Computer Simulation Of Abdominal Aortic Aneurysm Based On MRA

Objective:On the basis of verification the accuracy of morphological model of abdominal aortic aneurysm(AAA)based on magnetic resonance angiography(MRA),to explore the feasibility of individualized AAA computer simulation based on MRA.Methods:(1)10 AAA patients' MRA images were collected.The morphological model of AAA was established based on their MRA images by using reverse modeling method.The AAA's morphological parameters[(transverse diameter of proximal aneurysm neck(TDPAN),length of proximal aneurysm neck(LPAN),transverse diameter of aneurysm inlet(TDAI),length of aneurysm(LA),the largest transverse diameter of aneurysm(LTDA),transverse diameter of aneurysm outlet(TDAO),(transverse diameter at the abdominal aorta bifurcates(TDAAB),diameter of right common iliac artery(DRCIA),diameter of left common iliac artery(DLCIA),distortion angle of proximal aneurysm neck(DAPAN),distortion angle of aneurysm(DAA)and angle of abdominal aorta bifurcates(AAAB)]were measured on MRA images and reconstructed morphological model respectively.Exploring the morphology differences on AAA between the MRA images and the morphological model reconstructed based on MRA images(2)The morphological model of the above 10 AAA cases was established based on MRA images.After building and optimizing mesh model,numerical simulation was performed in real geometries by finite element analysis software.The convergent data were imported into CFD-post software for analysis,outputting the streamline diagram of blood flow,distribution diagram of blood flow velocity,wall shear stress distribution diagram of AAA and wall pressure distribution diagram of AAA at different moments in a cardiac cycle(This paper took one of the patients as an example).Results:(1)The morphological parameters of AAAs varied greatly.(2)There was no significant difference between the original MRA image and the reconstructed AAA morphological model on the morphological parameters(TDPAN,LPAN,TDAI,LA,LTDA,TDAO,TDAAB,DRCIA,DLCIA,DAPAN,DAA and AAAB)(P>0.05).(3)Streamline of blood flow:Laminar flow is primary blood flow pattern in AAA's neck,and eddy flow and turbulent flow are mainly blood flow in AAA's lumen,especially in the dilated region of AAA.(4)Blood flow velocity distribution:The blood flow velocity changed with the cardiac cycle,and the blood flow velocity in the ejection phase was significantly faster than that in the filling phase.The blood flow velocity in the AAA's neck fluctuated obviously and was faster than that in the AAA's lumen.It reached the maximum value when the time of peak ejection(t=0.08s).The blood flow velocity of most region of the AAA's lumen was low throughout the cardiac cycle and hardly fluctuated.The high flow velocity region in AAA's lumen mostly located in where the inlet blood flow continues directly.(5)Wall shear stress distribution:The magnitude of wall shear stress changed with the change of blood flow velocity,and the relationship between them was positively correlated generally.The magnitude and variation of wall shear stress in ejection period were greater than those in filling period.The wall shear stress on the AAA's neck was higher than AAA's lumen throughout the cardiac cycle,and the latter doesn't fluctuate much.(6)Wall pressure distribution:The wall pressure varies with the flow velocity,and the relationship between them was positively correlated generally.The wall pressure of the AAA's body and its distribution maximized when the time of peak ejection(t=0.08s).The wall pressure and its change range in the accelerated ejection period were larger than those in the decelerated ejection period and filling period.Conclusions:(1)Establishment of individualized AAA morphological model is helpful to the establishment of individualized computer simulation model because the shape and size of different AAA are diverse.(2)MRA has the advantages of no ionizing radiation and no iodine allergic reaction,etc.The AAA morphological model can be accurately established based on MRA images.(3)The individualized AAA computer simulation model can be established based on MRA image.(4)AAA computer simulation based on MRA images can obtain the streamline diagram of blood flow,distribution diagram of blood flow velocity,wall shear stress distribution diagram of AAA and wall pressure distribution diagram of AAA at different moments in the cardiac cycle,which is of help for AAA's research and clinical individualized diagnosis and treatment.