Computer Simulation Of Stanford B Aortic Dissection On MRA

Objective:This study used magnetic resonance angiography(MRA)images to establish the morphological models of Stanford B aortic dissection(AD)to verify the accuracy of the models.And the study used computer simulation software to perform the numerical simulation of the morphological models,exploring the feasibility of computer simulation research for individualized Stanford B AD based on MRA images.Methods:(1)10 patients of Stanford B AD who underwent MRA were enrolled.The morphological models of AD were established based on their MRA images.The AD’s morphological parameters(the diameter of aortic sinuses of Valsalva,sinotubular junction,mid ascending aorta,proximal aortic arch,mid aortic arch,proximal descending thoracic aorta,mid thoracic descending aorta,aorta at diaphragm,abdominal aorta at the celiac axis origin in corresponding long diameter of true lumen,short diameter of true lumen,long diameter of false lumen,short diameter of false lumen,tear size and location of dissection involved site)were measured on MRA images and reconstructed morphological model respectively.Exploring the morphology differences on AD between the MRA images and the morphological model reconstructed based on MRA images.(2)After optimization and meshing,the above 10 morphological models were imported into FLUENT software for numerical simulation,and the results were imported into CFD post software for post-processing to obtain the wall shear stress distribution diagram of AD,the wall pressure distribution diagram of AD,the streamline diagram of blood flow and the distribution diagram of blood flow velocity at different moments in a cardiac cycle.(This paper took case 7 as an example).Results:(1)The morphological parameters of AD varied greatly(the diameter of AD,tear size and location of dissection involved site).The coefficient of variation ranged from 0.084 to 0.555.(2)There was no significant difference between the original MRA image and the reconstructed AD morphological model on the morphological parameters(P>0.05).(3)Distribution of wall shear stress:the distribution of wall shear stress was more uniform in the early stage of ejection,only slightly higher in the true lumen of AD(proximal descending thoracic aorta and mid thoracic descending aorta).In the peak period of ejection,higher wall shear stress also appeared near the tear(proximal descending thoracic aorta),and the increase of wall shear stress was more obvious in the true lumen of AD(mid thoracic descending aorta).In the slow ejection phase,the wall shear stress distribution became uneven,and a higher wall shear stress appeared in the false lumen near the tear.In the early,middle and late filling stage,the distribution of shear stress changed little,and the shear stress decreased slowly.(4)Distribution of blood vessel wall pressure:in the early stage of ejection and peak period of ejection,the wall pressure distribution of AD gradually decreased from near to far,and the maximum wall pressure was located at the opening of ascending aorta.The distribution of wall pressure gradually increased from near to far in the slow ejection phase and filling phase,and the maximum wall pressure was located at the distal end of aorta and the pressure distribution became uneven.(5)Distribution of blood flow streamlines:the blood flow streamlines were evenly distributed in the early stage of ejection,with little turbulence and eddy current;at the peak stage of ejection,the streamlines near the tear began to become disordered.In the slow ejection phase and the filling phase,the streamline became more disordered.The turbulent part of the streamline was mainly concentrated in the false lumen,while the streamline of the true lumen was relatively uniform.(6)Distribution of blood flow velocity:in the early stage of ejection,the velocity distribution was uniform,and there was a faster velocity at the tear,and the velocity in the true lumen was slightly faster than that in the false lumen.In the peak period of ejection,the velocity distribution was uniform,the direction of blood flow was consistent,the overall velocity increased,and a faster velocity appeared in the true lumen of the mid thoracic descending aorta.In the slow ejection phase and filling phase,the flow velocity gradually decreased,and multiple eddies could be seen in the true lumen and false lumen.Conclusions:(1)The morphological parameters of different AD are diverse,so the establishment of individual AD morphological model is helpful for individual computer simulation.(2)Based on MRA images,an accurate morphological model of AD can be established.(3)Based on the MRA image of AD,an individual computer simulation model of AD can be established.(4)The computer simulation of AD based on MRA can obtain the wall shear stress distribution diagram of AD,the wall pressure distribution diagram of AD,the streamline diagram of blood flow and the distribution diagram of blood flow velocity at different times in the cardiac cycle,which is helpful for the study of AD and clinical individualized diagnosis and treatment.