Coronary plaque biomechanical property calculation method

Abstract

The invention discloses a coronary plaque biomechanical property calculation method, and belongs to the field of computational biofluid mechanics in biomedical engineering. According to the method, the influence of cardiac pulsation, coronary blood vessel complex geometric distribution characteristics and coronary plaque composition factors is integrally considered, and the coronary plaque biomechanical characteristics are calculated; wherein the number of the fluid computational domains is two, and the two fluid computational domains are respectively a coronary vessel intracavity blood flow area and a plaque tissue fluid flow area surrounded by a fibrous membrane and a blood vessel; the two structural computational domains are respectively an elastic blood vessel wall and an ultrathin flexible plaque fiber membrane; the plaque fiber membrane generates deformation movement under the pressure of blood in blood vessels on two sides and tissue fluid in the plaque; the motion of the coronary plaque fibrous membrane is described by adopting an independently researched and developed immersion film method, and compared with a traditional coronary plaque biomechanical characteristic calculation method, the method has better information integrity, better accuracy and wider applicability.

Description

Technical Field

[0001] This invention relates to the field of computational biofluid dynamics, and in particular to the calculation of the biomechanical properties of coronary artery plaques based on fluid-structure interaction theory. Background Technology

[0002] While significant progress has been made in the study of the occurrence, development, and rupture mechanisms of coronary atherosclerotic plaques, there is still a considerable distance to go before fully elucidating these mechanisms. The presence of coronary atherosclerotic plaques narrows the coronary artery lumen, thereby leading to myocardial ischemia.

[0003] From a mechanical perspective, the formation, development, and rupture of coronary atherosclerotic plaques are the result of long-term interactions between cardiac pulsation, coronary artery structure, blood flow, vessel wall, and plaque, accompanied by the coupling effects of myocardial motion, blood viscosity, and changes in the geometry, structure, and material properties of the vessel wall and plaque. Current research on the fluid-structure interaction (FSI) of coronary atherosclerotic plaque wall stress and blood flow mainly suffers from the following four problems: ① Failure to consider the influence of coronary artery structure. Simplifying the inflow and outflow conditions of local arteries containing plaques in FSI studies results in the loss of blood flow characteristic information; ② Failure to consider the influence of myocardial pulsation. Ignoring the changes in coronary artery structure shape caused by myocardial pulsation severely affects blood flow patterns and plaque stress analysis; ③ Failure to consider the hyperelastic effects of vessels and plaques. Assuming blood is an incompressible fluid, the rigidity of the vessel and plaque walls allows blood pressure propagation to be unrestricted by vessel wall flexibility, leading to errors in the assessment of blood pressure and wall shear stress; ④ Simplification of the influence of plaque structure. Simplifying the three-dimensional plaque geometry or using a two-dimensional plaque structure will affect the analysis of plaque stress, especially the assessment of stress at the fibrous cap. These issues mean that biomechanical factors obtained by fluid-structure interaction methods cannot accurately describe the mechanical properties of the plaque, thus affecting the objective evaluation of endothelial cell function and plaque rupture. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a method for calculating the biomechanical properties of coronary plaques. This method comprehensively considers the effects of cardiac pulsation, the complex geometric distribution of coronary vessels, and the compositional factors of coronary plaques to calculate their biomechanical properties. The method includes two fluid computational domains: the blood flow region within the coronary lumen and the flow region of tissue fluid within the plaque surrounded by the fibrous membrane and blood vessel. It also includes two structural computational domains: the elastic vessel wall and the ultrathin, flexible plaque fibrous membrane. The plaque fibrous membrane undergoes deformation and movement due to the pressure of blood within the vessels on both sides and tissue fluid within the plaque. A self-developed immersion membrane method is used to describe the movement of the coronary plaque fibrous membrane. Compared with traditional methods for calculating the biomechanical properties of coronary plaques, this method offers better information integrity, higher accuracy, and wider applicability.

[0005] To achieve the above-mentioned invention, the technical solution adopted by the present invention is: a method for calculating the biomechanical properties of coronary plaques, the method including coronary artery and plaque information acquisition, coronary blood and plaque tissue fluid and fluid-structure interaction analysis of vessel wall and plaque fibrous membrane structure, and plaque vulnerability assessment. Coronary artery and plaque information acquisition: The patient's cardiac pulsation images and the three-dimensional spatial geometric morphology data of the vascular cavity enclosed by the coronary arteries are obtained through coronary CTA technology; the geometric distribution of internal components of the plaque is obtained through CT technology; and a structural and fluid geometric model of cardiac pulsation data and coronary plaque vascular fluid-structure interaction analysis is established based on the above medical images. Fluid-structure interaction analysis of coronary blood and plaque tissue fluid and vessel wall and plaque fibrous membrane structure. There are two fluid computational domains: the blood flow region in the coronary lumen and the plaque tissue fluid flow region surrounded by the fibrous membrane and vessel. There are two structural computational domains: the elastic vessel wall and the ultrathin flexible plaque fibrous membrane. The plaque fibrous membrane undergoes deformation motion due to the movement of blood and plaque tissue fluid on both sides. Fluid-structure interaction analysis of patchy fiber membranes was performed using the immersion film method; specifically, the immersion film method is as follows: 1) The patchy fiber membrane is described using a spatially discrete triangular mesh with thickness; 2) The computational domains of blood and plaque tissue fluid on both sides of the plaque fibrous membrane are discretized using tetrahedral meshes; 3) After discretization, the computational domain of the plaque fibrous membrane, which is immersed in blood and tissue fluid, intersects with the computational domain of blood and plaque tissue fluid, forming a truncation; 4) Two pairs of real and virtual nodes are generated at the blood boundary of the fibrous cap and the tissue fluid boundary of the fibrous cap plaque. The values ​​of the virtual nodes are obtained by interpolating the physical quantities of the real nodes and the physical quantities at the membrane position according to the variable gradient and the position vector. Then, the fluid computational domain boundary velocity on both sides of the fibrous membrane is obtained, and then the liquid pressure distribution at the boundary is obtained by the governing equation. Patch vulnerability assessment: Describe the motion deformation and stress load distribution information of the patch fiber membrane to conduct patch vulnerability assessment.

[0006] Furthermore, when conducting fluid-structure interaction analysis of the vessel wall and plaque fibrous membrane, the loads on both sides of the plaque fibrous membrane include the loads of coronary blood movement and plaque tissue fluid movement, which are obtained based on the influence of cardiac pulsation, the complex geometric distribution characteristics of coronary vessels, and the compositional factors of coronary plaques.

[0007] Furthermore, the impact of cardiac pulsation is divided into the acquisition and use of cardiac pulsation data. Through CT medical images of multiple cardiac pulsation cycles of patients, the overall geometric data of the myocardium is extracted, and statistical regression is used to form a mathematical formula to describe the pulsation pattern of the myocardium within a cycle. Then, it is matched with the numerical simulation calculation time to obtain the displacement and velocity of the myocardium at the connection point between the myocardium and the coronary artery at the numerical simulation time. The connection point between the myocardium and the coronary artery is a grid node of the coronary artery sidewall. The displacement and velocity of cardiac pulsation are imposed at this node, so that the calculation system introduces periodic cardiac pulsation action.

[0008] Furthermore, the complex geometric distribution characteristics of coronary vessels are characterized by the geometric distribution of plaque formation locations near the bifurcation of coronary vessels. Considering the geometry of the upstream bifurcation coronary arteries, numerical calculations are used to accurately describe the upstream flow distribution of plaques.

[0009] Furthermore, the composition of the plaque affects the movement of fluid within the plaque, and mathematical equations are used to simulate and calculate the movement of tissue fluid in the plaque.

[0010] The beneficial effects of this invention are as follows: This method comprehensively considers the effects of cardiac pulsation, the complex geometric distribution characteristics of coronary arteries, and the compositional factors of coronary plaques to calculate the biomechanical properties of coronary plaques. Specifically, there are two fluid computational domains: the blood flow region within the coronary lumen and the flow region of tissue fluid within the plaque surrounded by the fibrous membrane and blood vessel. There are also two structural computational domains: the elastic vessel wall and the ultra-thin, flexible plaque fibrous membrane. The plaque fibrous membrane undergoes deformation and movement due to the pressure of blood within the vessels on both sides and tissue fluid within the plaque. The immersion membrane method is used to describe the movement of the coronary plaque fibrous membrane. Compared with traditional methods for calculating the biomechanical properties of coronary plaques, this method has better information integrity, higher accuracy, and wider applicability. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the workflow of a method for calculating the biomechanical properties of coronary plaques.

[0012] Figure 2 This is a schematic diagram of the overall structure of the coronary arteries of the heart.

[0013] Figure 3 This is a schematic diagram of the independent structure of the coronary artery system.

[0014] Figure 4 yes Figure 3 A magnified schematic diagram of the dashed area A in the middle left coronary artery (including the left anterior descending branch and the left circumflex branch).

[0015] Figure 5 This is a schematic diagram of a calculation example considering the presence of plaques within the coronary arteries.

[0016] Figure 6This is a schematic diagram illustrating a case study of how the fibrous membrane is used to separate blood from plaque tissue fluid using a membrane immersion method.

[0017] In the diagram: 1. Myocardium, 2. Heart, 3. Aorta, 4. Left main coronary artery, 5. Left circumflex artery, 6. Left anterior descending artery, 7. Diagonal branch, 8. Right coronary artery, 9. Fibrous membrane, 10. Lipid core, 11. Intima, 12. Media, 13. Direction of blood flow, 14. Inlet of the vessel, 15. Outlet of the vessel, 16. Elastically deformable coronary artery wall, 17. Inelastically deformable coronary artery wall, 18. Displacement of the vessel wall, 19. Atherosclerotic plaque. Detailed Implementation

[0018] in accordance with Figure 1 This is a flowchart of a method for calculating the biomechanical properties of coronary plaques.

[0019] The coronary information acquisition module acquires the patient's heart pulses (e.g., through coronary CTA and CT techniques) Figure 2 As shown), the three-dimensional spatial geometry of the vascular cavity enclosed by the coronary arteries (e.g.) Figure 3 , 4 (As shown) data, geometric distribution of components within the plaque (e.g.) Figure 5 (As shown); forming a fluid computational domain and a structural computational domain; The coronary blood-plaque tissue fluid and vessel wall-plaque fibrous membrane structure fluid-structure interaction analysis module creates a computational domain for coronary blood flow analysis. Figure 5 For example, the blood flow analysis calculation domain consists of a region enclosed by an inelastic coronary artery wall 17, an elastic coronary artery wall 16, a coronary vessel inlet 14, a vessel outlet 15, and a fibrous cap 9; the plaque tissue fluid flow analysis calculation domain, with... Figure 5 For example, the region is composed of the fibrous membrane 9 and the media 12; the structural analysis objects include the elastically deformable coronary artery wall 16 and the fibrous membrane 9.

[0020] The pressure of fluids on both sides of the coronary plaque fibrous membrane was calculated using the immersion membrane method. (Reference) Figure 6In the diagram, the thick black solid line represents the fibrous membrane, with the blood computational domain and plaque computational domain on either side of the fibrous membrane, respectively. The plaque fibrous membrane is immersed in the blood and tissue fluid computational domains and intersects with them, forming a physical truncation. Two pairs of real and virtual nodes are generated at the blood boundary and the plaque tissue fluid boundary of the fibrous membrane. Taking edge I1 (connected by nodes a2 and a6) as an example, the fibrous membrane, represented by the thick solid line, truncates edge I1. For the blood flow computational domain, node a6 is located in the plaque tissue fluid, and this node becomes a virtual node, named g26. Similarly, node a2 is located in the blood region, and for the tissue fluid computational domain, this node becomes a virtual point g62. Thus, when the blood flow field calculation requires the physical information of node a6, it is provided by the virtual node g26. Its value is obtained by interpolating the physical quantities of the real node a2 and the physical quantities at the membrane position based on the variable gradient and position vector. The calculation process for edge I2 (connected by nodes a2 and a7) is similar. In this way, the fluid velocity on both sides of the fiber membrane can be obtained through this method, and then the liquid pressure distribution at the boundary can be obtained through the governing equations. The calculated fluid load is applied to the structure, the deformation and stress of the fiber membrane are calculated, and the physical position of the fiber membrane is updated according to the displacement to achieve the purpose of simulating structural motion. This process is repeated to form a fluid-structure interaction calculation process. The patch vulnerability judgment module uses the deformation and stress of the hardened patch fiber membrane obtained through the above process to draw the three-dimensional wall shear stress distribution of the fiber membrane and to perform patch vulnerability judgment.

[0021] The described cases (such as) Figure 5 and Figure 6 These are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this invention are within the scope of protection of this invention.

Claims

1. A method for calculating the biomechanical properties of coronary plaques, characterized in that, This method includes acquiring coronary artery and plaque information, analyzing the fluid-structure interaction between coronary blood and plaque tissue fluid and the vascular wall and plaque fibrous membrane structure, and determining plaque vulnerability. Coronary artery and plaque information acquisition: The patient's cardiac pulsation images and the three-dimensional spatial geometric morphology data of the vascular cavity enclosed by the coronary arteries are obtained through coronary CTA technology; the geometric distribution of internal components of the plaque is obtained through CT technology; and a structural and fluid geometric model of cardiac pulsation data and coronary plaque vascular fluid-structure interaction analysis is established based on the above medical images. Fluid-structure interaction analysis of coronary blood and plaque tissue fluid and vessel wall and plaque fibrous membrane structure. There are two fluid computational domains: the blood flow region in the coronary lumen and the plaque tissue fluid flow region surrounded by the fibrous membrane and vessel. There are two structural computational domains: the elastic vessel wall and the ultrathin flexible plaque fibrous membrane. The plaque fibrous membrane undergoes deformation motion due to the movement of blood and plaque tissue fluid on both sides. Fluid-structure interaction analysis of patchy fiber membranes was performed using the immersion film method; specifically, the immersion film method is as follows: 1) The patchy fiber membrane is described using a spatially discrete triangular mesh with thickness; 2) The computational domains of blood and plaque tissue fluid on both sides of the plaque fibrous membrane are discretized using tetrahedral meshes; 3) After discretization, the computational domain of the plaque fibrous membrane, which is immersed in blood and tissue fluid, intersects with the computational domain of blood and plaque tissue fluid, forming a truncation; 4) Two pairs of real and virtual nodes are generated at the blood boundary of the fibrous cap and the tissue fluid boundary of the fibrous cap plaque. The values ​​of the virtual nodes are obtained by interpolating the physical quantities of the real nodes and the physical quantities at the membrane position according to the variable gradient and the position vector. Then, the fluid computational domain boundary velocity on both sides of the fibrous membrane is obtained, and then the liquid pressure distribution at the boundary is obtained by the governing equation. Patch vulnerability assessment: Describe the motion deformation and stress load distribution information of the patch fiber membrane to conduct patch vulnerability assessment.

2. The method according to claim 1, characterized in that, When performing fluid-structure interaction analysis of the vessel wall and plaque fibrous membrane, this method considers the loads on both sides of the plaque fibrous membrane as including the loads of coronary blood movement and plaque tissue fluid movement, which are derived based on the influence of cardiac pulsation, the complex geometric distribution characteristics of coronary vessels, and the compositional factors of coronary plaques.

3. The method according to claim 2, characterized in that: The impact of cardiac pulsation is divided into the acquisition and use of cardiac pulsation data. Through CT medical images of multiple cardiac pulsation cycles of patients, the overall geometric data of the myocardium is extracted, and statistical regression is used to form a mathematical formula to describe the pulsation pattern of the myocardium within a cycle. Then, it is matched with the numerical simulation calculation time to obtain the displacement and velocity of the myocardium at the connection between the myocardium and the coronary artery at the numerical simulation time. The connection between the myocardium and the coronary artery is a grid node of the coronary artery sidewall. The displacement and velocity of cardiac pulsation are imposed at this node, so that the calculation system introduces periodic cardiac pulsation action.

4. The method according to claim 3, characterized in that: The complex geometric distribution characteristics of coronary vessels are characterized by the geometric distribution of plaque formation locations near the bifurcation of coronary vessels. Considering the geometry of the upstream bifurcation coronary arteries, numerical calculations are used to accurately describe the upstream flow distribution of plaques.

5. The method according to claim 4, characterized in that: The composition of plaques affects the movement of fluid within the plaque, and mathematical equations are used to simulate and calculate the movement of tissue fluid in plaques.

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