The Study On The Scaling Law Of Coronaryartery Flow Division For FFR_CT

Fractional Flow Reserve（FFR）is the"gold standard"for clinical determination of functional myocardial ischemia,but its clinical application is limited due to defects such as invasive and high cost.The non-invasive Computed Tomography Angiography derived Fractional Flow Reserve(FFR_CT)of Coronary artery FFR can be achieved based on medical image technology and the computational fluid dynamics method.Coronary branch blood flow is the key boundary condition that affects the calculation accuracy of FFR_CT.By studying the same law of coronary artery morphological variables and blood flow in different individuals,namely the scaling law of coronary artery flow distribution,the most reasonable coronary flow distribution can be obtained,and higher precision FFR_CTcalculation can be achieved.Which branch of coronary artery flow diameter power law is more reasonable?Which scaling law of left and right coronary flow allocation can be used to calculate FFR_CTmore accurately?So there is no clear theory of coronary flow allocation.In order to calculate FFR_CTmore accurately,it has become a research hotspot to seek a reasonable power law of vascular flow-diameter in coronary branches and a scaling law of left and right coronary flow division.In this study,microcirculation resistance was estimated based on flow-diameter power laws with index values of 2.7 and 3.0,and FFR_CTwas simulated to solve the microcirculation resistance,and the differences between FFR_CTwere compared.By comparing the differences of FFR_CTbased on different left and right coronary flow allocation scaling laws,the coronary flow allocation theory of FFR_CTcan be solved and calculated more accurately.Specific research contents are as follows:Construction of geometric multi-scale coupling model for calculating FFR_CT.Based on the elastic cavity theory and geometrical parameters such as the length and cross-section area of each coronary vessel,the microcirculation resistance of each branch was estimated,and the personalized zero-dimensional model of each branch was determined.Then,the hemodynamics simulation of coronary artery was realized by combining with the three-dimensional anatomical model.The steps to construct the geometric multi-scale simulation model for calculating FFR_CTcan be described as follows:1)Create a patient-specific anatomical model based on coronary artery CTA data;2)Under the assumption that the supplying vessels are normal,the resting state blood flow and microcirculation resistance of the coronary branches are quantified to determine the personalized zero-dimensional model of each branch;3)Quantify the changes of microcirculation resistance of coronary artery branches under the condition of congestion.The geometric multiscale provides a research method and calculation basis for the study of the optimal personalized scaling law of coronary artery flow allocation.Study on the power law of flow-diameter of coronary artery branches.The flow division ratio of left and right coronary arteries was fixed at 6:4,and the flow of each coronary artery branch was distributed according to the flow-diameter power law with the index value of 2.7 and 3.0,respectively,to determine the coronary microcirculation resistance of each branch,and FFR_CTwas calculated by combining the geometric multi-scale simulation calculation method.According to the flow-diameter power law of different index values,the flow of each branch of coronary artery was allocated and the microcirculation resistance was estimated,and the differences of FFR_CTcalculated were compared and analyzed.FFR_CTresults of 70groups of 35 patients showed that the average difference of FFR_CTcalculated according to the flow-diameter power law of different index values for the same patient was about 0.004,showing no statistical difference.Study on the scaling law of left and right coronary artery flow division.A method to allocate the left and right coronary artery flow and estimate the microcirculation resistance according to the flow-section area power law is proposed,aiming at solving and calculating FFR_CTmore accurately.According to the flow-section area scaling law,the flow-volume power law of the mainstream and the fixed proportion,the left and right coronary flows were allocated and calculated to obtain FFR_CTrespectively.The differences between FFR_CTwere compared and analyzed.Fraction Flow Reservation（FFR）was used as the reference standard to evaluate its clinical diagnostic value.The results of 105 groups of FFR_CTof 35 patients showed that the maximum error of FFR_CTcalculated according to the flow-section area scaling law and clinical FFR was0.14,which was significantly lower than the two mainstream methods.For the same patient,the average relative errors of FFR_CTcalculated according to the flow-section area scaling law,the flow-volume power law of the mainstream and the fixed proportion distribution of left and right coronary flow were 4.37%,9.46%and 9.03%,respectively.Taking clinical FFR as the evaluation standard,the FFR_CTcalculation results of the three methods were compared,and it was found that FFR_CTcalculation was more effective according to the flow-section area scaling law.The accuracy,sensitivity,specificity,positive predictive value and negative predictive value were88.57%,66.70%,96.10%,85.70%and 89.30%,respectively.Clinical validation of the superiority of the scaling law of coronary artery flow division.Two patients with coronary stenosis were taken as the verification calculation objects.Under the condition that the left and right coronary artery flows were allocated according to the flow-section area scaling law,the coronary branch flows were allocated according to the flow-diameter power law of 2.7 and 3.0,and the microcirculation resistance was estimated.The microcirculation resistance of the two models was represented by and’,respectively.By analyzing the difference between and’,the phenomenon that the flow-diameter power law of coronary branches does not affect FFR_CTwas explained.The error between FFR_CTand clinical FFR was compared to verify that the method based on flow-section area scaling law could solve and calculate the conclusion of FFR_CTmore accurately.The calculation results showed that the maximum difference of microcirculation resistance of each coronary artery branch in patient 1 was 29.70936,and the FFR_CTand clinical FFR errors were 0.001 and 0.002,respectively.The extreme value of microcirculation resistance difference of each coronary artery branch in Patient 2 under congestion state was 500.1826,and the FFR_CTand clinical FFR errors were 0.002 and 0.003,respectively.The results of myocardial ischemia prediction were consistent with the clinical results.Based on geometry,the regular relationship between some personalized coronary artery morphological variables（diameter,cross-sectional area,coronary volume）and FFR_CTwas analyzed.A set of scaling law of coronary flow allocation which can be solved and calculated to obtain more accurate FFR_CTis described completely and clearly.The flow of coronary branch vessels is determined according to the flow-diameter power law with an index value of 2.7 or 3.0.The left and right coronary flow was distributed according to the flow-section area scaling law.The results of this study provide theoretical support for further research on the relationship between the physiological structure of coronary artery tree and the scaling law of flow division,and also lay the foundation for non-invasive numerical simulation research in the field of coronary artery in the future.