CN115910353A - Coronary artery microcirculation vascular resistance obtaining method and system based on layered myocardium model - Google Patents
Coronary artery microcirculation vascular resistance obtaining method and system based on layered myocardium model Download PDFInfo
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Abstract
The invention relates to a coronary artery microcirculation vascular resistance obtaining method and system based on a layered myocardial model, the method comprises the steps of establishing a coronary artery vascular model by medical images; collateral blood vessels are generated for coronary arteries; both coronary vessels and collateral vessels are taken as main vessels, the outer surface of the myocardial model is constructed in a fitting manner according to the outlet position of the main vessel, the inner surface of the myocardial model is established based on the principle similar to the outer surface, and the volume of the model is ensured to be the myocardial volume value; carrying out layered interpolation by using an ellipsoid; selecting a point P in the outermost layer, and connecting the point P with the outlet of the main blood vessel to generate a microcirculation blood vessel; selecting a point T outside the current layer, and generating a branched microcirculation blood vessel by matching with the nearest microcirculation blood vessel; gradually advancing to the inner layer to form bifurcation, and ensuring the bifurcation times of each layer; and calculating the resistance value of the outlet of the main blood vessel. Compared with the prior art, the invention considers the distribution of coronary artery in each layer of myocardium under the real condition, so that the calculated resistance value is more accurate and has the specificity of a patient.
Description
Technical Field
The invention relates to the technical field of vascular resistance acquisition, in particular to a coronary artery microcirculation vascular resistance acquisition method and system based on a layered myocardium model.
Background
The main cause of coronary heart disease is coronary stenosis due to arteriosclerosis. The Fractional Flow Reserve (FFR) refers to the ratio of the maximum blood flow obtained by the myocardial area of the blood vessel in the coronary artery with stenotic lesion to the maximum blood flow obtained by the same area under the theoretically normal condition, and can be simplified into the ratio of the average pressure (Pd) in the stenotic distal coronary artery to the average pressure (Pa) in the coronary artery oral aorta in the maximal hyperemia state of the myocardium. The FFR can indicate the influence of coronary artery stenosis lesion on distal blood flow and is used for evaluating whether the myocardium is ischemic, and the FFR becomes a recognized index for functional evaluation of coronary artery stenosis.
When the FFR is determined, the FFR is calculated by obtaining the mean pressure in the coronary artery at the distal end of the stenosis by different means based on the blood flow velocity in the maximal hyperemia state of the myocardium and the mean pressure in the aorta at the mouth of the coronary artery. At present, the FFR acquisition mode is mostly intrusive, the risk is high, and the cost is expensive. In order to solve the above problems, researchers have proposed a non-invasive FFR measurement mode combining coronary CTA and Computational Fluid Dynamics (CFD);
a system and method for simulating fractional flow reserve calculation using computational fluid dynamics is disclosed in the invention with publication No. CN 106650267B. The system comprises: the blood vessel tree model generation module is used for acquiring a medical image, executing segmentation and reconstructing a geometric model of an individual blood vessel tree; the computational grid generating module is used for generating computational grids for the geometric model and establishing a CFD model of the blood vessel tree; the boundary condition setting module is used for setting corresponding inlet and outlet boundary conditions for the CFD model of the blood vessel tree; the attribute setting module is used for setting the physical attribute and the flow equation of the blood; the solver is used for solving the CFD model of the blood vessel tree based on the inlet and outlet boundary conditions, the set physical properties and the set flow equation so as to obtain fluid parameters of all parts of the blood vessel tree; and a post-processing module for post-processing the fluid parameters to obtain a fractional flow reserve, the inlet and outlet boundary conditions being individual-specific.
The scheme also specifically introduces the outlet boundary condition as the microvascular resistance at each outlet of the whole individual vascular tree, and currently, for the calculation of the microvascular resistance, a pressure guide wire with a temperature sensor is generally adopted in the prior art to measure related parameters so as to obtain a coronary microvascular resistance index value. However, the process of measuring relevant parameters by using the pressure guide wire with the temperature sensor to obtain the coronary artery microvascular resistance index requires complex operations by a doctor, which greatly increases the workload of the doctor.
In order to solve the problem, the invention with the publication number of CN111627002A discloses a coronary artery microvascular resistance index calculation device and a method. The coronary microvascular resistance index calculation means includes: the aortic pressure acquisition module is used for acquiring aortic pressure; the DSA image acquisition module is used for acquiring a coronary DSA image sequence; the change curve generation module is connected with the DSA image acquisition module and is used for generating a contrast agent area change curve according to the imaging area of a contrast agent in a plurality of target frames and the imaging time of the target frames; the curve slope acquisition module is connected with the change curve generation module and is used for acquiring the average slope of the contrast agent area change curve; and the resistance index calculation module is connected with the aortic pressure acquisition module and the curve slope acquisition module and is used for calculating the coronary microvascular resistance index according to the aortic pressure and the average slope.
According to the method, the coronary artery microvascular resistance index is calculated through the average slope of a contrast agent area change curve and the aortic pressure, large measurement errors exist in the acquisition of the area of the contrast agent and the measurement of the aortic pressure, the coronary artery microvascular is difficult to capture from a coronary artery DSA image sequence, and the accuracy of the acquired coronary artery microvascular and the resistance thereof is difficult to guarantee.
Disclosure of Invention
The invention aims to overcome the defect of poor accuracy of the acquired coronary artery micro-vessels and the resistance thereof in the prior art, and provides a method and a system for acquiring the resistance of the coronary artery micro-vessels based on a layered myocardial model, which consider the distribution of coronary arteries among all layers of a myocardial under a real condition.
The purpose of the invention can be realized by the following technical scheme:
a coronary artery microcirculation vascular resistance obtaining method based on a layered myocardium model comprises the following steps:
s1: acquiring a medical image, and extracting and establishing a coronary artery blood vessel model, a cross section of the aortic root and the total volume of the myocardium;
s2: generating collateral blood vessels upstream and downstream of each coronary in the coronary vessel model;
s3: all the coronary vessels and the collateral vessels are taken as main vessels, and the position coordinate and the vessel radius of the outlet of each main vessel are obtained;
s4: fitting and constructing a myocardial outer wall equation according to the position coordinates of each main body blood vessel outlet and an ellipsoid equation, and then combining the cross section of the aortic root to obtain the myocardial outer wall surface;
s5: constructing the inner wall surface of the cardiac muscle according to the outer wall surface of the cardiac muscle on the basis of the principle that the outer wall surface of the cardiac muscle is similar to the inner wall surface of the cardiac muscle, and enabling the volume enclosed by the outer wall surface of the cardiac muscle, the inner wall surface of the cardiac muscle and the cross section where the aortic root is located to be equal to the total volume of the cardiac muscle, so that a cardiac muscle model is formed;
s6: carrying out interpolation in internal layers of the myocardial model by using an ellipsoid, and distributing the thickness for each layer;
s7: respectively carrying out grid division on each layer of the myocardial model to obtain a point cloud file of each layer;
s8: randomly selecting a point P in a point cloud file at the outermost layer of the myocardial model, pre-connecting the point P with outlets of all main blood vessels, and selecting a section of blood vessel generated by connection from the pre-connection according to the principle that the total volume of the generated blood vessel is minimum to serve as a microcirculation blood vessel;
s9: repeating the step S8 until each main blood vessel outlet generates a section of microcirculation blood vessel;
s10: randomly selecting points T in a current layer and a myocardial model point cloud file outside the current layer, screening m microcirculation blood vessels nearest to the points T for pre-connection, selecting points K to respectively connect the points T and upstream and downstream microcirculation blood vessels in the microcirculation blood vessels according to the principle that the total pressure drop of each branch under the same main body blood vessel outlet is equal and the total volume of the microcirculation blood vessels is minimum, and setting the radius of the newly generated blood vessel of each microcirculation blood vessel by combining the power-of-area bifurcation rule; comparing the total volume of all the blood vessel trees formed after the pre-connection, and keeping the pre-connection condition with the minimum total volume of the blood vessel trees, wherein the blood vessel trees comprise coronary arteries, collateral blood vessels and microcirculation blood vessels;
s11: repeating the step S10 until the bifurcation number of the newly generated bifurcation type multiple microcirculation blood vessels in the point cloud file of the layer of the myocardial model reaches the preset bifurcation times;
s12: taking a layer on the inner side of the current layer as the current layer, repeating the step S11, and gradually advancing to the innermost layer until the radiuses of all blood vessel outlets in the generated blood vessel tree are smaller than a preset blood vessel threshold;
s13: and calculating the resistance value of each outlet of the main blood vessel according to the blood vessel tree acquired in the step S12.
Further, in step S6, each layer is assigned a thickness in a linearly varying manner from the inside to the outside.
Further, in step S10, the blood vessel radius of each newly generated microcirculation blood vessel is set by combining the area bifurcation power law rule specifically as follows:
the generated branched microcirculation blood vessels comprise a K-upstream blood vessel, a K-downstream blood vessel and a K-T blood vessel, wherein the blood vessel radius of the K-upstream blood vessel is equal to the blood vessel radius of the outlet of the main blood vessel, the blood vessel radii of the K-downstream blood vessel and the K-T blood vessel are equal, and the calculation expressions of the blood vessel radii of the K-downstream blood vessel and the K-T blood vessel are as follows:
in the formula, R T Is the vessel radius of K-T vessel, R P Is the vessel radius of the K-downstream vessel, R i Is the vessel radius of the K-upstream vessel, and gamma is the bifurcation power law.
Further, the point K is selected according to the principle that the total pressure drop of each branch under the same main body blood vessel outlet is equal and the total volume of the microcirculation blood vessel is minimum:
according to the principle that the total pressure drop of each branch under the outlet of the same main blood vessel is equal, the length and the cross sectional area of a selected point K are respectively the same as those of blood vessels connected with the upstream and the downstream in the microcirculation blood vessel; and according to the principle that the total volume of the microcirculation blood vessels is minimum, the selected point K meets the condition that the total volume of the blood vessels respectively connected with the point T and the upstream and downstream blood vessels in the microcirculation blood vessels is minimum.
Further, step S2 specifically includes:
determining the number of increased collateral blood vessels and the vessel radius of each collateral blood vessel and the corresponding bifurcation power law according to the vessel radius of the upstream and downstream of each coronary artery in the coronary vessel model, wherein the increased collateral blood vessels are uniformly distributed at the upstream and downstream of the corresponding coronary artery;
the relation between the number of the increased collateral blood vessels, the vessel radius of each collateral blood vessel and the corresponding bifurcation power law is as follows:
Rh γ -Rd γ ＝n×R γ
wherein Rh is the upstream vessel radius of the coronary artery, rd is the downstream vessel radius of the coronary artery, γ is the bifurcation power law, n is the number of collateral vessels, and R is the vessel radius of the collateral vessels.
Further, the method for acquiring coronary artery end microcirculation vascular resistance further comprises the following steps: acquiring a region of a heart cavity through the medical image, and discarding the pre-connection if the pre-connected blood vessel passes through the region of the heart cavity in the pre-connection process in the steps S8 and S10;
if the vessel radius of the generated microcirculation vessel is smaller than half of the vessel threshold in step S10, discarding the pre-connection condition with the corresponding microcirculation vessel.
Further, in step S13, the calculating the resistance value of each outlet of the main vessel is specifically: calculating the resistance of each microcirculation blood vessel based on Poisea theorem, and then calculating the resistance of each blood vessel outlet in the blood vessel tree according to a series-parallel connection rule, wherein the resistance is equivalent to resistance, and the calculation expression of the resistance of each microcirculation blood vessel is as follows:
where R is the resistance, μ is the blood viscosity, L is the length of the blood vessel, and A is the cross-sectional area of the blood vessel.
Further, in step S13, the calculating the resistance value of each outlet of the main vessel is specifically:
determining the resistance of each blood vessel outlet in the blood vessel tree by calculating the capacitance and/or the inductance of each blood vessel, wherein the capacitance of each blood vessel is calculated by the following expression:
wherein C is capacitance, A is the cross-sectional area of the blood vessel, L is the length of the blood vessel, rho is the blood density, and a is the pulse wave velocity;
the computational expression of the inductance of the blood vessel is as follows:
in the formula, I is an inductor.
Further, the resistance of each blood vessel exit in the blood vessel tree obtained in step S13 is used to set exit boundary conditions of the three-dimensional CFD model of the blood vessel tree.
The invention also provides a coronary micro-circulation vascular resistance acquisition system based on the layered myocardial model, which comprises a memory and a processor, wherein the memory stores a computer program, and the processor calls the computer program to execute the steps of the method.
Compared with the prior art, the invention has the following advantages:
(1) In the process of establishing the microcirculation blood vessel tree model, the invention fully considers the distribution of coronary artery among all layers of the myocardium under the real condition, extracts the parameters of the myocardium volume with the specificity of a patient, the trunk running of the coronary artery, the sectional area of the coronary artery and the like, establishes a layered myocardium model, respectively grows the microcirculation blood vessel in each layer of the myocardium model, and ensures the number of newly added branches in each layer, so that the resistance value calculated based on the microcirculation blood vessel model is more accurate and has the specificity of the patient.
The resistance value calculated by the method enables a numerical simulation model for calculating the fractional flow reserve to have more accurate outlet boundary conditions with specificity of a patient, and accordingly coronary artery FFR obtained by numerical simulation is more accurate.
(2) The coronary vessel can be obtained through medical images such as CTA images, but the existing medical images are not accurate enough and difficult to observe clearly for the collateral vessels and the coronary tail end microcirculation vessels, so that the collateral vessels and the coronary tail end microcirculation vessels are regenerated according to the distribution rule of the collateral vessels and the coronary tail end microcirculation vessels and based on cardiac muscle and the coronary vessels, the resistance of the coronary tail end microcirculation vessels is calculated, and the accuracy of the calculation result can be greatly improved.
(3) The radius of all blood vessel outlets in the blood vessel tree is generally smaller than a blood vessel threshold, and the reduction of the radius of the blood vessel is generally realized by bifurcation and according to the area bifurcation power law rule; in order to generate a branched blood vessel, firstly, randomly selecting a point P from a point cloud file of a myocardial model to be connected with an outlet of a main blood vessel to generate a microcirculation blood vessel; and then randomly selecting a point T to connect with the adjacent microcirculation blood vessels to form a three-point combination of the point T and the upstream and downstream in a certain microcirculation blood vessel, and selecting a point K to respectively connect with the point T and the upstream and downstream in a certain microcirculation blood vessel according to the principle that the total pressure drop of each branch is equal to form a plurality of forked microcirculation blood vessels, so that the established coronary artery end microcirculation blood vessel is close to the real coronary artery microcirculation blood vessel distribution characteristics in geometry and function.
(4) The invention determines the starting point of the growth of the microcirculation blood vessel and the initial sectional area of the microcirculation blood vessel based on the coronary artery trunk with the added collateral blood vessel with the specificity of the patient, generates a coronary artery microcirculation blood vessel model in the extracted cardiac muscle model, fully considers the blood supply condition of the coronary artery to the cardiac muscle, ensures that the established microcirculation blood vessel model is close to the real coronary artery microcirculation blood vessel distribution characteristic in geometry and function, and ensures that the resistance value calculated based on the microcirculation blood vessel model is more accurate and has the specificity of the patient.
Drawings
Fig. 1 is a schematic flow chart of a coronary artery microcirculation vascular resistance obtaining method based on a layered myocardium model according to an embodiment of the present invention;
FIG. 2 is a schematic illustration of a coronary vessel, a collateral vessel, and a coronary end microcirculation vessel provided in an embodiment of the present invention;
fig. 3 is a schematic diagram of a coronary artery model provided in an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The embodiment provides a coronary artery microcirculation vascular resistance obtaining method based on a layered myocardium model, which comprises the following steps:
s1: acquiring a medical image, and extracting and establishing a coronary artery blood vessel model, a cross section of the aortic root and the total volume of the myocardium;
the invention considers that coronary blood vessels can be obtained through medical images such as CTA images, the distribution of the coronary blood vessels is shown in figure 3, but for collateral blood vessels and coronary tail end microcirculation blood vessels, the existing medical images are not accurate enough and are difficult to observe clearly, so the invention regenerates the collateral blood vessels and the coronary tail end microcirculation blood vessels according to the distribution rule of the collateral blood vessels and the coronary tail end microcirculation blood vessels based on cardiac muscle and the coronary blood vessels, aims to construct the distribution of the blood vessels shown in figure 2, calculates the resistance of the coronary tail end microcirculation blood vessels, and can greatly improve the accuracy of the calculation result.
S2: generating collateral blood vessels upstream and downstream of each coronary in the coronary vessel model;
the step S2 specifically comprises the following steps:
determining the number of increased collateral blood vessels, the vessel radius of each collateral blood vessel and a corresponding bifurcation power law according to the vessel radius of the upstream and downstream of each coronary in the coronary vessel model, wherein the increased collateral blood vessels are uniformly distributed at the upstream and downstream of the corresponding coronary;
the relationship between the number of collateral blood vessels to be increased, the vessel radius of each collateral blood vessel and the corresponding bifurcation power law is:
Rh γ -Rd γ ＝n×R γ
in the formula, rh is the upstream vessel radius of the coronary artery, rd is the downstream vessel radius of the coronary artery, gamma is the bifurcation power law, n is the number of collateral vessels, and R is the vessel radius of the collateral vessels.
S3: all coronary vessels and collateral vessels are taken as main body vessels, and the position coordinate and the vessel radius of the outlet of each main body vessel are obtained;
s4: fitting and constructing a myocardial outer wall equation according to the position coordinates of each main blood vessel outlet and an ellipsoid equation, and then combining the cross section where the aortic root is located to obtain the myocardial outer wall surface;
s5: based on the principle that the outer wall surface of the cardiac muscle is similar to the inner wall surface of the cardiac muscle, the inner wall surface of the cardiac muscle is constructed according to the outer wall surface of the cardiac muscle, and the volume enclosed by the outer wall surface of the cardiac muscle, the inner wall surface of the cardiac muscle and the cross section where the aortic root is located is equal to the total volume of the cardiac muscle, so that a cardiac muscle model is formed;
s6: performing interpolation by using an ellipsoid in internal layers of the myocardium model, and distributing thickness for each layer;
s7: respectively carrying out grid division on each layer of the myocardial model to obtain a point cloud file of each layer;
s8: randomly selecting a point P in a point cloud file at the outermost layer of the myocardial model, pre-connecting the point P with outlets of main blood vessels, and selecting a section of blood vessel generated by connection from the pre-connection according to the principle that the total volume of the generated blood vessel is minimum to serve as a microcirculation blood vessel;
s9: repeating the step S8 until each main blood vessel outlet generates a section of microcirculation blood vessel;
s10: randomly selecting points T in a current layer and a myocardial model point cloud file outside the current layer, screening m microcirculation blood vessels nearest to the points T for pre-connection, selecting points K according to the principle that the total pressure drop of branches under the same main body blood vessel outlet is equal and the total volume of the microcirculation blood vessels is minimum for each pre-connected microcirculation blood vessel, respectively connecting the points T and the upstream and downstream in the microcirculation blood vessel, then selectively deleting or not deleting the microcirculation blood vessel, finally newly generating a plurality of bifurcation type microcirculation blood vessels, and setting the blood vessel radius of each newly generated microcirculation blood vessel by combining an area bifurcation power law rule; comparing the total volume of all the blood vessel trees formed after pre-connection, and keeping the pre-connection condition of the minimum total volume of the blood vessel trees, wherein the blood vessel trees comprise coronary artery, collateral blood vessels and microcirculation blood vessels;
the point K is selected according to the principle that the total pressure drop of each branch under the same main body blood vessel outlet is equal and the total volume of the microcirculation blood vessel is minimum:
according to the principle that the total pressure drop of each branch under the outlet of the same main blood vessel is equal, the length and the cross sectional area of a selected point K are respectively the same as those of blood vessels connected with the upstream and the downstream in the microcirculation blood vessel; according to the principle that the total volume of the microcirculation blood vessel is minimum, the selected point K meets the condition that the total volume of the blood vessel connected with the point T and the blood vessel at the upstream and the downstream in the microcirculation blood vessel is minimum.
The specific blood vessel radius of each newly generated microcirculation blood vessel is set by combining the area bifurcation power law rule as follows:
the generated plurality of branched microcirculation blood vessels comprise a K-upstream blood vessel, a K-downstream blood vessel and a K-T blood vessel, wherein the blood vessel radius of the K-upstream blood vessel is equal to the blood vessel radius of the outlet of the main blood vessel, the blood vessel radii of the K-downstream blood vessel and the K-T blood vessel are equal, and the calculation expression of the blood vessel radii of the K-downstream blood vessel and the K-T blood vessel is as follows:
in the formula, R T Is the vessel radius of K-T vessel, R P Is the vessel radius of the K-downstream vessel, R i The radius of the blood vessel of the upstream blood vessel is K-, and gamma is a bifurcation power law;
s11: repeating the step S10 until the bifurcation number of the newly generated bifurcation type multiple microcirculation blood vessels in the point cloud file of the layer of the myocardial model reaches the preset bifurcation times;
s12: taking a layer on the inner side of the current layer as the current layer, repeating the step S11, and gradually advancing to the innermost layer until the radiuses of all blood vessel outlets in the generated blood vessel tree are smaller than a preset blood vessel threshold;
the radiuses of all blood vessel outlets in the blood vessel tree are generally smaller than a blood vessel threshold value, and the reduction of the radius of the blood vessel is generally realized through bifurcation and according to an area bifurcation power law rule; in order to generate a branched blood vessel, firstly, randomly selecting a point P from a point cloud file of a myocardial model to be connected with an outlet of a main blood vessel to generate a microcirculation blood vessel; then randomly selecting a point T to connect with the nearby microcirculation blood vessels to form a three-point combination of the point T and the upstream and downstream in a certain microcirculation blood vessel, selecting a point K to respectively connect with the point T and the upstream and downstream in a certain microcirculation blood vessel according to the principle that the total pressure drop of each branch is equal to form a plurality of branch microcirculation blood vessels, and thus establishing the coronary artery end microcirculation blood vessel close to the real coronary artery microcirculation blood vessel distribution characteristics in both geometry and function. The blood vessels generated in the method are assumed to be linear and have a circular cross section.
S13: and calculating the resistance value of each outlet of the main blood vessel according to the blood vessel tree acquired in the step S12.
In step S13, calculating the resistance value of each outlet of the main blood vessel specifically includes: calculating the resistance of each microcirculation blood vessel based on Poisea theorem, then calculating the resistance of each blood vessel outlet in the blood vessel tree according to a series-parallel connection rule, wherein the resistance is equivalent to resistance, and the calculation expression of the resistance of each microcirculation blood vessel is as follows:
where R is the resistance, μ is the blood viscosity, L is the length of the blood vessel, and A is the cross-sectional area of the blood vessel.
In step S13, the method of steps S1-S12 may also be used to calculate the capacitance and/or inductance of the blood vessel, so as to calculate the resistance of each blood vessel outlet, and the calculation of the resistance of the blood vessel outlet through the resistance, the capacitance, and the inductance has been disclosed in the prior art.
Calculating the resistance value of each outlet of the main blood vessel specifically comprises the following steps:
determining the resistance of each blood vessel outlet in the blood vessel tree by calculating the capacitance and/or the inductance of each blood vessel, wherein the calculation expression of the capacitance of each blood vessel is as follows:
wherein C is capacitance, A is the cross-sectional area of the blood vessel, L is the length of the blood vessel, rho is the blood density, and a is the pulse wave velocity;
the computational expression of the inductance of a blood vessel is:
in the formula, I is an inductor.
The method for acquiring the coronary artery end microcirculation vascular resistance further comprises the following steps: acquiring a region of a heart cavity through the medical image, and discarding the pre-connection if the pre-connected blood vessel passes through the region of the heart cavity in the pre-connection process in the steps S8 and S10;
if the vessel radius of the generated microcirculation vessel is smaller than half of the vessel threshold in step S10, discarding the pre-connection condition with the corresponding microcirculation vessel.
To sum up, in the process of establishing the microcirculation blood vessel tree model, the method fully considers the distribution of coronary artery among all layers of myocardium under the real condition, extracts parameters with the specificity of a patient, such as myocardial volume, the trunk running of the coronary artery, the sectional area of the coronary artery, and the like, establishes a layered myocardium model, respectively grows microcirculation blood vessels in each layer of the myocardium model, and ensures the number of newly added branches in each layer, so that a resistance value calculated based on the microcirculation blood vessel model is more accurate and has the specificity of the patient.
The method determines the starting point of the growth of the microcirculation blood vessel and the initial sectional area of the microcirculation blood vessel based on the coronary artery trunk with the added collateral blood vessel having the specificity of the patient, generates a coronary artery microcirculation blood vessel model in the extracted cardiac muscle model, fully considers the blood supply condition of the coronary artery to the cardiac muscle, ensures that the established microcirculation blood vessel model is close to the real coronary artery microcirculation blood vessel distribution characteristic in geometry and function, and ensures that the resistance value calculated based on the microcirculation blood vessel model is more accurate and has the specificity of the patient.
The resistance value calculated by the method enables a numerical simulation model for calculating the fractional flow reserve to have more accurate outlet boundary conditions with specificity of a patient, and accordingly coronary artery FFR obtained by numerical simulation is more accurate.
The embodiment also provides a coronary artery microcirculation vascular resistance acquisition system based on the layered myocardium model, which comprises a memory and a processor, wherein the memory stores a computer program, and the processor calls the computer program to execute the steps of the coronary artery microcirculation vascular resistance acquisition method based on the layered myocardium model.
In this embodiment, a specific implementation process of the coronary artery microcirculation vascular resistance obtaining method based on the hierarchical myocardial model is as follows:
(1) From the CTA images, the corresponding coronary vessel model was obtained, as well as the cross-section of the aortic root.
(2) The number n (1-7) of the increased collateral blood vessels, the area A of each collateral and the corresponding bifurcation power law gamma (1.7-3) are determined according to the upstream (Ap) and downstream (Ad) areas of each coronary artery.
Ap γ -Ad γ ＝n×A γ
(3) The increased collateral blood vessels are evenly distributed between upstream and downstream.
(4) The area and position coordinates of each coronary outlet (including newly added collateral vessels) are obtained.
(5) And (3) fitting an outer wall equation of the myocardium based on an ellipsoid equation by using the position coordinates obtained in the step (4), and obtaining a final outer wall surface of the myocardium by using the cross section in the step (1).
(6) Based on a similar principle, an ellipsoid surface of the inner wall surface of the cardiac muscle is constructed, so that the volume of a part surrounded by the two surfaces and the cross section in the step (1) is equal to the total volume of the cardiac muscle. The space enclosed by the three surfaces is the final myocardial model.
(7) The obtained myocardial model is subjected to a layering operation using ellipsoidal interpolation, and the thickness is assigned to each layer in a linearly varying manner from the inside to the outside. Linear variation factor range: 0-2, total number of layers: 10 to 30.
(8) And carrying out mesh division on each layer of the myocardial model to obtain respective point cloud files.
(9) The angiogenesis process is carried out from the outermost layer to the innermost layer, when the angiogenesis is generatedThe radius of all outlet section (terminal) vessels of the vessel tree model is less than a threshold value r min (2-10 μm) to complete the generation of the whole coronary artery model.
(10) And randomly taking a point P in the point cloud model of the outmost myocardium as an exit point of the blood vessel section to be generated. Point P and each coronary outlet (area A) i ) Pre-ligation (direct discard through the lumen) was performed, the resulting vessel lengths being L each i And then selecting the microcirculation blood vessel connected as a section of generated blood vessel (the area of the blood vessel is the area of the selected coronary artery outlet) by the principle of minimum total volume of generated blood vessels.
(11) And (4) repeating the step (10) until each outlet generates a section of microcirculation blood vessel.
(12) And continuously randomly taking a point T in the layer of myocardial model, screening m microcirculation blood vessels nearest to the point T for pre-connection (directly abandoning the situation of passing through a cavity), finding a bifurcation point in the myocardium, which enables the total volume of the blood vessel tree to be the minimum under the connection situation, according to the principle that the total pressure drop of all branches under the same coronary artery outlet is equal, combining the power law of area bifurcation, completing the optimization under the connection, taking the bifurcation point as a primary connection result, comparing the total volumes of the blood vessel trees generated by all pre-connections, and taking the minimum situation as a final optimization result (if the radius of the blood vessel generated by the connection is smaller than half of the threshold value in the range of (9), abandoning the situation).
(13) Repeating the step (12) until the layer is branched at least N times (2-10) from the upper layer to the layer, and gradually advancing to the innermost layer until the termination condition is met.
(14) And calculating the resistance (resistance R) of each generated blood vessel based on Poisea theorem, and calculating the equivalent resistance value of each coronary artery outlet by combining the series-parallel connection rule of the resistance. The compliance (capacitance C) and inertia (inductance I) of each generated blood vessel are calculated by the following formulas, and the equivalent capacitance and the equivalent inductance of each coronary artery outlet are calculated by combining a series-parallel connection rule. (A, L, μ, ρ, a represent the cross-sectional area of the blood vessel, the length of the blood vessel, the viscosity of the blood, the density of the blood, and the velocity of the pulse wave, respectively).
The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations can be devised by those skilled in the art in light of the above teachings. Therefore, the technical solutions that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the prior art according to the concepts of the present invention should be within the scope of protection determined by the claims.
Claims (10)
1. A coronary artery microcirculation vascular resistance obtaining method based on a layered myocardial model is characterized by comprising the following steps:
s1: acquiring a medical image, and extracting and establishing a coronary artery blood vessel model, a cross section where the root of the aorta is located and the total volume of the myocardium;
s2: generating collateral blood vessels upstream and downstream of each coronary in the coronary vessel model;
s3: all the coronary vessels and the collateral vessels are taken as main vessels, and the position coordinate and the vessel radius of the outlet of each main vessel are obtained;
s4: fitting and constructing a myocardial outer wall equation according to the position coordinates of each main body blood vessel outlet and an ellipsoid equation, and then combining the cross section of the aortic root to obtain the myocardial outer wall surface;
s5: constructing the inner wall surface of the cardiac muscle according to the outer wall surface of the cardiac muscle on the basis of the principle that the outer wall surface of the cardiac muscle is similar to the inner wall surface of the cardiac muscle, and enabling the volume enclosed by the outer wall surface of the cardiac muscle, the inner wall surface of the cardiac muscle and the cross section where the aortic root is located to be equal to the total volume of the cardiac muscle, so that a cardiac muscle model is formed;
s6: carrying out interpolation in internal layers of the myocardial model by using an ellipsoid, and distributing the thickness for each layer;
s7: respectively carrying out grid division on each layer of the myocardial model to obtain a point cloud file of each layer;
s8: randomly selecting a point P from the point cloud file at the outermost layer of the myocardial model, pre-connecting the point P with outlets of all main blood vessels, and selecting a section of blood vessel generated by connection from the pre-connection according to the principle that the total volume of the generated blood vessel is minimum to serve as a microcirculation blood vessel;
s9: repeating the step S8 until each main blood vessel outlet generates a section of microcirculation blood vessel;
s10: randomly selecting points T in a current layer and a myocardial model point cloud file outside the current layer, screening m microcirculation blood vessels nearest to the points T for pre-connection, selecting points K to respectively connect the points T and upstream and downstream microcirculation blood vessels in the microcirculation blood vessels according to the principle that the total pressure drop of each branch under the same main body blood vessel outlet is equal and the total volume of the microcirculation blood vessels is minimum, and setting the radius of the newly generated blood vessel of each microcirculation blood vessel by combining the power-of-area bifurcation rule; comparing the total volume of all the blood vessel trees formed after the pre-connection, and keeping the pre-connection condition with the minimum total volume of the blood vessel trees, wherein the blood vessel trees comprise coronary arteries, collateral blood vessels and microcirculation blood vessels;
s11: repeating the step S10 until the bifurcation number of the newly generated bifurcation type multiple microcirculation blood vessels in the point cloud file of the layer of the myocardial model reaches the preset bifurcation times;
s12: taking a layer on the inner side of the current layer as the current layer, repeating the step S11, and gradually advancing to the innermost layer until the radiuses of all blood vessel outlets in the generated blood vessel tree are smaller than a preset blood vessel threshold;
s13: and calculating the resistance value of each outlet of the main blood vessel according to the blood vessel tree acquired in the step S12.
2. The method for acquiring coronary artery microcirculation vascular resistance based on the layered myocardial model of claim 1, wherein in step S6, the thickness is allocated to each layer in a linear change manner from inside to outside.
3. The coronary artery microcirculation blood vessel resistance obtaining method based on the layered myocardium model according to the claim 1, wherein in the step S10, the blood vessel radius of each newly generated microcirculation blood vessel is set by combining with the power law of area bifurcation as follows:
the generated branched microcirculation blood vessels comprise a K-upstream blood vessel, a K-downstream blood vessel and a K-T blood vessel, wherein the blood vessel radius of the K-upstream blood vessel is equal to the blood vessel radius of the outlet of the main blood vessel, the blood vessel radii of the K-downstream blood vessel and the K-T blood vessel are equal, and the calculation expressions of the blood vessel radii of the K-downstream blood vessel and the K-T blood vessel are as follows:
in the formula, R T Is the vessel radius of K-T vessel, R P Is the vessel radius of the K-downstream vessel, R i Is the vessel radius of the K-upstream vessel, and gamma is the bifurcation power law.
4. The coronary artery microcirculation blood vessel resistance obtaining method based on the layered myocardium model according to claim 1, wherein the points K are selected according to the principle that the total pressure drop of each branch under the same main body blood vessel outlet is equal and the total volume of the microcirculation blood vessel is minimum:
according to the principle that the total pressure drop of each branch under the outlet of the same main blood vessel is equal, the length and the cross sectional area of a selected point K are respectively the same as those of blood vessels connected with the upstream and the downstream in the microcirculation blood vessel; and according to the principle that the total volume of the microcirculation blood vessels is minimum, the selected point K meets the condition that the total volume of the blood vessels respectively connected with the point T and the upstream and downstream blood vessels in the microcirculation blood vessels is minimum.
5. The method for acquiring coronary artery microcirculation vascular resistance based on the layered myocardium model according to claim 1, wherein the step S2 specifically comprises:
determining the number of increased collateral blood vessels and the vessel radius of each collateral blood vessel and the corresponding bifurcation power law according to the vessel radius at the upstream and the downstream of each coronary in the coronary vessel model, wherein the increased collateral blood vessels are uniformly distributed at the upstream and the downstream of the corresponding coronary;
the relation between the number of the increased collateral blood vessels, the vessel radius of each collateral blood vessel and the corresponding bifurcation power law is as follows:
Rh γ -Rd γ ＝n×R γ
in the formula, rh is the upstream vessel radius of the coronary artery, rd is the downstream vessel radius of the coronary artery, gamma is the bifurcation power law, n is the number of collateral vessels, and R is the vessel radius of the collateral vessels.
6. The method for acquiring coronary artery microcirculation vascular resistance based on the layered myocardium model according to claim 1, wherein the method for acquiring coronary artery end microcirculation vascular resistance further comprises: acquiring a region of a heart cavity through the medical image, and discarding the pre-connection if the pre-connected blood vessel passes through the region of the heart cavity in the pre-connection process in the steps S8 and S10;
if the vessel radius of the generated microcirculation vessel is smaller than half of the vessel threshold in the step S10, discarding the pre-connection condition with the corresponding microcirculation vessel.
7. The method for obtaining coronary artery microcirculation vascular resistance based on the layered myocardium model according to claim 1, wherein in step S13, the calculating of the resistance value of each outlet of the main vessel specifically comprises: calculating the resistance of each microcirculation blood vessel based on Poisea theorem, and then calculating the resistance of each blood vessel outlet in the blood vessel tree according to a series-parallel connection rule, wherein the resistance is equivalent to resistance, and the calculation expression of the resistance of each microcirculation blood vessel is as follows:
wherein R is the resistance, μ is the blood viscosity, L is the length of the blood vessel, and A is the cross-sectional area of the blood vessel.
8. The method for obtaining coronary artery microcirculation vascular resistance based on the layered myocardium model according to claim 1, wherein in step S13, the calculating of the resistance value of each outlet of the main vessel specifically comprises:
determining the resistance of each blood vessel outlet in the blood vessel tree by calculating the capacitance and/or inductance of each blood vessel, wherein the calculation expression of the capacitance of each blood vessel is as follows:
wherein C is capacitance, A is the cross-sectional area of the blood vessel, L is the length of the blood vessel, rho is the blood density, and a is the pulse wave velocity;
the computational expression of the inductance of the blood vessel is as follows:
in the formula, I is an inductor.
9. The method according to claim 1, wherein the resistance of each blood vessel exit in the blood vessel tree obtained in step S13 is used to set exit boundary conditions of a three-dimensional CFD model of the blood vessel tree.
10. A coronary microcirculation vascular resistance acquisition system based on a hierarchical myocardial model, characterized by comprising a memory and a processor, said memory storing a computer program, said processor invoking said computer program to perform the steps of the method according to any of claims 1 to 9.
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