The Relationship Between Intracranial Vascular Wall Shear Force And Atherosclerosis: A Computational Fluid Dynamics Study

Background and purpose-Low wall shear stress?WSS?has been found strongly related to coronary and carotid artery atherosclerosis formation.Using 3-dimentional?3D?T1 high-resolution magnetic resonance imaging?HRMRI?and computational fluid dynamic?CFD?,we aimed to explore the correlation between local WSS and middle cerebral artery?MCA?atherosclerosis.Methods-We retrospectively analyzed the 3D T1 HRMRI data of 43 patients with low grade stenotic?<50%?MCA atherosclerosis and 25 individuals with normal MCAs.Vessel walls of each MCA was divided into superior,inferior,ventral or dorsal sides,while each plaque location was also categorized as proximal segment,mid-segment,and distal segment.Based on the curvature of horizontal segment of MCA,we categorized the 4 vessel walls into inner wall and outer wall of curvature.3D reconstructed WSS model was built by CFD technique.Coregistration between 3D T1 HRMRI and 3D reconstructed WSS model was done with the same coordinates,so that the location of plaque can be correctly identified while calculating WSS.The relationships between WSS at each side of the vessel walls and plaque locations were compared and analyzed.Results-A total of 94 plaques and 50 normal MCAs were studied.In the control group,the WSS of ventral wall?61.1 ±22.8 dyne/cm2?is significantly lower than those of the inferior?69.5 + 26.6 dyne/cm2?,dorsal?80.8±27.9dyne/cm2?and superior wall?74.9±26.3 dyne/cm2;P=0.002?at the proximal segment of MCA.The WSS of the ventral wall?69.0±26.8 dyne/cm2?and inferior wall?53.4±19.3 dyne/cm2?are significantly lower than those of the dorsal wall?88.4±27.9 dyne/cm2?and superior wall at the mid-Ml segment?88.8±26.4 dyne/cm2;P<0₀01?;WSS of the inner wall?63.1±20.8 dyne/cm2?is distinctively lower than that of the outer wall?82.4±24.6 dyne/cm2;P<0.001?.In the patient group,the WSS of plaque involved vessel walls is significantly lower than that of the uninvolved walls regardless of the location of the plaques at the proximal segment of MCA?60.9 + 19.6 dyne/cm2vs.74.8 ± 23.9 dyne/cm2,P=0.001?,mid-segment?60.5±28.1 dyne/cm2vs.93.5±38.4 dyne/cm2,P<0.001?,and distal segment?53.4±27.0 dyne/cm2vs.93.3±44.1 dyne/cm2 P<0.001?.Of the total 52 plaque lesions at the mid-segment,49 plaques located at the inner walls of MCA curvature.WSS of the plaque involved inner wall is significantly lower than that of the uninvolved outer wall?59.0±24.5 dyne/cm2 vs.95.2±40.7 dyne/cm2;P<0.001?.No significant differences were found between WSS of plaque involved wall in patient group and WSS of the same vessel wall of concordant location in control group.Conclusions-The WSS was naturally unevenly distributed along MCA wall.Early stage MCA plaques tend to locate at the lower WSS zones with specific patterns.Further studies are required to investigate the clinical value of individual WSS analysis on MCA atherosclerosis prevention and treatment.