coronary artery branches before and after passing through the discrete point where the rejection stenosis rate is greater than the first preset stenosis rate threshold. After two fits, for the stenosis rate at the intersection position, if it is greater than a second preset stenosis rate threshold, it is determined that stenosis has occurred. According to a preset repairing rule, repairing the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root of the central line; the repairing method is consistent with the method for determining the coronary artery branch diameter corresponding to the discrete point at the intersection position of the root part of the central line by adopting the expression (19), and the details are not repeated.

Therefore, the coronary artery branch with stenosis at the root of the coronary artery branch is repaired to obtain the new equivalent diameter of the bifurcation, and the blood flow of the coronary artery branch is directly distributed according to the repair, so that the accuracy of the flow distribution of the coronary artery branch is improved.

Furthermore, the stenosis of the coronary artery branch can be marked for the reference of the medical staff. Here, the stenosis rate maximum values corresponding to different coronary artery branches may be searched, and it is generally clinically concerned that the main coronary artery branches have a stenosis rate higher than a certain threshold, for example, 50%, and therefore, the maximum value having a stenosis rate smaller than the threshold is removed from the maximum values of the coronary artery branches, for the maximum value having a stenosis rate larger than the threshold, the maximum value coordinate is obtained and positioned on the coronary artery branch keel, the coronary artery branch keel nodes are searched forward and backward from the stenosis coordinate point, respectively, until the corresponding stenosis rate is smaller than or equal to a certain value, for example, 10%, the coronary artery branch keel node farthest from the stenosis point forward and backward is marked and recorded, and the distance of the keel nodes at both ends along the keel direction is calculated as the stenosis length StenosisLength. Stenosis information can be provided to medical personnel for reference.

Step 103, determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet according to the blood flow of each coronary artery branch;

here, the resistance of the downstream coronary branch microcirculation corresponding to different branch outlets of the normal coronary artery in the resting state is calculated by combining the relationship among the pressure, the blood flow and the vascular resistance in the resting state of the coronary artery. The preset blood outlet can be determined according to the diameter of the tail end of the coronary artery branch, the diameter of the blood outlet can be preset, the tail end of the coronary artery branch is smaller than the diameter of the preset blood outlet, and the coronary artery branch is determined to be the coronary artery branch corresponding to the preset blood outlet. The diameter of the preset blood outlet can be 1-2 mm.

Preferably, the mean aortic pressure is subtracted from the epicardial coronary pressure drop, and then the central venous pressure is subtracted to obtain the pressure difference from the end of the coronary artery branch to the end of the vein; dividing the coronary artery pressure by the blood flow of the coronary artery branch corresponding to the preset blood outlet to determine that the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet is in a resting state

Specifically, under the condition that an epicardial blood vessel is not narrowed, the epicardial coronary artery pressure drop of a normal person is clinically measured to be 1-2 mmHg, 1mmHg can be taken, and the coronary artery inlet pressure is taken as the mean aortic pressure P_a90mmHg, distal pressure of coronary microcirculation, i.e. central venous pressure P_d6.25mmHg, the pressure difference Δ P from the end of the coronary branch to the end of the vein is thus equal to ((P)_a-1)-P_d) 82.75 mmHg. According to Δ P ═ Q × R_rQ is the blood flow of the coronary artery branch corresponding to the preset blood outlet, and the microcirculation resistance of the tail end of each branch is ensured under the resting state

Finally, obtaining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in the hyperemia state according to the proportion coefficient of the microcirculation resistance of the coronary artery branch in the preset rest state and the microcirculation resistance of the coronary artery branch in the hyperemia state; calculating the microcirculation resistance R of the branch end of the coronary artery in a hyperemia state according to a preset proportionality coefficient such as 0.24_h＝0.24R_r. Thus, the calculation of the microcirculation resistance at the end of each branch coronary artery is completed.

Based on this method, the classification and resistance display of the real coronary branches is shown in fig. 8, and the coronary FFR distribution is obtained by CFD calculation.

Fig. 10 shows a table of FFR calculation results of the left coronary branch obtained by performing FFR calculation with respect to the naming and resistance maps of the real coronary keel points shown in fig. 9. The FFR calculation results of the left and right coronary branches obtained by performing the FFR calculation with respect to the naming and resistance maps of the real coronary keel points after the diameter of the cross-site discrete points is restored in fig. 11 are shown in fig. 12.

Therefore, the flow of each branch of the coronary artery is accurately calculated according to the diameter of the root of the branch at the bifurcation of the coronary artery by a step-by-step distribution method, the accurate resistance of each outlet of each branch of the coronary artery is obtained, and the accuracy of the calculation result of the FFRCT technology is improved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (12)

1. A device for determining the resistance of the microcirculation of the coronary arteries, characterized in that it comprises: a model processing module, a modification module, a first determination module, and a second determination module, wherein,

the model processing module is used for establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch according to the three-dimensional image model of the coronary artery; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

the correction module is used for determining the stenosis position of the coronary artery branch corresponding to the discrete point of the root intersection position of each central line and repairing the diameter of the coronary artery branch at the stenosis position;

the first determining module is used for determining the blood flow of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of the repaired coronary artery branch;

the second determining module is used for determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a resting state by dividing the pressure difference from the tail end of the coronary artery branch to the tail end of the vein by the blood flow of the coronary artery branch corresponding to the preset blood outlet;

the second determination module is further used for determining the microcirculation resistance of the coronary artery branch in the hyperemia state according to the microcirculation resistance of the branch end corresponding to the preset blood outlet in the rest state; wherein the microcirculation resistance of the coronary branches at said hyperemic state is used to calculate the coronary fractional flow reserve FFR.

2. The apparatus of claim 1, wherein the model processing module is specifically configured to:

determining the hierarchical relationship of coronary artery branches according to the cross-connection relationship of discrete points of each coronary artery branch central line and the preset blood flow direction;

the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch;

the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch.

3. The apparatus of claim 1, wherein the first determining module is specifically configured to:

the total coronary blood flow is calculated according to the law of the anisotropic growth between coronary blood flow and myocardial mass using the following expression:

Q_cor＝Q₀M_myo ^0.75

wherein Q is_corRepresenting total coronary blood flow; q₀Denotes a predetermined coefficient, M_myoRepresenting left ventricular myocardial mass;

determining respective blood flow volumes of the left coronary artery and the right coronary artery according to preset distribution ratios of the blood flow volumes of the left coronary artery and the right coronary artery in total blood flow volumes of the coronary arteries;

the blood flow of each coronary branch is expressed in terms of:

wherein d is_m1、d_m2、……、d_mnThe diameter of the sub-coronary artery branches belonging to the same father coronary artery branch at the root node position of the discrete point of the corresponding central line, m is the naming attribute of the father coronary artery branch, n is the sub-coronary artery branch of the same father coronary artery branch, n is an integer greater than or equal to 1, and Q_mRepresenting the total blood flow of the parent coronary branch.

4. The apparatus of claim 3, wherein the second determining module is specifically configured to:

subtracting the difference between the epicardial coronary artery pressure drop and the central venous pressure from the average aortic pressure to obtain the pressure difference from the branch end of the coronary artery to the vein end; the expression is Δ P ═ P ((P)_a-1)-P_d) (ii) a Wherein, P_aIs the mean aortic pressure, P_dThe central venous pressure is obtained, the constant 1 is the epicardial coronary artery pressure drop of a normal person obtained by clinical measurement, and the delta P is the pressure difference from the tail end of a coronary artery branch to the tail end of a vein; correspondingly, the expression of the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet is

Wherein R is_rThe resistance of microcirculation at the tail end of the branch corresponding to the preset blood outlet in a resting state, and Q is the blood flow of the coronary artery branch corresponding to the preset blood outlet.

5. The apparatus of claim 1, wherein the modification module is specifically configured to:

performing linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a first diameter fitting curve;

and when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule.

6. The apparatus of claim 5, wherein the correction module is further configured to:

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value;

performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve;

and when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule.

7. The apparatus of claim 6, wherein the modification module is specifically configured to:

linearly fitting the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line, and expressing a first diameter fitting curve obtained by fitting by adopting the following expression:

Diameter_polyfit＝p(1)·Distance_emd+p(2)

wherein, Distance_emdRepresenting the bitwise sequence of each discrete point on the centerline, p (1) representing the slope of the fit function of the first diameter fit curve, and p (2) representing the fit function intercept of the first diameter fit curve;

linearly fitting the diameters of the coronary artery branches corresponding to the remaining discrete points, and expressing a fitted second diameter fitting curve obtained by fitting by using the following expression:

Diamete_2polyfit＝p₂(1)·Distance_new+p₂(2)

wherein, Distance_newBit order sequence, p, representing each discrete point remaining on the central line₂(1) Slope of the fitting function, p, representing the fitted curve of the second diameter₂(2) The fitting function intercept of the second diameter fitting curve is represented.

8. The apparatus according to claim 5 or 6, wherein the modification module is specifically configured to:

determining the diameters of the coronary artery branches corresponding to the discrete points at the root intersection positions of the central lines by adopting the following expression:

d₁＝d_n+(n-1)γ

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nThe diameter of the coronary artery branch corresponding to the last discrete point at the tail end of the central line is represented, n represents the bit number of the discrete point, and gamma represents the diameter difference of the coronary artery branch of the preset adjacent discrete points.

9. The apparatus of claim 5 or 6, wherein the modification module is further configured to:

and according to a preset rejection rule, rejecting discrete points with preset length of coronary artery branches.

10. The apparatus of claim 5 or 6, wherein the modification module is further configured to:

performing Empirical Mode Decomposition (EMD) on the branch diameter of the coronary artery with the length larger than the preset branch length;

and when the EMD result is larger than the preset mode, removing the mode with the maximum fluctuation, adding the residual mode data, and determining the residual mode data as the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch.

11. A storage medium having an executable program stored thereon, the executable program when executed by a processor implementing:

according to the three-dimensional image model of the coronary artery, establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

determining the stenosis position of the coronary artery branch corresponding to the discrete point of the root intersection position of each central line, and repairing the diameter of the coronary artery branch at the stenosis position;

determining the blood flow of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of the repaired coronary artery branch;

dividing the quotient of the pressure difference from the tail end of the coronary artery branch to the tail end of the vein by the blood flow of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a resting state;

determining the microcirculation resistance of coronary artery branches in a hyperemia state according to the microcirculation resistance of the tail ends of the branches corresponding to the preset blood outlets in the rest state; wherein the microcirculation resistance of the coronary branches at the hyperemic state is used to calculate the coronary fractional flow reserve, FFR;

wherein the determining the hierarchical relationship of each coronary artery branch according to the connection relationship of each central line comprises:

determining the hierarchical relationship of coronary artery branches according to the cross-connection relationship of discrete points of each coronary artery branch central line and the preset blood flow direction;

the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch;

the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch;

wherein the determining the blood flow of each coronary artery branch by adopting a preset distribution rule comprises:

the total coronary blood flow is calculated according to the law of the anisotropic growth between coronary blood flow and myocardial mass using the following expression:

Q_cor＝Q₀M_myo ^0.75

wherein Q is_corRepresenting total coronary blood flow; q₀Denotes a predetermined coefficient, M_myoRepresenting left ventricular myocardial mass;

determining respective blood flow volumes of the left coronary artery and the right coronary artery according to preset distribution ratios of the blood flow volumes of the left coronary artery and the right coronary artery in total blood flow volumes of the coronary arteries;

the blood flow of each coronary branch is expressed in terms of:

wherein d is_m1、d_m2、……、d_mnThe diameter of the sub-coronary artery branches belonging to the same father coronary artery branch at the root node position of the discrete point of the corresponding central line, m is the naming attribute of the father coronary artery branch, n is the sub-coronary artery branch of the same father coronary artery branch, n is an integer greater than or equal to 1, and Q_mRepresenting the total blood flow of the parent coronary artery branch;

wherein, according to the blood flow of each coronary artery branch, determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet comprises the following steps:

subtracting the difference between the epicardial coronary artery pressure drop and the central venous pressure from the average aortic pressure to obtain the pressure difference from the branch end of the coronary artery to the vein end; the expression is Δ P ═ P ((P)_a-1)-P_d) (ii) a Wherein, P_aIs the mean aortic pressure, P_dThe central venous pressure is obtained, the constant 1 is the epicardial coronary artery pressure drop of a normal person obtained by clinical measurement, and the delta P is the pressure difference from the tail end of a coronary artery branch to the tail end of a vein;

correspondingly, the expression of the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet is

Wherein R is_rThe resistance of microcirculation at the tail end of the branch corresponding to the preset blood outlet in a resting state is shown, and Q is the blood flow of the coronary artery branch corresponding to the preset blood outlet;

the executable program when executed by the processor further implements:

performing linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a first diameter fitting curve;

when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule;

the executable program when executed by the processor further implements:

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value;

performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve;

when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, according to a preset repair rule, performing repair treatment on the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line;

wherein, the adoption is predetermine the fitting rule, carries out linear fitting to the coronary artery branch diameter that each discrete point corresponds, includes:

linearly fitting the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line, and expressing a first diameter fitting curve obtained by fitting by adopting the following expression:

Diameter_polyfit＝p(1)·Distance_emd+p(2)

wherein, Distance_emdRepresenting the bitwise sequence of each discrete point on the centerline, p (1) representing the slope of the fit function of the first diameter fit curve, and p (2) representing the fit function intercept of the first diameter fit curve;

linearly fitting the diameters of the coronary artery branches corresponding to the remaining discrete points, and expressing a fitted second diameter fitting curve obtained by fitting by using the following expression:

Diamete_2polyfit＝p₂(1)·Distance_new+p₂(2)

wherein, Distance_newBit order sequence, p, representing each discrete point remaining on the central line₂(1) Slope of the fitting function, p, representing the fitted curve of the second diameter₂(2) A fitting function intercept representing a second diameter fitting curve;

according to a preset repairing rule, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line, wherein the repairing comprises the following steps:

determining the diameters of the coronary artery branches corresponding to the discrete points at the root intersection positions of the central lines by adopting the following expression:

d₁＝d_n+(n-1)γ

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nRepresenting the coronary artery branch diameter corresponding to the last discrete point at the tail end of the central line, n representing the position of the discrete point, and gamma representing the coronary artery branch diameter difference of preset adjacent discrete points;

before the first diameter fitting curve is fitted, discrete points of the preset length of the coronary artery branches are removed according to a preset removing rule;

before linear fitting is carried out on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line, Empirical Mode Decomposition (EMD) is carried out on the coronary artery branch diameter with the length larger than the preset branch length;

and when the EMD result is larger than the preset mode, removing the mode with the maximum fluctuation, adding the residual mode data, and determining the residual mode data as the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch.

12. An apparatus for determining coronary arterial microcirculation resistance, comprising a processor, a memory and an executable program stored on the memory and capable of being executed by the processor, wherein the processor executes the executable program to perform:

according to the three-dimensional image model of the coronary artery, establishing a central line which is formed by discrete points and respectively corresponds to each coronary artery branch; determining the hierarchical relation of each coronary artery branch according to the connection relation of each central line;

determining the stenosis position of the coronary artery branch corresponding to the discrete point of the root intersection position of each central line, and repairing the diameter of the coronary artery branch at the stenosis position;

determining the blood flow of each coronary artery branch by adopting a preset distribution rule according to the hierarchical relation of each coronary artery branch and the diameter of the repaired coronary artery branch;

dividing the quotient of the pressure difference from the tail end of the coronary artery branch to the tail end of the vein by the blood flow of the coronary artery branch corresponding to the preset blood outlet to determine the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet in a resting state;

determining the microcirculation resistance of coronary artery branches in a hyperemia state according to the microcirculation resistance of the tail ends of the branches corresponding to the preset blood outlets in the rest state; wherein the microcirculation resistance of the coronary branches at the hyperemic state is used to calculate the coronary fractional flow reserve, FFR;

wherein the determining the hierarchical relationship of each coronary artery branch according to the connection relationship of each central line comprises:

determining the hierarchical relationship of coronary artery branches according to the cross-connection relationship of discrete points of each coronary artery branch central line and the preset blood flow direction;

the coronary branch hierarchy comprises a parent coronary branch and a child coronary branch;

the preset blood flow direction flows from the parent coronary artery branch to the child coronary artery branch;

wherein the determining the blood flow of each coronary artery branch by adopting a preset distribution rule comprises:

the total coronary blood flow is calculated according to the law of the anisotropic growth between coronary blood flow and myocardial mass using the following expression:

Q_cor＝Q₀M_myo ^0.75

wherein Q is_corRepresenting total coronary blood flow; q₀Denotes a predetermined coefficient, M_myoRepresenting left ventricular myocardial mass;

determining respective blood flow volumes of the left coronary artery and the right coronary artery according to preset distribution ratios of the blood flow volumes of the left coronary artery and the right coronary artery in total blood flow volumes of the coronary arteries;

the blood flow of each coronary branch is expressed in terms of:

wherein d is_m1、d_m2、……、d_mnThe diameter of the sub-coronary artery branches belonging to the same father coronary artery branch at the root node position of the discrete point of the corresponding central line, m is the naming attribute of the father coronary artery branch, n is the sub-coronary artery branch of the same father coronary artery branch, n is an integer greater than or equal to 1, and Q_mRepresenting the total blood flow of the parent coronary artery branch;

wherein, according to the blood flow of each coronary artery branch, determining the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet comprises the following steps:

subtracting the difference between the epicardial coronary artery pressure drop and the central venous pressure from the average aortic pressure to obtain the pressure difference from the branch end of the coronary artery to the vein end; the expression is Δ P ═ P ((P)_a-1)-P_d) (ii) a Wherein, P_aIs the mean aortic pressure, P_dThe central venous pressure is obtained, the constant 1 is the epicardial coronary artery pressure drop of a normal person obtained by clinical measurement, and the delta P is the pressure difference from the tail end of a coronary artery branch to the tail end of a vein;

correspondingly, the expression of the microcirculation resistance of the coronary artery branch corresponding to the preset blood outlet is

Wherein R is_rIs the microcirculation resistance of the branch end corresponding to the preset blood outlet in a resting state,q is the blood flow of the coronary artery branch corresponding to the preset blood outlet;

the executable program when executed by the processor further implements:

performing linear fitting on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a first diameter fitting curve;

when the slope of the fitting function of the first diameter fitting curve is greater than 0, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line according to a preset repairing rule;

the executable program when executed by the processor further implements:

when the slope of the fitting function of the first diameter fitting curve is smaller than 0, calculating the stenosis rate of the first diameter fitting curve, and eliminating discrete points with the stenosis rate higher than a first preset stenosis rate threshold value;

performing linear fitting on the coronary artery branch diameter corresponding to each remaining discrete point on the coronary artery branch central line by adopting a preset fitting rule to obtain a second diameter fitting curve, and calculating the stenosis rate of the second diameter fitting curve;

when the stenosis rate corresponding to the discrete point at the root intersection position of the central line is higher than a second preset stenosis rate threshold value, according to a preset repair rule, performing repair treatment on the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line;

wherein, the adoption is predetermine the fitting rule, carries out linear fitting to the coronary artery branch diameter that each discrete point corresponds, includes:

linearly fitting the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line, and expressing a first diameter fitting curve obtained by fitting by adopting the following expression:

Diameter_polyfit＝p(1)·Distance_emd+p(2)

wherein, Distance_emdRepresenting the sequence of bits for each discrete point on the centerline, p (1) representing the slope of the fit function for the first diameter fit curve, and p (2) representing the first diameterFitting function intercept of the fitting curve;

linearly fitting the diameters of the coronary artery branches corresponding to the remaining discrete points, and expressing a fitted second diameter fitting curve obtained by fitting by using the following expression:

Diamete_2polyfit＝p₂(1)·Distance_new+p₂(2)

wherein, Distance_newBit order sequence, p, representing each discrete point remaining on the central line₂(1) Slope of the fitting function, p, representing the fitted curve of the second diameter₂(2) A fitting function intercept representing a second diameter fitting curve;

according to a preset repairing rule, repairing the coronary artery branch diameter corresponding to the discrete point at the root intersection position of the central line, wherein the repairing comprises the following steps:

determining the diameters of the coronary artery branches corresponding to the discrete points at the root intersection positions of the central lines by adopting the following expression:

d₁＝d_n+(n-1)γ

wherein d is₁Representing the diameter of the coronary branch at discrete points corresponding to the intersection of the root of the centerline, d_nRepresenting the coronary artery branch diameter corresponding to the last discrete point at the tail end of the central line, n representing the position of the discrete point, and gamma representing the coronary artery branch diameter difference of preset adjacent discrete points;

before the first diameter fitting curve is fitted, discrete points of the preset length of the coronary artery branches are removed according to a preset removing rule;

before linear fitting is carried out on the coronary artery branch diameter corresponding to each discrete point on the coronary artery branch central line, Empirical Mode Decomposition (EMD) is carried out on the coronary artery branch diameter with the length larger than the preset branch length;

and when the EMD result is larger than the preset mode, removing the mode with the maximum fluctuation, adding the residual mode data, and determining the residual mode data as the coronary artery branch diameter sequence corresponding to each discrete point on the central line of the coronary artery branch.

Images