Method and system for obtaining coronary end microcirculation vascular resistance based on vascular growth

Abstract

The application relates to a method and system for obtaining coronary end microcirculation vascular resistance based on vascular growth, and the method comprises the following steps: acquiring medical images, and extracting a myocardial model and a coronary vascular model respectively; generating collateral vessels in the coronary vascular model; regarding all coronary vessels and collateral vessels as main vessels, and obtaining the position coordinates and the vascular radius; randomly selecting a point P in the myocardial model, connecting the point P with the outlet of the main vessel, and generating microcirculation vessels for each outlet of the main vessel; randomly selecting a point T in the point cloud file of the myocardial model, connecting the point T with the nearby microcirculation vessels, and generating multiple bifurcated microcirculation vessels, until the radius of all vessel outlets in the generated vascular tree is smaller than a preset vascular threshold; and calculating the resistance value of each outlet of the main vessel. Compared with the prior art, the coronary end microcirculation vascular resistance value calculated based on the reestablished microcirculation vascular model is more accurate and has the specificity of patients.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of blood vessel resistance acquisition, in particular to a coronary artery end microcirculation blood vessel resistance acquisition method and system based on blood vessel growth. BACKGROUND

[0002] The main cause of coronary heart disease is coronary stenosis caused by arteriosclerosis. The fractional flow reserve (FFR) refers to the ratio of the maximum blood flow that can be obtained by the myocardial region supplied by the coronary artery to the maximum blood flow that can be obtained by the same region under normal conditions. It can be simplified as the ratio of the average pressure (Pd) in the stenosis distal coronary artery to the average pressure (Pa) of the coronary artery orifice under the maximum myocardial hyperemia state. FFR can indicate the influence of coronary stenosis on the distal blood flow, and is used to assess whether the myocardium is ischemic. FFR has become a recognized indicator for functional evaluation of coronary stenosis.

[0003] When determining FFR, the blood flow velocity under the maximum myocardial hyperemia state and the average pressure of the coronary artery orifice are needed to calculate FFR by obtaining the average pressure in the stenosis distal coronary artery through different means. At present, the FFR acquisition method is mostly invasive, which has high risk and is expensive. In order to solve the above problems, researchers have proposed a non-invasive FFR measurement method combining coronary CTA and computational fluid dynamics (CFD);

[0004] A system and method for simulating and calculating fractional flow reserve by using computational fluid dynamics are disclosed in the invention with the publication number CN106650267B. The system includes: a blood vessel tree model generation module that obtains medical images, performs segmentation, and reconstructs the geometric model of the individual's blood vessel tree; a computational grid generation module that generates a computational grid for the geometric model and establishes a CFD model of the blood vessel tree; a boundary condition setting module that sets the corresponding inlet and outlet boundary conditions for the CFD model of the blood vessel tree; an attribute setting module that sets the physical properties of blood and the flow equation; a solver that solves the CFD model of the blood vessel tree based on the inlet and outlet boundary conditions, the set physical properties, and the flow equation to obtain the fluid parameters at each place in the blood vessel tree; and a post-processing module that post-processes the fluid parameters to obtain the fractional flow reserve. The inlet and outlet boundary conditions are both individual-specific.

[0005] The outlet boundary condition is the microvascular resistance at each outlet of the individual's blood vessel tree. Currently, the microvascular resistance is calculated by using a pressure guide wire with a temperature sensor to measure the relevant parameters and then obtain the coronary microvascular resistance index. However, this process requires the doctor to perform complex operations, which greatly increases the workload of the doctor.

[0006] To address this problem, invention publication number CN111627002A discloses a device and method for calculating the coronary microvascular resistance index. The coronary microvascular resistance index calculation device includes: an aortic pressure acquisition module for acquiring aortic pressure; a DSA image acquisition module for acquiring a coronary DSA image sequence; a curve generation module connected to the DSA image acquisition module for generating a contrast agent area change curve based on the imaging area of ​​the contrast agent in multiple target frames and the imaging time of the target frames; a curve slope acquisition module connected to the curve generation module for acquiring the average slope of the contrast agent area change curve; and a resistance index calculation module connected to the aortic pressure acquisition module and the curve slope acquisition module for calculating the coronary microvascular resistance index based on the aortic pressure and the average slope.

[0007] This method calculates the coronary microvascular resistance index by using the average slope of the contrast agent area change curve and aortic pressure. However, there are large measurement errors in both the acquisition of the contrast agent area and the measurement of aortic pressure. Furthermore, coronary microvessels are difficult to capture from coronary DSA image sequences, making it difficult to guarantee the accuracy of the acquired coronary microvessels and their resistance. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art in obtaining the accuracy of coronary microvessels and their resistance by providing a method and system for obtaining coronary terminal microcirculatory vascular resistance based on vascular growth.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A method for obtaining microcirculatory resistance at the distal coronary artery based on angiogenesis includes the following steps:

[0011] S1: Acquire medical images, extract and establish myocardial and coronary artery models respectively, divide the myocardial layer of the myocardial model into a mesh, and obtain the point cloud file of the myocardial model;

[0012] S2: Collateral vessels are generated upstream and downstream of each coronary artery in the coronary vessel model;

[0013] S3: Treat all the coronary arteries and collateral vessels as main vessels, and obtain the location coordinates of the exit of each main vessel and the vessel radius;

[0014] S4: Randomly select point P in the point cloud file of the myocardial model, pre-connect point P to the outlet of each main blood vessel, and select a segment of blood vessel from the pre-connection to generate a blood vessel based on the principle of minimizing the total volume of the microcirculatory blood vessels.

[0015] S5: repeating step S4 until a piece of microcirculation blood vessel is generated for each main body blood vessel outlet;

[0016] S6: randomly selecting a point T in the point cloud file of the myocardial model, screening m microcirculation blood vessels closest to the point T for pre-connection, for each pre-connected microcirculation blood vessel, selecting a point K to connect the point T, an upstream and a downstream in the microcirculation blood vessel respectively 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, newly generating branched multiple microcirculation blood vessels, and setting the blood vessel radius of each newly generated microcirculation blood vessel according to the area bifurcation power law rule; comparing the total volume of the blood vessel trees composed after all pre-connections, and retaining the pre-connection with the minimum total volume of the blood vessel tree, the blood vessel tree including coronary arteries, collateral vessels and microcirculation blood vessels;

[0017] S7: repeating step S6 until the radius of all blood vessel outlets in the generated blood vessel tree is less than a preset blood vessel threshold;

[0018] S8: calculating the resistance value of each outlet of the main body blood vessel according to the blood vessel tree obtained in step S7.

[0019] Further, in step S6, the blood vessel radius of each newly generated microcirculation blood vessel is set according to the area bifurcation power law rule, which is specifically:

[0020] The newly generated branched multiple microcirculation blood vessels include K-upstream blood vessels, K-downstream blood vessels and K-T blood vessels, the blood vessel radius of the K-upstream blood vessels is equal to the blood vessel radius of the main body blood vessel outlet, the blood vessel radius of the K-downstream blood vessels and the K-T blood vessels is equal, and the calculation expression of the blood vessel radius of the K-downstream blood vessels and the K-T blood vessels is:

[0021]

[0022] In the formula, R T is the blood vessel radius of the K-T blood vessel, R P is the blood vessel radius of the K-downstream blood vessel, and R i is the blood vessel radius of the K-upstream blood vessel, and γ is the bifurcation power law.

[0023] Further, 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 to select the point K is specifically:

[0024] According to the principle that the total pressure drop of each branch under the same main body blood vessel outlet is equal, the length and cross-sectional area of the blood vessels connected by the selected point K to the upstream and downstream in the microcirculation blood vessel are the same; according to the principle that the total volume of the microcirculation blood vessel is minimum, the selected point K satisfies the total volume of the blood vessels connected to the point T, the upstream and the downstream in the microcirculation blood vessel being minimum.

[0025] Further, the step S2 is specifically:

[0026] The increased number of collateral vessels, the vessel radius of each collateral vessel and the corresponding bifurcation power law are determined according to the vessel radius upstream and downstream of each coronary vessel in the coronary vessel model, and the increased collateral vessels are uniformly distributed upstream and downstream of the corresponding coronary vessel.

[0027] The relationship of the increased number of collateral vessels, the vessel radius of each collateral vessel and the corresponding bifurcation power law is:

[0028] Rh γ -Rd γ = n x R γ

[0029] In the formula, Rh is the upstream vessel radius of the coronary vessel, Rd is the downstream vessel radius of the coronary vessel, γ is the bifurcation power law, n is the number of collateral vessels, and R is the vessel radius of the collateral vessel.

[0030] Further, the method for obtaining the microcirculation vessel resistance of the coronary vessel end further comprises: obtaining the region of the heart cavity through the medical image, and if the pre-connected vessel passes through the region of the heart cavity in the pre-connection process in the steps S4 and S6, discarding the pre-connection.

[0031] Further, if the vessel radius of the generated microcirculation vessel is less than half of the vessel threshold in the step S6, the pre-connection condition of the corresponding microcirculation vessel is discarded.

[0032] Further, in the step S8, the resistance value of each outlet of the main vessel is specifically calculated as follows: the resistance of each microcirculation vessel is calculated based on the Poiseuille theorem, and then the resistance of each vessel outlet in the vessel tree is calculated according to the series-parallel connection rule, the resistance is equivalent to the resistance, and the calculation expression of the resistance of each microcirculation vessel is:

[0033]

[0034] In the formula, R is the resistance, μ is the blood viscosity, L is the vessel length, and A is the cross-sectional area of the vessel.

[0035] Further, in the step S8, the resistance value of each outlet of the main vessel is specifically calculated as:

[0036] The resistance of each vessel outlet in the vessel tree is determined by calculating the capacitance and / or inductance of each vessel, and the calculation expression of the capacitance of the vessel is:

[0037]

[0038] Wherein, C is the capacitance, A is the cross-sectional area of the blood vessel, L is the length of the blood vessel, p is the density of blood, and a is the pulse wave velocity.

[0039] The calculation expression of the inductance of the blood vessel is:

[0040]

[0041] Wherein, I is the inductance.

[0042] Further, the resistance of each blood vessel outlet in the blood vessel tree obtained in step S8 is used to set the outlet boundary condition of the three-dimensional CFD model of the blood vessel tree.

[0043] The application also provides a coronary artery end microcirculation blood vessel resistance acquisition system based on blood vessel growth, comprising a memory and a processor, the memory stores a computer program, and the processor calls the computer program to execute the steps of the method as described above.

[0044] Compared with the prior art, the application has the following advantages:

[0045] (1) The application considers that the myocardium and coronary blood vessels can be obtained through medical images such as CTA images, but the existing medical images are not accurate enough to clearly observe the collateral blood vessels and the coronary artery end microcirculation blood vessels, so the application regenerates the collateral blood vessels and the coronary artery end microcirculation blood vessels based on the myocardium and the coronary blood vessels according to the distribution law of the collateral blood vessels and the coronary artery end microcirculation blood vessels, thereby calculating the resistance of the coronary artery end microcirculation blood vessels, and the accuracy of the calculation result can be greatly improved.

[0046] (2) The radii of all blood vessel outlets in the blood vessel tree are generally less than a blood vessel threshold, and the reduction of the blood vessel radius is generally realized by bifurcation and according to the area bifurcation power law rule; to generate bifurcated blood vessels, the application first randomly selects a point P in the point cloud file of the myocardial model to connect with the outlet of the main blood vessel to generate microcirculation blood vessels; then randomly selects a point T to connect with the nearby microcirculation blood vessels to form a three-point combination of the upstream and downstream of the point T and a certain microcirculation blood vessel, according to the principle that the total pressure drops of each branch are equal, selects a point K to connect with the upstream and downstream of the point T and the certain microcirculation blood vessel, respectively, to form a plurality of bifurcated microcirculation blood vessels, and thus the coronary artery end microcirculation blood vessels obtained from the geometry and function are close to the real coronary microcirculation blood vessel distribution characteristics.

[0047] (3) Based on the patient-specific coronary trunk with added collateral vessels, the present invention determines the starting point of microcirculatory vessel growth and the initial cross-sectional area of ​​microcirculatory vessels. A coronary microcirculatory vessel model is generated inside the extracted myocardial model. The blood supply of the coronary artery to the myocardium is fully considered, so that the established microcirculatory vessel model is close to the real coronary microcirculatory vessel distribution characteristics in terms of geometry and function. The resistance value calculated based on the microcirculatory vessel model is more accurate and patient-specific. The numerical simulation model for calculating the fractional flow reserve has more accurate and patient-specific exit boundary conditions, thereby making the coronary FFR obtained by numerical simulation more accurate. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating a method for obtaining coronary artery terminal microcirculation vascular resistance based on angiogenesis, provided in an embodiment of the present invention.

[0049] Figure 2 This is a schematic diagram of a coronary artery, collateral vessels, and terminal microcirculatory vessels provided in an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of a coronary artery model provided in an embodiment of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0052] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0053] Example 1

[0054] like Figure 1 As shown, this embodiment provides a method for obtaining coronary artery terminal microcirculation vascular resistance based on angiogenesis, including the following steps:

[0055] S1: Acquire medical images, extract and establish myocardial and coronary artery models respectively, divide the myocardial layer of the myocardial model into a mesh, and obtain the point cloud file of the myocardial model;

[0056] S2: generating collateral vessels upstream and downstream of each coronary artery in the coronary vessel model;

[0057] The present application considers that myocardium and coronary vessels can be obtained through medical images such as CTA images, and the distribution of coronary vessels is as shown in Figure 3 However, the existing medical images are not accurate enough to clearly observe the collateral vessels and the coronary end microcirculation vessels, and therefore, the present application regenerates the collateral vessels and the coronary end microcirculation vessels based on the distribution rules of the collateral vessels and the coronary end microcirculation vessels and the myocardium and the coronary vessels, with the purpose of constructing the blood vessel distribution as shown in Figure 2 so as to calculate the resistance of the coronary end microcirculation vessels, which can greatly improve the accuracy of the calculation results.

[0058] Step S2 specifically includes:

[0059] The number of the increased collateral vessels, the vessel radius of each collateral vessel and the corresponding bifurcation power law are determined according to the vessel radius upstream and downstream of each coronary artery in the coronary vessel model, and the increased collateral vessels are uniformly distributed upstream and downstream of the corresponding coronary artery.

[0060] The relationship of the number of the increased collateral vessels, the vessel radius of each collateral vessel and the corresponding bifurcation power law is as follows:

[0061] Rh γ -Rd γ =n×R γ

[0062] In the formula, 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 vessel.

[0063] S3: regarding all the coronary arteries and collateral vessels as main vessels, obtaining the position coordinates and the vessel radius of the outlet of each main vessel;

[0064] S4: randomly selecting a point P in the point cloud file of the myocardium model, pre-connecting the point P with the outlets of the main vessels, and selecting a connection to generate a vessel from the pre-connection as a microcirculation vessel according to the principle of minimum total volume of the microcirculation vessels;

[0065] S5: repeating step S4 until a microcirculation vessel is generated for each outlet of the main vessels;

[0066] S6: randomly selecting a point T in the point cloud file of the myocardial model, screening m microcirculatory vessels closest to the point T for pre-connection, for each pre-connected microcirculatory vessel, selecting a point K to connect the point T, an upstream and a downstream in the microcirculatory vessel according to the principle that the total pressure drop of each branch under the same main vessel outlet is equal and the total volume of the microcirculatory vessel is minimum, then selecting to delete or not to delete the microcirculatory vessel, finally generating a plurality of branched microcirculatory vessels, and setting the vessel radius of each newly generated microcirculatory vessel in combination with the area bifurcation power law rule; comparing the total volume of the vessel trees composed after all pre-connections, retaining the pre-connection with the minimum total volume of the vessel tree, the vessel tree including the coronary artery, collateral vessels and microcirculatory vessels;

[0067] The principle that the total pressure drop of each branch under the same main vessel outlet is equal and the total volume of the microcirculatory vessel is minimum for selecting the point K is specifically:

[0068] According to the principle that the total pressure drop of each branch under the same main vessel outlet is equal, the length and cross-sectional area of the vessels connected by the selected point K to the upstream and downstream in the microcirculatory vessel are the same; according to the principle that the total volume of the microcirculatory vessel is minimum, the selected point K satisfies the total volume of the vessels connected to the point T, the upstream and the downstream in the microcirculatory vessel being minimum.

[0069] The principle that the total pressure drop of each branch under the same main vessel outlet is equal and the total volume of the microcirculatory vessel is minimum for selecting the point K is specifically:

[0070] The generated branched microcirculatory vessels include K-upstream vessels, K-downstream vessels and K-T vessels, the vessel radius of the K-upstream vessels is equal to the vessel radius of the main vessel outlet, the vessel radius of the K-downstream vessels and the K-T vessels is equal, and the calculation expression of the vessel radius of the K-downstream vessels and the K-T vessels is:

[0071]

[0072] In the formula, R T is the vessel radius of the 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 γ is the bifurcation power law.

[0073] S7: repeating step S6 until the radius of all vessel outlets in the generated vessel tree is less than a preset vessel threshold;

[0074] The radius of all the blood vessel outlets in the blood vessel tree is generally less than a blood vessel threshold, and the reduction of the blood vessel radius is generally achieved by bifurcation and according to an area bifurcation power law rule; to generate bifurcated blood vessels, the application first connects a point P selected randomly in a point cloud file of a myocardial model to a main body blood vessel outlet to generate microcirculation blood vessels; then connects a point T selected randomly to nearby microcirculation blood vessels to form a three-point combination of the point T, an upstream point and a downstream point in a certain microcirculation blood vessel, connects a point K selected according to the principle that the total pressure drops of each branch are equal to the point T, the upstream point and the downstream point in the certain microcirculation blood vessel to form a plurality of bifurcated microcirculation blood vessels, and thus the coronary artery end microcirculation blood vessels obtained are close to the real coronary artery microcirculation blood vessel distribution characteristics in terms of geometry and function. The blood vessels generated in the method are all assumed to be linear and have circular cross sections.

[0075] S8: Calculate the resistance values of each outlet of the main body blood vessels according to the blood vessel tree obtained in step S7.

[0076] In step S8, the resistance values of each outlet of the main body blood vessels are calculated as follows: the resistance of each microcirculation blood vessel is calculated based on the Poiseuille theorem, and then the resistance of each blood vessel outlet in the blood vessel tree is calculated according to the series-parallel connection rule. The resistance is equivalent to the resistance, and the calculation expression of the resistance of each microcirculation blood vessel is as follows:

[0077]

[0078] In the formula, R is the resistance, μ is the blood viscosity, L is the blood vessel length, and A is the cross-sectional area of the blood vessel.

[0079] In step S8, the method of steps S1-S7 can also be used to calculate the capacitance and / or inductance of the blood vessels, so as to calculate the resistance of each blood vessel outlet. The calculation of the resistance, capacitance and inductance of the blood vessel outlet has been disclosed in the prior art, and the application focuses on providing a specific calculation method of the resistance, capacitance and inductance of the blood vessel, which is more accurate.

[0080] The resistance values of each outlet of the main body blood vessels are calculated as follows:

[0081] The resistance of each blood vessel outlet in the blood vessel tree is determined by calculating the capacitance and / or inductance of each blood vessel, and the calculation expression of the capacitance of the blood vessel is as follows:

[0082]

[0083] In the formula, C is the capacitance, A is the cross-sectional area of the blood vessel, L is the blood vessel length, p is the blood density, and a is the pulse wave velocity.

[0084] The calculation expression of the inductance of the blood vessel is as follows:

[0085]

[0086] where I is an inductance.

[0087] The method for obtaining the end microcirculation vascular resistance of coronary artery further comprises: obtaining the region of the cardiac cavity through medical imaging, and discarding the pre-connection if the pre-connected blood vessel passes through the region of the cardiac cavity in the pre-connection process in step S4 and step S6.

[0088] If the generated vascular radius of the microcirculation blood vessel is less than half of the vascular threshold in step S6, the pre-connection condition corresponding to the microcirculation blood vessel is discarded.

[0089] The resistance of each blood vessel outlet in the vascular tree obtained in step S8 is used to set the outlet boundary condition of the three-dimensional CFD model of the vascular tree.

[0090] The method is based on the determination of the starting point of the microcirculation blood vessel growth and the initial cross-sectional area of the microcirculation blood vessel after the increase of the side branch blood vessels of the coronary artery trunk with patient specificity, generates the coronary microcirculation blood vessel model inside the extracted myocardial model, fully considers the blood supply condition of the coronary artery to the myocardium, makes the established microcirculation blood vessel model close to the real coronary microcirculation blood vessel distribution characteristics in geometry and function, makes the resistance value calculated based on the microcirculation blood vessel model more accurate and patient-specific, makes the numerical simulation model for calculating the flow reserve fraction have more accurate and patient-specific outlet boundary conditions, and thus makes the coronary FFR obtained by numerical simulation more accurate.

[0091] The embodiment also provides a system for obtaining the end microcirculation vascular resistance of coronary artery based on blood vessel growth, which comprises a memory and a processor, the memory stores a computer program, and the processor invokes the computer program to execute the steps of the method described above.

[0092] The specific implementation process of the method for obtaining the end microcirculation vascular resistance of coronary artery based on blood vessel growth described above in the embodiment is as follows:

[0093] (1) Obtain the myocardial model from the CTA image.

[0094] (2) Perform mesh division on the myocardial layer to obtain the point cloud file of the myocardium.

[0095] (3) Obtain the corresponding coronary blood vessel model from the CTA image.

[0096] (4) Determine the number n (1-7) of the increased side branch blood vessels, the radius R of each side branch, and the corresponding bifurcation power law γ (1.7-3) according to the upstream radius (Rh) and the downstream radius (Rd) of each coronary artery.

[0097] Rh γ -Rd γ = n x R γ

[0098] (5) The increased collateral vessels are evenly distributed between the upstream and downstream.

[0099] (6) The area and position coordinates of each coronary artery outlet (including the newly added collateral vessels) are obtained.

[0100] (7) The area of the cardiac cavity (i.e., the ventricular and atrial parts) is obtained from the CTA image.

[0101] (8) In the following angiogenesis process, when the radii of all outlet segment (terminal) vessels of the generated vascular tree model are less than a threshold r min (2 μm-10 μm), the generation of the entire coronary vascular model is completed.

[0102] (9) Randomly select a point P in the point cloud model of the myocardium as the outlet point of the generated vascular segment. Pre-connect the P point with each coronary artery outlet (area A i ) (directly discard the case of passing through the cavity), and the length of the obtained vessel is L i . Then, select the connection as a generated vascular segment (the area of the vascular segment is the area of the selected coronary artery outlet) by the principle of minimizing the total volume of the microcirculation vessels.

[0103] (10) Repeat step (9) until a vascular segment is generated for each outlet.

[0104] (11) Continue to randomly select a point T in the myocardial model, and pre-connect the m vessels closest to the point T (directly discard the case of passing through the cavity). According to the principle that the total pressure drop of each branch under the same coronary artery outlet is equal, and in combination with the area bifurcation power law rule, find the bifurcation point in the myocardium that minimizes the total volume of the vascular tree under this connection, complete the optimization of this connection, and take it as the preliminary connection result. Then, compare the total volumes of the vascular trees generated by all pre-connections, and take the minimum case as the final optimization result (if the radius of the microcirculation vessel in this connection is less than half of the threshold in (8), discard this case).

[0105] (12) Repeat step (11) until the termination condition in (8) is met.

[0106] (13) Calculate the resistance (resistor R) of each microcirculation vessel based on the Poiseuille theorem, and then calculate the equivalent resistance value of each coronary artery outlet based on the series-parallel connection rule of resistors. Calculate the compliance (capacitor C) and inertia (inductor I) of each microcirculation vessel by the following formula, and then calculate the equivalent capacitance and equivalent inductance of each coronary artery outlet based on the series-parallel connection rule. (A, L, μ, ρ, a represent the cross-sectional area of the vessel, the length of the vessel, the viscosity of the blood, the density of the blood, and the pulse wave velocity, respectively).

[0107]

[0108]

[0109]

[0110] The preferred embodiments of the present application have been described in detail above. It should be understood that modifications and variations to the preferred embodiments could be made by those skilled in the art in light of the teachings above without departing from the spirit of the present application. It is therefore contemplated that the application claim protection for such changes and modifications insofar as they come within the scope of the claims.

Claims

1. A method for obtaining coronary end microcirculation vascular resistance based on blood vessel growth, characterized in that, The method comprises the following steps: S1: acquiring medical images, extracting a myocardial model and a coronary vessel model respectively, performing mesh division on a myocardial layer of the myocardial model, and obtaining a point cloud file of the myocardial model; S2: generating collateral vessels upstream and downstream of each coronary vessel in the coronary vessel model; S3: regarding all the coronary vessels and collateral vessels as main vessels, acquiring position coordinates and vessel radii of outlets of each main vessel; S4: randomly selecting a point P in the point cloud file of the myocardial model, pre-connecting the point P with each main vessel outlet, and selecting a point K from the pre-connection to generate a blood vessel as a microcirculation vessel according to a principle of minimum total volume of microcirculation vessels; S5: repeating step S4 until a microcirculation vessel is generated for each main vessel outlet; S6: randomly selecting a point T in the point cloud file of the myocardial model, pre-connecting m microcirculation vessels closest to the point T, and selecting a point K to connect the point T, an upstream vessel and a downstream vessel in each pre-connected microcirculation vessel according to a principle of equal total pressure drop of branches under the same main vessel outlet and minimum total volume of microcirculation vessels, to generate branched microcirculation vessels, and setting vessel radii of the branched microcirculation vessels according to an area branching power law; comparing total volumes of vessel trees formed after all pre-connections, and retaining a pre-connection with minimum total volume of the vessel tree, wherein the vessel tree comprises the coronary vessels, the collateral vessels and the microcirculation vessels; S7: repeating step S6 until radii of all vessel outlets in the generated vessel tree are less than a preset vessel threshold; S8: calculating resistance values of each outlet of the main vessels according to the vessel tree obtained in step S7; Step S2 specifically comprises: determining the number of added collateral vessels, vessel radii of each collateral vessel and corresponding branching power law according to vessel radii upstream and downstream of each coronary vessel in the coronary vessel model, wherein the added collateral vessels are uniformly distributed upstream and downstream of the corresponding coronary vessels; a relationship formula of the number of added collateral vessels, vessel radii of each collateral vessel and corresponding branching power law is: wherein is the radius of the upstream vessel of the coronary artery, is the radius of the downstream vessel of the coronary artery, is the bifurcation power law, is the number of collateral vessels, is the vessel radius of the collateral vessels; in step S6, setting the vessel radii of each generated microcirculation vessel according to the area branching power law specifically comprises: the generated branched microcirculation vessels comprise K-upstream vessels, K-downstream vessels and K-T vessels, the vessel radius of the K-upstream vessel is equal to the vessel radius of the main vessel outlet, the vessel radii of the K-downstream vessel and the K-T vessel are equal, and a calculation expression of the vessel radii of the K-downstream vessel and the K-T vessel is: wherein is the vessel radius of the K-T vessel, is the vessel radius of the K-downstream vessel, is the vessel radius of the K-upstream vessel, is the bifurcation power law.

2. The method for obtaining the vascular resistance of the coronary microcirculation at the end of the coronary vessels based on the growth of blood vessels according to claim 1, characterized in that, selecting the point K according to the principle of equal total pressure drop of branches under the same main vessel outlet specifically comprises: according to the principle of equal total pressure drop of branches under the same main vessel outlet, the length and cross-sectional area of the vessels connected with the upstream and downstream of the microcirculation vessel are the same; and according to the principle of minimum total volume of microcirculation vessels, the selected point K satisfies the minimum total volume of the vessels connected with the point T, the upstream and downstream of the microcirculation vessel.

3. The method for obtaining the vascular resistance of the coronary microcirculation at the end of the coronary vessels based on the growth of blood vessels according to claim 1, characterized in that, The method further comprises: acquiring a region of a cavity of the heart, and if the pre-connected blood vessels pass through the region of the cavity of the heart, discarding the pre-connected blood vessels in the pre-connecting process in step S4 and step S6.

4. The method for obtaining the vascular resistance of the coronary microcirculation at the end of the coronary vessels based on the growth of blood vessels according to claim 1, characterized in that, If the radius of the generated microcirculation blood vessels is less than half of the threshold value in step S6, the pre-connected blood vessels corresponding to the microcirculation blood vessels are discarded.

5. The method for obtaining the vascular resistance of the coronary microcirculation at the end of the coronary vessels based on the growth of blood vessels according to claim 1, characterized in that, In step S8, the resistance value of each outlet of the main blood vessels is calculated as follows: the resistance of each microcirculation blood vessel is calculated based on Poiseuille's theorem, and then the resistance of each outlet of the blood vessel tree is calculated according to the series-parallel connection rule, the resistance is equivalent to the resistance, and the calculation expression of the resistance of each microcirculation blood vessel is: wherein is the electrical resistance, is the blood viscosity, is the blood vessel length, is the cross-sectional area of the blood vessel.

6. The method for obtaining the vascular resistance of the coronary microcirculation at the end of the coronary vessels based on the growth of blood vessels according to claim 1, characterized in that, In step S8, the resistance value of each outlet of the main blood vessels is calculated as follows: The resistance of each outlet of the blood vessel tree is determined by calculating the capacitance and / or inductance of each blood vessel, the calculation expression of the capacitance of the blood vessel is: wherein is the capacitance, is the cross-sectional area of the blood vessel, is the length of the blood vessel, is the density of the blood, is the pulse wave velocity; The calculation expression of the inductance of the blood vessel is: In the formulae, is an inductance.

7. The method for obtaining the vascular resistance of the coronary microcirculation at the end of the coronary vessels based on the growth of blood vessels according to claim 1, characterized in that, The resistance of each outlet of the blood vessel tree acquired in step S8 is used to set the outlet boundary condition of the three-dimensional CFD model of the blood vessel tree.

8. A system for obtaining coronary end microcirculation vascular resistance based on blood vessel growth, characterized in that, The computer program is stored in the memory and executed by the processor, and the steps of the method according to any one of claims 1 to 7 are executed. The computer program is stored in the memory and executed by the processor, and the steps of the method according to any one of claims 1 to 7 are executed.

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