Hemodynamics Analysis Of Local Carotid Artery Plaques And Implication To Plaques

Background:Atherosclerosis is a serious disease threat to human health, which is associatedwith smoking，hyperlipidemia, hypertension, etc. To find and clear these factors of thedisease is important in early diagnosis and intervention. The formation ofatherosclerosis is a complex process.Atherosclerosis plaques show preferentiallocalization of thecertain regions, such as branches, bifurcations or curves, whichcharacterized as complex spatial and temporal hemodynamic changes. It is suggestedthat hemodynamics play an important role in the development ofarteriosclerosis.Hemodynamics parameters, such as wall pressure(WP), wall shear stress(WSS),cannot be measured in vivo. Thus, computational fluid dynamics(CFD) has beenestablished to be an important method to study hemodynamics disturbances. However,most previous studies hadused phantoms or idealism geometry models undersimplified presumptions. With the development of CFD and medical imagingtechniques, now we are able to get more accurate patient-specific geometry and flowdata to investigate the hemodynamics mechanism of atherosclerosis formation andprogression.Objectives:The aim of the study was to investigate the hemodynamics of in vivo carotidartery using computational dynamics (CFD) and magnetic resonance angiography(MRA). Analyze the relationship between hemodynamics changes and atherosclerosisformation and progression.Methods:(1) Acquire DICOM (Digital Imaging and Communications in Medicine) formatimage data from patients who has received carotid magnetic resonanceangiography. These patients were divided into normal group andstenosedgroup. (2) Import the DICOM format image data into MIMICS software and reconstructpatient-specific threeDimensional (3D) carotid artery models.(3) Import the3D carotid artery models into ANSYS software. Apply the ANSYSsoftware for post-processing—ICEM(Integrated Computer Engineering andManufacturing) to create infinite element grids.(4) Hemodynamics parameters were obtained with a finite volume method byFLUENT software.(5) Use the post-processing module of ANSYS software to obtainvisualizedpictures of parameter distributions.Results:(1) Blood flow in normal straight artery was laminar, turbulence flow with lowvelocity occurred at the outer walls of bifurcation. However, velocity in localstenosis artery was fast.(2) The distributions of wall pressure(WP) were uneven around bifurcations: theapices of bifurcation showed high WP while the outer walls of bifurcationshowed low WP. WP appeared lower in stenosed region.(3) The apices of bifurcation showed high WSS while the outer walls ofbifurcation showed low WSS. However, high WSS were observed in stenosedregion.Conclusion:(1) Changes of flow velocity and the appearance of turbulence flow are related toatherosclerosis.(2) Low WSS is related to the formation of atherosclerosis.(3) High velocity、Low WP and high WSS are related to the rupture ofatherosclerosis plaques.(4) MRA-based CFD provides an effective method to obtain accurate visualizedhemodynamics parameters.