CN118576229A

CN118576229A - Flow model blood flow reserve fraction evaluation method and device based on bifurcation position

Info

Publication number: CN118576229A
Application number: CN202410302861.9A
Authority: CN
Inventors: 张贺晔; 高智凡; 刘修健; 谭志良; 王安邦
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2024-03-15
Filing date: 2024-03-15
Publication date: 2024-09-03

Abstract

The application provides a blood flow reserve fraction evaluation method and a device based on a flow model of a bifurcation position, which are used for acquiring target coronary angiography information and blood information of a target coronary; wherein the target angiography information comprises a target angiography image and a target angiography sequence containing the target angiography image; constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a blood vessel central line node parameter and a bifurcation node parameter; determining an inlet initial flow of a one-dimensional blood flow model according to a target angiography sequence; generating a fractional flow reserve of the target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or a bifurcation node. The method is quicker to solve, and the bypass blood flow is compensated at the actual bifurcation without reconstructing the bypass blood vessel structure, so that the problem of ignoring the bifurcation position information in the prior art is solved.

Description

Flow model blood flow reserve fraction evaluation method and device based on bifurcation position

Technical Field

The application relates to the field of medical detection, in particular to a fractional flow reserve evaluation method and device based on a flow model of a bifurcation position.

Background

Vascular stenosis is the first public enemy of human life health. However, the invasive FFR requires the use of a coronary pressure guide wire, which causes the problems of invasiveness, high cost and the like, and the clinical application of the FFR is greatly limited. Whereas FFR derived from Invasive Coronary Angiography (ICA), ICA-FFR, is a potential alternative, it may be of importance for assessment of coronary artery functionality without the use of pressure guidewires.

However, ICA-FFR has difficulty in acquiring information of collateral blood flow. Due to the limited angiographic view, the blood flow structure of the collateral vessels is difficult to reconstruct. Estimating collateral blood flow in the absence of collateral blood flow structure is also limited because information of bifurcation location is ignored.

Disclosure of Invention

In view of the problems, the present application has been made to provide fractional flow reserve assessment methods and apparatus of a bifurcation site based flow model that overcomes the problems or at least partially solves the problems, including:

A fractional flow reserve assessment method based on a flow model of a bifurcation site for calculating fractional flow reserve of a target node within a target vessel by invasive coronary angiography, the coronary artery comprising a main vessel and a collateral vessel, the junction of the main vessel and the collateral vessel being a bifurcation node, the target vessel being a main vessel, the method comprising:

acquiring target coronary angiography information and blood information of a target coronary artery; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image;

Constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter;

determining an inlet initial flow of the one-dimensional blood flow model according to the target angiography sequence;

generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or the bifurcation node.

Further, constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a centerline node parameter and a bifurcation node parameter, comprising:

Determining a blood vessel center line corresponding to the target blood vessel according to the target blood vessel angiography image; wherein the vessel centerline is comprised of a plurality of vessel centerline nodes and a plurality of bifurcation nodes;

reconstructing the target blood vessel according to the blood vessel center line to obtain the corresponding one-dimensional blood flow model;

Segmenting the one-dimensional blood flow model according to the bifurcation nodes to obtain a plurality of blood vessel segments;

Determining point parameters corresponding to the target node according to the target node and the blood vessel segment where the target node is located; wherein the point parameters include point coordinates, cross-sectional diameters and cross-sectional areas of the target nodes within the corresponding vessel segments.

Further, the step of determining the inlet initial flow of the one-dimensional blood flow model according to the target angiography sequence comprises the following steps:

Determining an initial vessel segment at the model inlet according to the one-dimensional blood flow model;

Determining the length of the initial blood vessel segment corresponding to the initial blood vessel segment according to the one-dimensional blood flow model;

Generating an overfilling speed of the initial blood vessel segment in a resting state according to the initial blood vessel segment length and the target angiography sequence;

And determining the inlet initial flow of the one-dimensional blood flow model according to the superfusion speed.

Further, the blood information includes a density and a kinematic viscosity of blood, and the generating a fractional flow reserve of the target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; the step of the target node being a center line node or a bifurcation node comprises the following steps:

when the target node is a bifurcation node, determining a point parameter of an upstream segment node of the target node and a point parameter of the target node according to the one-dimensional blood flow model;

generating flow state data of the target node according to the blood information, the inlet initial flow, the point parameter of the upstream segment node and the point parameter of the target node; wherein the flow state data includes flow rate and pressure of blood flow; the formula is as follows:

wherein Q, P, D and A are flow, pressure, cross-sectional diameter and cross-sectional area, respectively; the index a depends on the energy consumption; subscripts i and i+1 represent the variables of the upstream segment node and the downstream segment node, respectively; li is the length of segment i; (0) represents an entrance position z=0; (Li) represents the exit position z=li of segment i; nb is the number of bifurcation nodes; ρ is the density of blood;

And determining the corresponding fractional flow reserve according to the flow state data of the target node.

When the target node is a vessel centerline node, determining the diameter of a target vessel segment corresponding to the target node according to the one-dimensional blood flow model;

Determining a stenosis corresponding to the target vessel segment according to the diameter of the target vessel segment; wherein the stenotic conditions include normal and stenosis;

Generating flow state data of the target node according to the stenosis, the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the flow state data includes a flow rate and a pressure of blood;

Further, generating flow state data of the target node according to the stenosis condition, the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the flow state data includes a flow rate and a pressure of blood, comprising:

when the narrow condition of the target blood vessel segment is normal, determining the point parameter of the upstream segment node of the target node, the point parameter of the target node and the length of the target blood vessel segment according to the one-dimensional blood flow model;

generating flow state data of the target node according to the blood information, the inlet initial flow, the point parameter of the upstream segment node, the point parameter of the target node and the length of the target blood vessel segment: the formula is as follows:

Wherein the last term of the first equation is a friction term; z is the axial coordinate of the centerline node; ρ and μ are the density and viscosity of blood, respectively; l i is the length of segment i; (0) Representing the entrance position z=0, (Li) representing the exit position z= L i of segment i; d is the cross-sectional diameter.

When the stenosis of the target blood vessel segment is a stenosis, determining a point parameter of an upstream segment node of the target node, the point parameter of the target node and the stenosis length of the target blood vessel segment according to the one-dimensional blood flow model and the inlet initial flow;

Generating flow state data of the target node according to the blood information, the point parameter of the upstream segment node, the point parameter of the target node and the length of the narrow segment; the formula is as follows:

Wherein K t = 1.52; (0) Represents the entrance position z=0, (Zs) represents the narrowest position z=zs; l s is the length of the stenosis.

A fractional flow reserve assessment device based on a flow model of a bifurcation site for calculating fractional flow reserve of a target node within a target vessel by invasive coronary angiography, the coronary artery comprising a main vessel and a collateral vessel, the junction of the main vessel and the collateral vessel being a bifurcation node, the target vessel being a main vessel, comprising:

the information acquisition module is used for acquiring target coronary angiography information and blood information of a target coronary; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image;

The model construction module is used for constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter;

an inlet condition module for determining an inlet initial flow of the one-dimensional blood flow model according to the target angiography sequence;

A flow calculation module for generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or a bifurcation node.

An apparatus comprising a processor, a memory and a computer program stored on the memory and capable of running on the processor, which when executed by the processor, implements the steps of a fractional flow reserve assessment method of a bifurcation location based flow model as described above.

A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of a fractional flow reserve assessment method of a bifurcation site based flow model as described above.

The application has the following advantages:

In an embodiment of the present application, the present application provides a solution for calculating ICA-FFR based on a bifurcation site directed flow model (BLFM), in particular, with respect to the problem in the prior art that ICA-FFR is difficult to obtain information of collateral blood flow: acquiring target coronary angiography information and blood information of a target coronary artery; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image; constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter; determining an inlet initial flow of the one-dimensional blood flow model according to the target angiography sequence; generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or a bifurcation node. The ICA-FFR method solves the FFR value more rapidly, and can compensate the collateral blood flow at the actual bifurcation without reconstructing the geometry of the collateral blood vessel, thereby solving the problem of neglecting the information of the bifurcation position in the prior art and improving the estimation of the FFR value.

Drawings

In order to more clearly illustrate the technical solutions of the present application, the following brief description will be given of the drawings required for the description of the present application, which are merely examples of the present application, and from which other drawings can be obtained without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of the steps of a fractional flow reserve assessment method based on a flow model at a bifurcation site according to an embodiment of the present application;

FIG. 2 is a flow chart of a fractional flow reserve assessment method based on a bifurcation site based flow model in accordance with one embodiment of the present application;

FIG. 3 is a schematic diagram showing FFR calculation results and pullback curves of a typical blood vessel according to an embodiment of the present application;

FIG. 4 is a block diagram of a fractional flow reserve evaluation device based on a flow model of a bifurcation site according to an embodiment of the present application;

Fig. 5 is a schematic structural diagram of a computer device according to an embodiment of the present invention.

Detailed Description

In order that the manner in which the above recited objects, features and advantages of the present application are obtained will become more readily apparent, a more particular description of the application briefly described above will be rendered by reference to the appended drawings. It will be apparent that the described embodiments are some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

The inventors found by analyzing the prior art that: ICA-FFR is a diagnostic technique for measuring the local blood flow and pressure of the coronary arteries. It is used for diagnosing hemodynamic abnormalities caused by coronary artery stenosis. ICA-FFR is obtained by Invasive Coronary Angiography (ICA) and is considered as a gold standard for assessing the functional importance of coronary stenosis.

However, ICA-FFR faces difficulties in acquiring collateral blood flow information. ICA-FFR depends on the blood pressure field within the target vessel. This pressure field is affected by collateral blood flow. This blood flow depends on the blood flow shape of the collateral blood vessel. However, this blood flow shape is difficult to reconstruct due to the limited angiographic view. The limited viewing angle causes problems with foreshortening and overlapping of the vessels. This restriction prevents the reconstruction of the shape of the collateral blood flow.

Most existing methods only calculate the total collateral blood flow in the target vessel. They leak the total flow proportionally along the target vessel according to a polynomial leak function as follows:

prior art one, using an estimate of healthy vessel radius to determine the flow of a side branch:

this formula, even if smoothed in some cases, still has the problem of not distributing parent branch flow to the side branches, because it has a mass inflow that does not meet the physiological laws.

The average velocity and average cross-sectional area of a given vessel segment are used to calculate the average volumetric flow rate needed to solve the flow equation:

Q_prox＝v_{contrast averagc}×A_{proximal average}

Q_dist＝v_{contrast average}×A_{distal average}

This concept applies the assumption that the average velocity (V average) is constant in the target epicardial coronary segment. As the side branches separate, the volumetric flow (Q) will decrease in proportion to the decrease in cross-sectional area of the distal reference section (A DISTAL AVERAGE).

However, these methods still have difficulty calculating each bypass flow. They ignore the information of the bifurcation site. This also results in errors in collateral blood flow leakage. And the second prior art is built on a 3D blood flow model, which also makes the prior art extremely time and cost consuming.

Therefore, the prior art for calculating ICA-FFR still has certain drawbacks:

(1) The prior art calculates ICA-FFR, most methods calculate only the total collateral blood flow in the target vessel. I.e. leakage of total flow along the target vessel proportionally according to a polynomial leakage function. These methods still have difficulty calculating each collateral blood flow. Because they ignore the information of the bifurcation site, this also results in errors in collateral blood flow leakage.

(2) The construction of blood flow models in the prior art is mainly based on three-dimensional models. The solution requirement of multiple parameters for the N-S equation solution of the three-dimensional model also causes the defects of high cost and long time consumption in the solution process of FFR values.

In response to the existing shortcomings, the present invention proposes a method for calculating ICA-FFR based on a bifurcation site directed flow model (BLFM).

It should be noted that the present invention is used to calculate fractional flow reserve of a target node in a target vessel by invasive coronary angiography, the coronary artery includes a main vessel and a collateral vessel, the junction of the main vessel and the collateral vessel is a bifurcation node, and the target vessel is a main vessel.

The main blood vessel is the main channel of the vascular system and is responsible for the transport of blood from the heart to the various tissues and organs throughout the body. The main blood vessel is usually relatively coarse and has a large blood flow, which is the main path of blood circulation. The collateral blood vessel is a smaller branch which is separated from the main blood vessel, and the connection point between the branch blood vessel and the main blood vessel is a bifurcation node. The collateral blood vessel is responsible for providing a blood backup or shunt for the main blood vessel. When the main blood vessel is blocked or damaged, the collateral blood vessel can play a compensatory role, so that the blood can continue to flow to corresponding tissues and organs. The bifurcation nodes are located at the junction of the main and collateral vessels where blood flows to different vessels, respectively, depending on different requirements and pressure conditions.

Referring to fig. 1, there is shown a fractional flow reserve assessment method based on a flow model of a bifurcation site according to an embodiment of the present application, the method comprising:

S110, acquiring target coronary angiography information and blood information of a target coronary; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image;

S120, constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter;

s130, determining the initial inlet flow of the one-dimensional blood flow model according to the target angiography sequence;

S140, generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or a bifurcation node.

Next, a fractional flow reserve evaluation method of a flow model based on a bifurcation site in the present exemplary embodiment will be further described.

Acquiring target coronary angiography information and blood information of a target coronary artery as described in the step S110; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image.

ICA is a reference standard method for diagnosing obstructive Coronary Artery Disease (CAD). ICA injects contrast agent through the catheter to make coronary artery develop under X-ray, and after the contrast agent enters heart and coronary artery, coronary artery contrast information is obtained by X-ray machine, and can provide detailed structure of coronary artery and information about whether there is stenosis or not.

As an example, a one-dimensional blood flow model of the target coronary artery is constructed from a target angiographic image (i.e., ICA image) in a resting state. First, the present embodiment manually selects the best image key frame of the target angiographic image in the rest state according to the following criteria:

① The target angiographic image should have an orthogonal projection of the target coronary artery;

② The target vessel has minimal vessel overlap and foreshortening;

③ The contrast agent substantially fills the target vessel.

Next, lumen contours of the target vessel are delineated from the selected optimal image key frames. The centerline of the vessel and its corresponding diameter are then extracted from the two-dimensional lumen profile. A bypass vessel is defined as one having a diameter greater than one third of the diameter of the main vessel. The bifurcation nodes associated with these bypass vessels are marked on the centerline. These collateral blood vessels are considered important. To generate the computational domain, a one-dimensional geometric model is constructed based on the centerline and the local diameters.

Finally, the physical information of the blood itself may be obtained by obtaining usual blood information in clinical practice, or based on typical values in the physiological range reported in the literature, or using some accepted estimation method.

As described in the step S120, a corresponding one-dimensional blood flow model is constructed according to the target angiography image; wherein the one-dimensional blood flow model includes a vessel centerline node parameter and a bifurcation node parameter.

In one embodiment of the present invention, the step S120 of "constructing a corresponding one-dimensional blood flow model according to the target angiographic image" may be further described in conjunction with the following description; wherein the one-dimensional blood flow model comprises specific processes of a blood vessel centerline node parameter and a bifurcation node parameter.

Determining a blood vessel center line corresponding to the target blood vessel according to the target angiography image; wherein the vessel centerline is comprised of a plurality of vessel centerline nodes and a plurality of bifurcation nodes;

Reconstructing the target blood vessel according to the blood vessel center line to obtain a corresponding one-dimensional blood flow model;

segmenting the one-dimensional blood flow model according to the bifurcation node to obtain a plurality of blood vessel segments;

Determining a point parameter corresponding to the target node according to the target node and a blood vessel segment where the target node is located; wherein the point parameters include point coordinates, cross-sectional diameters and cross-sectional areas of the target nodes within the corresponding vessel segments.

As one example, referring to FIG. 2, a workflow diagram is calculated for the ICA-FFR based on BLFM. After the target angiography image is acquired, post-processing is carried out on the target angiography image through commercial software or an automatic algorithm so as to improve the image quality; the vessel region is then identified and located by image segmentation techniques which may employ techniques such as thresholding, region growing, level set methods, etc., to segment the main vessel from the target angiographic image. And then, according to the segmented image, adopting image processing technology such as edge detection, morphological analysis, curve fitting and the like to identify and extract the central line of the main blood vessel, wherein the central line of the blood vessel represents the geometric shape and trend of the blood vessel, and the method can be used for analyzing the blood flow condition of the coronary artery and further evaluating the stenosis degree of the coronary artery. After extracting the vessel centerline, since the vessel geometry may be approximated as a circle or cylinder, the vessel radius may be detected at various nodes along the centerline, and the algorithm may need to measure the vessel radius point by point (or at a timing as needed) to obtain the vessel diameter. Each point on the vessel centerline represents a location on the vessel surface, and the radius of the vessel can be obtained by calculating the distance from the point on the centerline to the vessel center. By measuring the radius of the blood vessel point by point, the change in radius along the centerline of the blood vessel can be obtained, thereby evaluating the stenosis degree and other morphological characteristics of the blood vessel. And finally dividing the blood vessel into a plurality of sections according to bifurcation nodes of the blood vessel, and detecting the stenosis of each blood vessel section by adopting an automatic stenosis detection algorithm. A one-dimensional blood flow model (BLFM) of the main vessel is constructed based on the centerlines and local diameters, and a computational domain is generated.

There are multiple bifurcation nodes in the main vessel, which can be determined by detecting the position of a significant change in curvature or the occurrence of a branch, from which the vessel can be divided into several independent segments. Each vessel segment ends from one point on the centerline to another bifurcation node (or vessel end). The point parameters of each node on the blood vessel central line are calculated through the one-dimensional blood flow model, and the blood vessel central line comprises a plurality of blood vessel central line nodes and a plurality of bifurcation nodes, so that the blood vessel central line node parameters of each blood vessel central line node and the bifurcation node parameters of each bifurcation node are calculated through the one-dimensional blood flow model.

It should be noted that, the present embodiment provides a method for calculating a fractional flow reserve of a node, and at this time, the corresponding fractional flow reserve can be calculated by obtaining the point parameter of the target node. Of course, the fractional flow reserve of a plurality of nodes can be calculated, and only the point parameter of each node is required to be acquired one by one, and the fractional flow reserve of each node is calculated according to the acquired point parameter.

An inlet initial flow of the one-dimensional blood flow model is determined from the target angiography sequence, as described in the step S130.

In one embodiment of the present invention, the specific procedure of "determining the initial flow of the inlet of the one-dimensional blood flow model according to the target angiography sequence" described in step S130 may be further described in connection with the following description.

Determining an initial vessel segment at the model inlet from the one-dimensional blood flow model, as described in the following steps;

Determining an initial vessel segment length corresponding to the initial vessel segment according to the one-dimensional blood flow model as follows;

Generating an over-perfusion rate of the initial vessel segment in a resting state as a function of the initial vessel segment length and the target angiographic sequence, as described below;

as described in the following steps, the initial inlet flow of the one-dimensional blood flow model is determined according to the superperfusion speed.

As an example, since a one-dimensional blood flow model establishes a relationship between the flow patterns (i.e., flow and pressure) at bifurcation nodes for an upstream segment (i.e., parent vessel) and a downstream segment (i.e., main vessel), such a relationship follows the laws of conservation of mass and conservation of momentum. In order to provide data support for flow state data calculations at any node of the downstream segment, it is therefore necessary to determine the inlet initial flow of the one-dimensional flow model.

Referring to fig. 2, the model is divided into several vessel segments by bifurcation nodes, and the initial flow at the model entrance is calculated from the TIMI Frame Count (TFC) vrest. TFC is performed under the same angiographic sequence as the previous key frame to obtain the contrast agent flow rate in the resting state. In particular, TIMI frame counting is a method for assessing coronary blood flow based on successive frames of coronary angiography by counting the number of frames required for a contrast agent to pass through a particular segment of the coronary artery to assess blood flow rate. The time (number of frames) required for the contrast agent to pass completely through the segment of blood vessel is recorded by observing the progress of the contrast agent flowing from the starting point to the distal point of the initial segment of blood vessel. The number of frames required for the contrast agent to pass completely through the initial vessel segment minus the number of frames of the starting point yields the TIMI frame count. This count represents the time required for the contrast agent to pass through the initial vessel segment. Finally, the resting rate of the resting coronary artery can be calculated based on the TIMI frame count and the length of the initial vessel segment. The calculation formula of the resting speed is: resting speed = vessel length/TIMI frame count x frame rate.

The resting rate is converted to an over-fill rate Vhyper using an empirical formula. I.e. the flow at the inlet is qin= Vhyper ·ain, where Ain is the cross-sectional area at the inlet.

Generating a fractional flow reserve of the target node from the one-dimensional blood flow model, the blood information and the inlet initial flow as described in the step S140; wherein the target node is a centerline node or a bifurcation node.

The blood information includes the density and the kinematic viscosity of blood.

As an example, the BLFM of the present invention is a one-dimensional blood flow model for calculating blood flow in the main coronary arteries. It can compensate for collateral blood flow at the actual bifurcation site without the need for collateral vessel geometry. In addition, BLFM leaks blood flow to arterioles according to a leak function. The model uses bifurcation fractal law to calculate the blood flow of collateral vessels and arterioles. This law states that the presence of collateral vessels and arterioles leads to a cone change in the main vessel. It describes the relationship between vessel diameters at the bifurcation as follows:

Wherein, D _PV,D_MB,D_SB is the diameter of parent vessel, main tributary vessel and collateral vessel respectively, and the relation between parent vessel and the main tributary vessel is: the upstream section of the target node is a parent vessel, and the downstream section is a main vessel; q is the flow; k is a constant; the index a depends on the energy consumption.

BLFM establishes the flow relationship between parent and main vessels directly according to equation (1):

Wherein Q _MB and Q _PV are the flow rates of the main and parent vessels, respectively.

The computational domain of BLFM includes a one-dimensional blood flow model of a single main coronary artery. This geometric model is divided into segments to compensate for collateral blood flow. The segments are interconnected by bifurcation nodes (i.e., the bifurcation sites of the collateral vessels). The BLFM then adopts a different approach to compensate for collateral blood flow at the bifurcation node and leak arteriole blood flow in the segment. Thus, BLFM consists of two parts: traffic at the bifurcation node and traffic within the segment. FIG. 2 shows the workflow of calculating ICA-FFR based on BLFM.

In one embodiment of the present invention, the generating the fractional flow reserve of the target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow rate in step S140 may be further described in conjunction with the following description; wherein the target node is a specific process of a centerline node or a bifurcation node ".

Generating flow state data of the target node according to the blood information, the inlet initial flow, the point parameter of the upstream segment node and the point parameter of the target node;

the corresponding fractional flow reserve is determined from the flow state data of the target node, as described in the following steps.

As an example, in the case where the target node is a bifurcation node, the present embodiment is a method of calculating the flow and pressure at the bifurcation node. Specifically, the one-dimensional blood flow model establishes a relationship between flow patterns (i.e., flow and pressure) at bifurcation nodes for an upstream segment (i.e., parent vessel) and a downstream segment (i.e., main vessel). This relationship should follow the law of conservation of mass and the law of conservation of momentum. The BLFM then uses this relationship as a junction condition. To obtain the junction conditions without collateral vessel geometry, the one-dimensional blood flow model combines these conservation laws with equation (2):

Wherein Q, P, D and A are flow, pressure, cross-sectional diameter, and cross-sectional area, respectively; subscripts i and i+1 represent the variables of the upstream and downstream segments, respectively; l _i is the length of segment i; (0) represents position z=0 (i.e., entrance); (L i) represents position z=l _i (i.e. the outlet of segment i); n _b is the number of bifurcation nodes.

In another embodiment of the present invention, the generating the fractional flow reserve of the target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow rate in step S140 may be further described in conjunction with the following description; wherein the target node is a specific process of a centerline node or a bifurcation node ".

Determining a stenosis corresponding to the target vessel segment based on the diameter of the target vessel segment, as described in the following steps; wherein the stenotic conditions include normal and stenosis;

Generating flow state data of the target node according to the stenosis condition, the one-dimensional blood flow model, the blood information and the inlet initial flow rate; wherein the flow state data includes a flow rate and a pressure of blood;

As an example, in the case where the target node is a centerline node, the present embodiment is a method of calculating the flow and pressure at the bifurcation node. The stenosis of the vessel segment where the vessel centerline node is located may be normal or stenotic, and thus there are two different ways of calculating the flow and pressure for the normal segment and the stenotic segment.

In one embodiment of the present invention, the generation of flow state data of the target node according to the stenosis, the one-dimensional blood flow model, the blood information, and the inlet initial flow rate may be further described in conjunction with the following description; wherein the flow state data includes the specific process of the flow rate and pressure of blood.

Determining a point parameter of an upstream segment node of the target node, the point parameter of the target node and the length of the target vessel segment according to the one-dimensional blood flow model when the stenosis of the target vessel segment is normal as described in the following steps;

As described in the following steps, flow state data of the target node is generated according to the blood information, the inlet initial flow, the point parameter of the upstream segment node, the point parameter of the target node, and the length of the target vessel segment.

As one example, BLFM calculates flow by leaking arteriole blood flow within a segment. The pressure field is then solved by a one-dimensional Navier-Stokes (N-S) equation. The one-dimensional N-S equation controls the flow regime within the segment. In the coronary arteries, the blood is assumed to be an incompressible newtonian fluid. In segments without stenosis, the flow may be assumed to be a poiseuille flow. In segment i without stenosis, the steady state control equation is for two adjacent centerline points Z _n and Z _n+1:

Wherein the last item is a friction item; z is the centerline axial coordinate; ρ and μ are the density and viscosity of blood, respectively.

In section i, equation (2) may give the ratio of the inlet flow Q i (0) and the outlet flow Q i (L i).

Wherein L _i is the length of segment i; (0) Representing position z=0 (i.e. inlet), (L i) representing position z=li (i.e. outlet of segment i); d is the cross-sectional diameter.

Then we assume that the collateral blood flow is evenly distributed along the segment. Thus, the flow at position z along the segment is:

the model then calculates the pressure along the line segment and equation (5) by equation (9).

In another embodiment of the present invention, the generation of flow state data of the target node from the stenosis, the one-dimensional blood flow model, the blood information, and the inlet initial flow rate may be further described in conjunction with the following description; wherein the flow state data includes the specific process of the flow rate and pressure of blood.

When the stenosis of the target vessel segment is a stenosis, determining a point parameter of an upstream segment node of the target node, the point parameter of the target node, and a stenosis length of the target vessel segment according to the one-dimensional blood flow model and the inlet initial flow, as described in the following steps;

And generating flow state data of the target node according to the blood information, the point parameter of the upstream segment node, the point parameter of the target node and the length of the narrow segment as follows.

As an example, in a segment s with a stenosis, poiseuille flow assumes that the pressure loss is underestimated. Thus, we use an empirical formula to calculate the pressure drop across the stenosis. The pressure drop Δp caused by stenosis is:

Wherein K _t =1.52; (0) represents position z=0 (i.e., entrance); (Z _s) represents position z=z _s (i.e. the narrowest place); l _s is the length of the stenosis.

The stenosis is detected by a stenosis detection filter. Arterioles in arterial segments are difficult to identify due to insufficient angiographic resolution. Thus, we use a leakage function to leak arteriole blood flow in the segment.

Experimental example

BLFM is a one-dimensional blood flow model used to calculate blood flow in the main coronary arteries. Compared with the prior art, the method has the advantages of higher efficiency and lower price for solving the FFR value. (experiments show that the solution of the FFR value by the one-dimensional blood flow model and the three-dimensional blood flow model is similar); second, BLFM can compensate for collateral blood flow at the actual bifurcation without the need to reconstruct the collateral blood flow structure. The problem of neglecting information of bifurcation positions in the prior art is solved, and the FFR value estimation is improved. Referring to fig. 3, which is a schematic diagram of FFR calculation results and pullback curves of a typical blood vessel, we calculated the ICA-FFR based on BLFM (FFR BLFM) in 123 individual blood vessels and compared with the true values and the existing four most advanced methods. The results show that the method can help to perform functional assessment on the coronary artery under the condition that the coronary pressure guide wire is not required to be introduced, and also proves the effectiveness of ICA-FFR based on BLFM and the competitive performance of the method with four most advanced methods, thereby having good clinical application value.

For the device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points.

Referring to fig. 4, there is shown a fractional flow reserve assessment device based on a flow model at a bifurcation site according to an embodiment of the present application, a coronary artery including a main vessel and a collateral vessel, a junction of the main vessel and the collateral vessel being a bifurcation node, and the target vessel being the main vessel;

the method specifically comprises the following steps:

An information acquisition module 410 for acquiring target coronary angiography information and blood information of a target coronary; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image;

A model construction module 420, configured to construct a corresponding one-dimensional blood flow model according to the target angiographic image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter;

an inlet condition module 430 for determining an inlet initial flow of the one-dimensional blood flow model from the target angiography sequence;

a flow calculation module 440 for generating a fractional flow reserve of the target node from the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or the bifurcation node.

In one embodiment of the present invention, the model building module 420 includes:

a central line sub-module, configured to determine a vessel central line corresponding to the target vessel according to the target angiography image; wherein the vessel centerline is comprised of a plurality of vessel centerline nodes and a plurality of bifurcation nodes;

The vessel reconstruction sub-module is used for reconstructing the target vessel according to the vessel center line to obtain the corresponding one-dimensional blood flow model;

the segmentation submodule is used for segmenting the one-dimensional blood flow model according to the bifurcation node to obtain a plurality of blood vessel segments;

A parameter sub-module, configured to determine a point parameter corresponding to the target node according to the target node and a vessel segment where the target node is located; wherein the point parameters include point coordinates, cross-sectional diameters and cross-sectional areas of the target nodes within the corresponding vessel segments.

In one embodiment of the present invention, the inlet condition module 430 includes:

An initial vessel segment sub-module for determining an initial vessel segment at the model inlet according to the one-dimensional blood flow model;

An initial segment length sub-module for determining an initial vessel segment length corresponding to the initial vessel segment according to the one-dimensional blood flow model;

An over-filling speed sub-module for generating an over-filling speed of the initial vessel segment in a resting state according to the initial vessel segment length and the target angiography sequence;

and the inlet flow sub-module is used for determining the inlet initial flow of the one-dimensional blood flow model according to the superfilling speed.

In one embodiment of the present invention, the blood information includes a density and a kinematic viscosity of blood, and the flow calculation module 440 includes:

The parameter calculation sub-module is used for determining the point parameter of the upstream segment node of the target node and the point parameter of the target node according to the one-dimensional blood flow model when the target node is a bifurcation node;

A first flow state sub-module, configured to generate flow state data of the target node according to the blood information, the inlet initial flow, the point parameter of the upstream segment node, and the point parameter of the target node; wherein the flow state data includes flow rate and pressure of blood flow; the formula is as follows:

And the first calculation sub-module is used for determining the corresponding fractional flow reserve according to the flow state data of the target node.

In another embodiment of the present invention, the blood information includes a density and a kinematic viscosity of blood, and the flow calculation module 440 includes:

The diameter calculation sub-module is used for determining the diameter of a target vessel segment corresponding to the target node according to the one-dimensional blood flow model when the target node is a vessel center line node;

A stenosis status sub-module for determining a stenosis status corresponding to the target vessel segment based on a diameter of the target vessel segment; wherein the stenotic conditions include normal and stenosis;

the second flow sub-module is used for generating flow state data of the target node according to the narrow condition, the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the flow state data includes a flow rate and a pressure of blood;

And the second calculation sub-module is used for determining the corresponding fractional flow reserve according to the flow state data of the target node.

In an embodiment of the present invention, the second flow submodule includes:

A normal unit configured to determine, when the stenosis of the target vessel segment is normal, a point parameter of an upstream segment node of the target node, a point parameter of the target node, and a length of the target vessel segment according to the one-dimensional blood flow model;

A non-narrow flow regime calculation unit for generating flow regime data of the target node according to the blood information, the inlet initial flow, the point parameter of the upstream segment node, the point parameter of the target node and the length of the target vessel segment: the formula is as follows:

In another embodiment of the present invention, the second flow submodule includes:

A stenosis unit configured to determine, when the stenosis of the target vessel segment is a stenosis, a point parameter of an upstream segment node of the target node, a point parameter of the target node, and a stenosis length of the target vessel segment according to the one-dimensional blood flow model and the inlet initial flow;

a narrow flow state calculating unit, configured to generate flow state data of the target node according to the blood information, the point parameter of the upstream segment node, the point parameter of the target node, and the length of the narrow segment; the formula is as follows:

Referring to fig. 5, a computer device for a fractional flow reserve assessment method of a flow model based on bifurcation site according to the present invention is shown, which may specifically include the following:

the computer device 12 described above is embodied in the form of a general purpose computing device, and the components of the computer device 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, a bus 18 that connects the various system components, including the system memory 28 and the processing units 16.

Bus 18 represents one or more of several types of bus 18 structures, including a memory bus 18 or memory controller, a peripheral bus 18, an accelerated graphics port, a processor, or a local bus 18 using any of a variety of bus 18 architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus 18, micro channel architecture (MAC) bus 18, enhanced ISA bus 18, video Electronics Standards Association (VESA) local bus 18, and Peripheral Component Interconnect (PCI) bus 18.

Computer device 12 typically includes a variety of computer system readable media. Such media can be any available media that is accessible by computer device 12 and includes both volatile and nonvolatile media, removable and non-removable media.

The system memory 28 may include computer system readable media in the form of volatile memory, such as Random Access Memory (RAM) 30 and/or cache memory 32. The computer device 12 may further include other removable/non-removable, volatile/nonvolatile computer storage media. By way of example only, storage system 34 may be used to read from or write to non-removable, nonvolatile magnetic media (commonly referred to as a "hard disk drive"). Although not shown in fig. 5, a magnetic disk drive for reading from and writing to a removable non-volatile magnetic disk (e.g., a "floppy disk"), and an optical disk drive for reading from or writing to a removable non-volatile optical disk such as a CD-ROM, DVD-ROM, or other optical media may be provided. In such cases, each drive may be coupled to bus 18 through one or more data medium interfaces. The memory may include at least one program product having a set (e.g., at least one) of program modules 42, the program modules 42 being configured to carry out the functions of embodiments of the invention.

A program/utility 40 having a set (at least one) of program modules 42 may be stored in, for example, a memory, such program modules 42 including, but not limited to, an operating system, one or more application programs, other program modules 42, and program data, each or some combination of which may include an implementation of a network environment. Program modules 42 generally perform the functions and/or methods of the embodiments described herein.

The computer device 12 may also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, camera, etc.), one or more devices that enable a user to interact with the computer device 12, and/or any devices (e.g., network card, modem, etc.) that enable the computer device 12 to communicate with one or more other computing devices. Such communication may occur through an input/output (I/O) interface 22. Moreover, computer device 12 may also communicate with one or more networks such as a Local Area Network (LAN), a Wide Area Network (WAN), and/or a public network such as the Internet, through network adapter 20. As shown in fig. 5, the network adapter 20 communicates with other modules of the computer device 12 via the bus 18. It should be appreciated that although not shown in fig. 5, other hardware and/or software modules may be used in connection with computer device 12, including, but not limited to: microcode, device drivers, redundant processing units 16, external disk drive arrays, RAID systems, tape drives, data backup storage systems 34, and the like.

The processing unit 16 executes various functional applications and data processing by running programs stored in the system memory 28, for example, to implement a fractional flow reserve assessment method based on a bifurcation site-based flow model provided by an embodiment of the present invention.

That is, the processing unit 16 realizes when executing the program: acquiring target coronary angiography information and blood information of a target coronary artery; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image; constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter; determining an inlet initial flow of the one-dimensional blood flow model according to the target angiography sequence; generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or the bifurcation node.

In an embodiment of the present application, the present application further provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements a fractional flow reserve evaluation method for a bifurcation position-based flow model as provided by all embodiments of the present application:

That is, the program is implemented when executed by a processor: acquiring target coronary angiography information and blood information of a target coronary artery; wherein the target angiographic information comprises a target angiographic image and a target angiographic sequence comprising the target angiographic image; constructing a corresponding one-dimensional blood flow model according to the target angiography image; wherein the one-dimensional blood flow model comprises a vessel centerline node parameter and a bifurcation node parameter; determining an inlet initial flow of the one-dimensional blood flow model according to the target angiography sequence; generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or the bifurcation node.

Any combination of one or more computer readable media may be employed. The computer readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer readable storage medium can be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, either in baseband or as part of a carrier wave. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Computer program code for carrying out operations of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, smalltalk, C ++ and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider). In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described by differences from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the scope of the embodiments of the application.

Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or terminal device that comprises the element.

The above detailed description of the fractional flow reserve assessment method and device based on the bifurcation position flow model provided by the application applies specific examples to illustrate the principles and embodiments of the application, and the above examples are only used to help understand the method and core idea of the application; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present application, the present description should not be construed as limiting the present application in view of the above.

Claims

1. A fractional flow reserve assessment method based on a flow model of a bifurcation site for calculating fractional flow reserve of a target node within a target vessel by invasive coronary angiography, the coronary artery comprising a main vessel and a collateral vessel, the junction of the main vessel and the collateral vessel being a bifurcation node, the target vessel being a main vessel, the method comprising:

2. The method of claim 1, wherein the constructing a corresponding one-dimensional blood flow model from the target angiographic image; wherein the one-dimensional blood flow model comprises a blood vessel center line node parameter and a bifurcation node parameter, and the method comprises the following steps:

3. The method of claim 2, wherein the step of determining the inlet initial flow of the one-dimensional blood flow model from the target angiography sequence comprises:

4. The method of claim 1, wherein the blood information comprises a density and a kinematic viscosity of blood, the generating a fractional flow reserve of a target node from the one-dimensional blood flow model, the blood information, and the inlet initial flow; the step of the target node being a center line node or a bifurcation node comprises the following steps:

Wherein Q, P, D and A are flow, pressure, cross-sectional diameter and cross-sectional area, respectively; the index a depends on the energy consumption; subscripts i and i+1 represent the variables of the upstream segment node and the downstream segment node, respectively; li is the length of segment i; (0) represents an entrance position z=0; (Li) represents the exit position z=li of segment i; n _b is the number of bifurcation nodes; ρ is the density of blood;

5. The method of claim 1, wherein the blood information comprises a density and a kinematic viscosity of blood, the generating a fractional flow reserve of a target node from the one-dimensional blood flow model, the blood information, and the inlet initial flow; the step of the target node being a center line node or a bifurcation node comprises the following steps:

6. The method of claim 5, wherein the generating flow state data for the target node is based on the stenosis, the one-dimensional blood flow model, the blood information, and the inlet initial flow rate; wherein the flow state data includes a flow rate and a pressure of blood, comprising:

wherein the last term of the first equation is a friction term; z is the axial coordinate of the centerline node; ρ and μ are the density and viscosity of blood, respectively; li is the length of segment i; (0) Representing the entrance position z=0, (Li) representing the exit position z=li of segment i; d is the cross-sectional diameter.

7. The method of claim 5, wherein the generating flow state data for the target node is based on the stenosis, the one-dimensional blood flow model, the blood information, and the inlet initial flow rate; wherein the flow state data includes a flow rate and a pressure of blood, comprising:

8. A fractional flow reserve evaluation device based on a flow model of a bifurcation site for calculating fractional flow reserve of a target node within a target vessel by invasive coronary angiography, the coronary artery comprising a main vessel and a collateral vessel, the junction of the main vessel and the collateral vessel being a bifurcation node, the target vessel being a main vessel, comprising:

A flow calculation module for generating a fractional flow reserve of a target node according to the one-dimensional blood flow model, the blood information and the inlet initial flow; wherein the target node is a vessel centerline node or the bifurcation node.

9. An apparatus comprising a processor, a memory, and a computer program stored on the memory and executable on the processor, the computer program, when executed by the processor, implementing the fractional flow reserve assessment method of a bifurcation site based flow model as claimed in any one of claims 1 to 7.

10. A computer-readable storage medium, on which a computer program is stored, which computer program, when being executed by a processor, implements the fractional flow reserve assessment method of a bifurcation site based flow model according to any of claims 1 to 7.