The Digital Modal Construction And Computational Fluid Dynamics Analysis Of External Illiac Artery Stenosis

Objective: With people's increasing concerns about health,the detection and diagnosis of lower limb ischemic disease ignored by people in the past have risen rapidly.It has become one of the diseases harmful to humans' health.Meanwhile,it is found that the age of patients who suffer this disease is gradually decreasing.Thus,the study of the occurrence and characteristics of this disease is very helpful for clinical treatment.The main purpose of this study is to establish the model of external artery stenosis close to the real state based on the relatively modern 256 rows MSCT and to make a better use of the new fluid dynamics software and model to analyze the dynamics features of blood in narrow blood vessel which is more real and cannot be detected by traditional equipment.Biomedical image processing technology and computational fluid dynamics are combined to explore the hemodynamic mechanism formed by iliac artery plaque.Methods: The four patients who have conducted the iliac artery CTA scanning in 2015 were selected for this experiment.According to the real data of external iliac artery stenosis scanned by CT which were stored in a CDRW in DICOM format,external iliac arteries of different parts were measured in PACS workstation,including lumen state before stenosis,of stenosis and after stenosis.Based on the 3D reconstruction technology of digital image processing,the DICOM documents output from PACS image were input into the MIMICS 14.0 software to model the external iliac artery stenosis blood vessel and establish the real vascular model of arteriostenosis.The 3D model data of artery generated by MIMICS 17.0 were input into the reverse engineering software,Geomagic 12.0,for optimization on the basis of the combination of 3D reconstruction technology and CFD technology to generate fedb files.The files then were input into Workbench 16.1 to establish fluid-structure interaction procedure to hypermesh and set the tube wall and blood respectively and conduct the coupling calculation and analysis to get the hemodynamic parameters of vascular model,such as the tube wall pressure,wall shear stress,velocity,Mises stress,vascular displacement and other parameters.Results:1 Having obtained the 3D finite element model of true external iliac artery.The vessel wall was set for the elastic blood vessels,which accords with the real arteries.The model established in this way can ensure the authenticity and accuracy of the data and helpful for us to conduct various fluid mechanics experiments.2 Having obtained the visual images of the parts of external iliac artery before stenosis and after stenosis.Then the fluid-solid coupling calculation were conducted to get a series of visual calculated fluid data.3 The flow velocity of blood became faster in narrow part and obviously caused the change of shear stress of the wall,which may be the reason for atherosclerosis.The flow velocity in external iliac artery before stenosis was slower than that after stenosis.The flow velocity in the stenosis part became faster,the pressure increased stepwise,and the shear stress increased stepwise,all of which would lead to increasing and falling off of plaque and intraplaque hemorrhage.4 The shear stress was maximum on the narrowest part of the left external iliac artery,less on the bifurcation of the abdominal aorta,and relatively small on the normal tube wall of abdominal aortic.It indicates that the shear stress plays an important role in hemodynamic changes of stenosis and vascular branch.Conclusions:1 Based on this test method,the data before and after stenosis of external illiac artery close to the real ones can be used to establish data model.The advantages includes convenient data collection,complete individualization,direct visual image,and multiplicating tests.2 A finite element model of external iliac artery stenosis was established.3 This test obtains various parameters of different parts of artery,the narrowest part of external illiac artery as well as vessels and blood fluid before and after stenosis,which accords with the current theories.The reliability and feasibility of the model construction by this method reveals that the simulation of the biomechanics of the external illiac artery close to the real ones are helpful for the prediction of the clinical conditions and formulation of the therapeutic regimen.