Assessment Of Arterial Vascular Function Via Computational Fluid Dynamic Mechanics Based On Digital Medical Images

Background:The thrombotic ischaemic dysfunction caused by vascular lesions often leads to irreversible and severe consequences.Therefore,the study of blood vessels has always been a hot issue in the medical community.The development of medical imaging technology has greatly improved the accuracy and sensitivity of the discovery and diagnosis of vascular diseases,but relying solely on medical imaging techniques tends to easily overestimate the severity of the condition and thus use unnecessary interventional therapies.Clinically,in addition to medical imaging technology,directly measured hemodynamic related indicators are considered as the gold standard for auxiliary diagnosis.For example,indicators of the perfusion are used to evaluate brain tissue lesions,fractional flow reserve is used to assess coronary lesions,flow rates measured by interventions,and so on.However,these methods often cause secondary damage,or the operation is complicated and the economic cost is high.Objective:In recent years,with the popularization of computational fluid dynamics in the human blood vessel field,hemodynamic parameters have been widely proposed for the evaluation of vascular lesions.In particular,wall shear stress is considered an indispensable risk factor for the development of atherosclerosis.This study aims to provide a potential and effective tool for the assessment of arterial function based on mature medical imaging technology combined with computational fluid technology.Material and Methods:Reconstructed three dimensional blood structures based on digital medical images,such as MRA,CTA and DSA.The next step is solving the Navier-Stokes equations with the help of boundary conditions.The pressure guide-wire measured pressure and UDV measured velocity are employed as validation.Besides,comparison assessment of different boundary conditions was delivered to explore the best boundary condition.In addition,we proposed an index for quantifying the carotid arterial supply function.Results:We found that vascular bifurcation,different degrees of stenosis and curvatures affect the distribution of hemodynamic parameters.Moreover,when the geometrical characteristics co-occur,the impact is far greater than the effect of their individual appearance,which explains why the lesions are prone to appear in complex structures such as bifurcations and bends.When studying the effect of different CFD boundary conditions configuration on the distribution of hemodynamic parameters in blood vessels,we found that the Womersley analytical solution can describe the blood flow status in the normal blood vessel segment approximately,but for the diseased blood vessels,boundary conditions based on the clinical measurement data(speed,pressure,etc.)are more reliable.For the evaluation of three different outlet boundary conditions,we find that the Windkessel model is in the best fit with the clinical measurement results,but the longest calculation time;the fully develop flow model can get the results in shortest time,but it is not stable enough when compared with the other two methods;while the structured-tree model can get similar accuracy with the Windkessel model,it only consumes half the computing time of the Windkessel model.In addition,the quantitative function evaluation index based on computational fluid dynamics proposed by us is also in good agreement with the perfusion result.Conclusions:Computational fluid dynamics technology combined with digital medical images can be used to reconstruct blood flow in blood vessels,which providing more intuitive results to assist clinical diagnosis.It can also provide some important index hardly to be measured in clinical directly,such as wall shear stress,that is great helpful in arterial functional assessment.