A non-invasive MRR calculation method based on computational fluid dynamics

Abstract

The present invention belongs to the technical field of coronary artery medicine, and discloses a non-invasive MRR calculation method based on computational fluid dynamics, including S1, reconstructing a three-dimensional model of the coronary artery and generating a mesh; S2, setting boundary conditions of the model; S3, simulating coronary artery blood flow for CFD and calculating the MRR value; The present invention calculates the MRR by a non-invasive method based on CFD, obtains the flow field and pressure field in the blood vessel by simulating the blood flow in the human blood vessel, and then calculates the MRR of the target blood vessel; This non-invasive method can significantly reduce the clinical examination cost and the risk of complications caused by invasive wire measurement, and it can also effectively evaluate the coronary microvascular function, which helps medical staff to formulate the best treatment plan.

Description

Technical Field

[0001] The present invention relates to the technical field of coronary artery medicine, and particularly to a non-invasive MRR calculation method based on computational fluid dynamics. Background Art

[0002] Coronary Microvascular Dysfunction (CMVD) is considered a potential cause of angina. Clinically, a reliable quantitative diagnosis method is needed to assist in formulating treatment plans for CMVD. Microvascular Resistance Reserve (MRR) is the ratio of the "true" microvascular resistance in the resting state to the microvascular resistance in the hyperemic state, indicating the maximum degree of decrease in microvascular resistance in the hyperemic state; moreover, the measurement result of MRR is not affected by heart rate, blood pressure, myocardial oxygen demand, or catheter position, and can accurately reflect the physiological function of the microcirculation. Therefore, CMVD can be predicted by calculating the value of MRR.

[0003] Currently, continuous thermodilution is used clinically to measure MRR. A wire with a pressure / temperature sensor is advanced into the distal part of the coronary artery, and room-temperature saline is continuously perfused at a fixed flow rate through a perfusion catheter in the proximal part of the coronary artery. The temperature data is measured by pulling back the wire according to the continuous thermodilution method to calculate the blood flow in the blood vessel. This method can measure the flow and pressure data in the resting state and hyperemic state by changing the perfusion flow rate; however, continuous thermodilution is an invasive method, which has high technical requirements for operators, brings physiological risks to patients, and in addition, brings high medical costs to patients. Summary of the Invention

[0004] The present invention aims to provide a non-invasive MRR calculation method based on computational fluid dynamics. The non-invasive method based on Computational Fluid Dynamics (CFD) calculates MRR by simulating the blood flow in the human blood vessels to obtain the flow field and pressure field in the blood vessel, and then calculates the MRR of the target blood vessel; this non-invasive method can significantly reduce the clinical examination cost and the risk of complications caused by invasive wire measurement, and it can also effectively evaluate the coronary microvascular function, which helps medical staff to formulate the best treatment plan.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A non-invasive MRR calculation method based on computational fluid dynamics, comprising the following steps:

[0007] S1. Reconstruct the three-dimensional coronary artery model and generate a mesh

[0008] Based on the coronary artery CTA image data, segment the coronary artery CTA image, extract the geometric information of the coronary artery from it, and reconstruct the three-dimensional coronary artery model. The reconstructed three-dimensional model includes the opening shapes of the coronary artery and its collateral vessels, excluding the aorta;

[0009] During the model construction process, trim the distal small blood vessels, smooth the reconstructed three-dimensional coronary artery model, and finally divide the three-dimensional model into tetrahedral meshes using the adaptive mesh method;

[0010] S2. Set the boundary conditions of the model

[0011] Set the inlet boundary condition of the model as the mean aortic pressure MAP, and the outlet boundary condition as the resistance R of each outlet of the model i ;

[0012] S3. Perform CFD for simulating coronary artery blood flow and calculate the MRR value

[0013] By adjusting the parameters, perform CFD simulations on the coronary artery blood flow in different states, and obtain the pressure distribution and flow distribution of the coronary artery under the resting state and the congestive state respectively; finally, calculate the MRR value of the target coronary artery.

[0014] Furthermore, in S1, use an automatic or semi-automatic segmentation algorithm to segment the coronary artery CTA image.

[0015] Furthermore, in S2, the method for setting the inlet boundary condition is as follows:

[0016] The mean aortic pressure MAP is the average blood pressure in the aorta during one cardiac cycle; calculate the mean aortic pressure MAP in the resting state based on the cuff pressure rest :

[0017] MAP rest = 0.4×(SBP - DBP)+DBP

[0018] In the formula, SBP and DBP are the systolic blood pressure and diastolic blood pressure respectively;

[0019] When performing the congestive state simulation, select the mean aortic pressure in the congestive state as the inlet boundary condition MAP hyp , which is obtained by converting the mean aortic pressure in the resting state:

[0020] MAP hyp = 1 / 1.1×MAP rest

[0021] The method for setting the outlet boundary condition is as follows:

[0022] Simulate the coronary artery pressure field and flow field under resting state and hyperemic state respectively. The specific steps are as follows:

[0023] A1. Segment the left ventricular volume of the diastolic and systolic CTA images, and obtain the left ventricular volumes of the diastolic and systolic phases as V diastole and V systole respectively. Among them, the average flow rate Q of the left ventricular outflow tract is:

[0024] Q = (V diastole - V systole )Hr

[0025] In the formula, Hr is the heart rate, the number of heart beats per minute;

[0026] A2. Allocate the coronary blood flow Q in = K × Q according to the types of left and right dominant coronary arteries. Determine the dominant type of coronary arteries through the reconstructed three-dimensional coronary artery model. Among them, the K value is determined as follows:

[0027] Blood flow proportion K Right coronary artery dominance Left coronary artery dominance or balance Left anterior descending artery 31.10％ 33.71％ Left circumflex artery 26.66％ 42.32％ Right coronary artery 41.85％ 21.00％

[0028] A3. Allocate the blood flow at each outlet of the coronary artery according to Murray's law. The blood flow Q out,i at the i-th outlet is:

[0029]

[0030] In the formula, D i is the average diameter near the i-th outlet, N is the total number of outlets, and β is a coefficient;

[0031] A4. Determine the resting state outlet resistance at the i-th outlet for simulating the outlet boundary condition of the intravascular dynamics in the resting state:

[0032]

[0033] In the formula, P v is the reference venous pressure, set to 5 mmHg;

[0034] A5. Set the hyperemic state outlet boundary condition as the hyperemic state outlet resistance at the i-th outlet and its expression is:

[0035]

[0036] In the formula, TCRI is the hyperemic factor, which is set individually according to the actual situation.

[0037] Further, in S3, the method for simulating coronary artery blood flow CFD is as follows:

[0038] Set the blood as Newtonian fluid, the blood vessel wall is rigid, and there is no slip on the blood vessel wall; by solving the incompressible Navier-Stokes equations; for the fluid domain Ω with the boundary Г, the velocity and pressure

[0039]

[0040]

[0041] where is the velocity field, is the pressure field, and t, μ, ρ are time, fluid viscosity, and fluid density respectively;

[0042] The method for calculating MRR is as follows:

[0043] Simulate the hemodynamics in the resting state and the hyperemic state respectively, and achieve this by changing the boundary conditions; the boundary condition Г of the fluid domain in the resting state rest is set to the mean aortic pressure MAP at the inlet in the resting state rest and the resistance at the outlet The boundary condition Г of the fluid domain in the hyperemic state hyp is set to the mean aortic pressure MAP at the inlet in the hyperemic state hyp and the resistance at the outlet After simulating the hemodynamics in the resting state and the hyperemic state respectively, obtain the pressure field and flow field of the blood flow in the coronary artery to calculate MRR:

[0044] MRR = (Q hyp / Q rest ) × (P a,rest / P d,hyp )

[0045] where Q hyp and Q rest are the coronary blood flows in the hyperemic state and the resting state respectively, and P a,rest is the coronary artery inlet pressure in the resting state, i.e., MAP rest , and P d,hyp is the pressure at the distal end of the diseased coronary artery in the hyperemic state.

[0046] The beneficial effects of the technical solution are:

[0047] 1. A non-invasive MRR calculation method based on computational fluid dynamics provided by the present invention only requires non-invasive imaging data to calculate MRR, avoiding invasive examinations, reducing treatment costs and the risk of clinical complications, and reducing the influence of operators on measurement results;

[0048] 2. A non-invasive MRR calculation method based on computational fluid dynamics provided by the present invention can obtain MRR values at various positions in the target coronary artery model through one calculation, accurately locating the diseased blood vessels in the region of microcirculation dysfunction;

[0049] 3. A non-invasive MRR calculation method based on computational fluid dynamics provided by the present invention can effectively evaluate the coronary microcirculation function, helping clinicians formulate the best treatment plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is the algorithm flowchart for determining boundary conditions and non-invasive calculation of MRR for a non-invasive MRR calculation method based on computational fluid dynamics of the present invention;

[0051] Figure 2 is a schematic diagram of segmenting the left ventricular volume of diastolic and systolic CTA images in S2 for a non-invasive MRR calculation method based on computational fluid dynamics of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The present invention will be further described in detail below with reference to the drawings and embodiments:

[0053] As Figure 1 shown, a non-invasive MRR calculation method based on computational fluid dynamics includes the following steps:

[0054] S1. Reconstruct the three-dimensional coronary artery model and generate a mesh

[0055] Based on coronary artery CTA image data, use an automatic or semi-automatic segmentation algorithm to segment the coronary artery CTA image, extract the geometric information of the coronary artery from it, and reconstruct the three-dimensional coronary artery model. The reconstructed three-dimensional model includes the opening shapes of the coronary artery and its collateral vessels, excluding the aorta;

[0056] During the model construction process, trim the distal small blood vessels, smooth the reconstructed three-dimensional coronary artery model, and finally divide the three-dimensional model into tetrahedral meshes using the adaptive mesh method;

[0057] S2. Set the boundary conditions of the model

[0058] Set the inlet boundary condition of the model as the mean aortic pressure MAP, and the outlet boundary condition as the resistance R at each outlet of the model i ;

[0059] Among them, the method for setting the inlet boundary condition is as follows:

[0060] The mean aortic pressure MAP is the average blood pressure in the aorta during one cardiac cycle; calculate the mean aortic pressure MAP in the resting state based on the cuff pressure rest :

[0061] MAP rest = 0.4×(SBP - DBP)+DBP

[0062] In the formula, SBP and DBP are the systolic blood pressure and diastolic blood pressure respectively;

[0063] When performing the simulation of the congested state, select the mean aortic pressure in the congested state as the inlet boundary condition MAP hyp , which is obtained by converting the mean aortic pressure in the resting state:

[0064] MAP hyp = 1 / 1.1×MAP rest

[0065] The method for setting the outlet boundary condition is as follows:

[0066] Respectively simulate the coronary artery pressure field and flow field in the resting state and the congested state. The specific steps are as follows:

[0067] A1. As Figure 2 shown, segment the left ventricular volume of the diastolic and systolic CTA images, and obtain the left ventricular volumes in the diastolic and systolic phases as V diastole and V systole ; among them, the average flow rate Q of the left ventricular outflow tract is:

[0068] Q = (V diastole - V systole )Hr

[0069] In the formula, Hr is the heart rate, the number of heartbeats per minute;

[0070] A2. Allocate the coronary artery blood flow Q according to the types of left and right dominant coronary arteries in = K×Q. Determine the types of coronary artery dominance through the reconstructed three-dimensional coronary artery model. Among them, the K value is determined as follows in the following table:

[0071] Blood flow proportion K Right coronary artery dominance Left coronary artery dominance or balance Left anterior descending artery 31.10％ 33.71％ Left circumflex artery 26.66％ 42.32％ Right coronary artery 41.85％ 21.00％

[0072] A3. Allocate the blood flow at each outlet of the coronary artery according to Murray's law. The blood flow Q out,i of the i-th outlet coronary artery is:

[0073]

[0074] Wherein, D i is the average diameter near the i-th outlet, N is the total number of outlets, and β is a coefficient;

[0075] A4. Determine the resting state outlet resistance of the i-th outlet Outlet boundary conditions for simulating the intravascular dynamics in the resting state:

[0076]

[0077] Wherein, P v is the reference venous pressure, set to 5 mmHg;

[0078] A5. Set the outlet boundary condition in the congested state to the congested state outlet resistance of the i-th outlet The expression is:

[0079]

[0080] Wherein, TCRI is the congestion factor, which is set personalized according to the actual situation;

[0081] S3. Perform CFD for simulating coronary artery blood flow and calculate the MRR value

[0082] By adjusting the parameters, perform CFD simulations on the coronary artery blood flow in different states to obtain the pressure distribution and flow distribution of the coronary artery in the resting state and the congested state respectively; finally, calculate the MRR value of the target coronary artery;

[0083] Among them, the method for simulating coronary artery blood flow by CFD is:

[0084] Set the blood as Newtonian fluid, the blood vessel wall is rigid, and there is no slip on the blood vessel wall; by solving the incompressible Navier-Stokes equation; for the fluid domain Ω with the boundary Г, solve to obtain the velocity and pressure

[0085]

[0086]

[0087] Wherein, is the velocity field, is the pressure field, and t, μ, ρ are time, fluid viscosity, and fluid density respectively;

[0088] The method for calculating MRR is:

[0089] Simulate the hemodynamics in the resting state and the hyperemic state respectively by changing the boundary conditions; the boundary condition Г of the fluid domain in the resting state rest is set to the mean aortic pressure MAP at the inlet in the resting state rest and the resistance at the outlet The boundary condition Г of the fluid domain in the hyperemic state hyp is set to the mean aortic pressure MAP at the inlet in the hyperemic state hyp and the resistance at the outlet After simulating the hemodynamics in the resting state and the hyperemic state respectively, obtain the pressure field and flow field of the blood flow in the coronary artery to calculate the MRR:

[0090] MRR = (Q hyp / Q rest ) × (P a,rest / P d,hyp )

[0091] In the formula, Q hyp and Q rest are the coronary blood flow in the hyperemic state and the resting state respectively, and P a,rest is the coronary artery inlet pressure in the resting state, that is, MAP rest , and P d,hyp is the pressure at the distal end of the diseased coronary artery in the hyperemic state.

[0092] The above are only the embodiments of the present invention, and common specific technical solutions or characteristics in the solutions are not described in detail here. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A non-invasive MRR calculation method based on computational fluid dynamics, characterized in that, Including the following steps: S1. Reconstruct the three-dimensional model of the coronary artery and generate a mesh Based on the coronary artery CTA image data, segment the coronary artery CTA image, extract the geometric information of the coronary artery from it, and reconstruct the three-dimensional model of the coronary artery. The reconstructed three-dimensional model includes the opening shapes of the coronary artery and its collateral vessels, excluding the aorta; During the model construction process, cut off the small distal vessels, smooth the reconstructed three-dimensional coronary artery model, and finally divide the three-dimensional model into tetrahedral meshes using the adaptive mesh method; S2. Set the boundary conditions of the model The inlet boundary condition of the model is set as the mean aortic pressure MAP, and the outlet boundary condition is set as the resistance R at each outlet of the model i ; Among them, the method for setting the inlet boundary condition is: The mean aortic pressure MAP is the average blood pressure in the aorta during one cardiac cycle; the mean aortic pressure MAP at rest is calculated based on the cuff pressure rest : MAP rest = 0.4 × (SBP - DBP) + DBP In the formula, SBP and DBP are the systolic blood pressure and diastolic blood pressure respectively; When simulating the congestive state, the mean aortic pressure in the congestive state is selected as the inlet boundary condition MAP hyp , which is obtained by converting the mean aortic pressure at rest: MAP hyp = 1 / 1.1 × MAP rest The method for setting the outlet boundary condition is: Simulate the coronary artery pressure field and flow field under the resting state and the hyperemic state respectively. The specific steps are: A1. Segment the left ventricular volume of the diastolic and systolic CTA images to obtain the left ventricular volumes at diastole and systole as V diastole and V systole ; where the average flow rate Q of the left ventricular outflow tract is: Q = (V diastole - V systole )Hr In the formula, Hr is the heart rate, the number of heartbeats per minute; A2. Allocate coronary blood flow Q according to the types of the left and right dominant coronary arteries in = K × Q. Determine the types of coronary artery dominance through the reconstructed three-dimensional coronary artery model. Among them, the determination of the K value is as follows: for the left anterior descending artery, the blood flow proportion K of the right coronary artery dominant type is 31.10%, and the blood flow proportion K of the left coronary artery dominant type or balanced type is 33.71%; for the left circumflex artery, the blood flow proportion K of the right coronary artery dominant type is 26.66%, and the blood flow proportion K of the left coronary artery dominant type or balanced type is 42.32%; for the right coronary artery, the blood flow proportion K of the right coronary artery dominant type is 41.85%, and the blood flow proportion K of the left coronary artery dominant type or balanced type is 21.00%; A3. Allocate the blood flow of each outlet of the coronary artery according to Murray's law. The blood flow Q of the coronary artery at the i-th outlet is out,i as follows: where D i is the average diameter near the i-th outlet, N is the total number of outlets, and β is a coefficient; A4. Determine the resting state outlet resistance of the i-th outlet Outlet boundary conditions for simulating the intravascular dynamics in the resting state: where P v is the reference venous pressure, assumed to be 5 mmHg; The boundary condition of the hyperemic state outlet is set to the hyperemic state outlet resistance of the i-th outlet The expression is as follows: In the formula, TCRI is the hyperemia factor, which is set personalized according to the actual situation; S3. Simulate the coronary artery blood flow for CFD and calculate the MRR value By adjusting the parameters, perform CFD simulations on the coronary artery blood flow in different states, and obtain the pressure distribution and flow distribution of the coronary artery under the resting state and the hyperemic state respectively; finally, calculate the MRR value of the target coronary artery.

2. The non-invasive MRR calculation method based on computational fluid dynamics according to claim 1, characterized in that In S1, use an automatic or semi-automatic segmentation algorithm to segment the coronary artery CTA image.

3. The non-invasive MRR calculation method based on computational fluid dynamics according to claim 1, wherein, In S3, the method for simulating the coronary artery blood flow CFD is: Assume that blood is a Newtonian fluid, the blood vessel wall is rigid, and there is no slip on the blood vessel wall; by solving the incompressible Navier-Stokes equations; for a fluid domain Ω with a boundary Г, the velocity and pressure In the formula, is the velocity field, is the pressure field, and t, μ, and ρ are time, fluid viscosity, and fluid density, respectively; The method for calculating the MRR is: The hemodynamics in the resting state and the hyperemic state are simulated respectively by changing the boundary conditions; the boundary condition Г of the fluid domain in the resting state rest is set as the mean aortic pressure MAP at the inlet in the resting state rest and the resistance at the outlet The boundary condition Г of the fluid domain in the hyperemic state hyp is set as the mean aortic pressure MAP at the inlet in the hyperemic state hyp and the resistance at the outlet After simulating the hemodynamics in the resting state and the hyperemic state respectively, the pressure field and the flow field of the blood flow in the coronary artery are obtained to calculate the MRR: MRR=(Q hyp / Q rest )×(P a,rest / P d,hyp ) Wherein, Q hyp and Q rest are the coronary blood flows in the hyperemic state and the resting state respectively, and P a,rest is the coronary artery inlet pressure in the resting state, i.e., MAP rest , and P d,hyp is the pressure at the distal end of the diseased coronary artery in the hyperemic state.

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