Thinner Regions of Intracranial Aneurysm Wall Correlate with Regions of Higher Wall Shear Stress: A 7T MRI Study

Schematic overview of the algorithm to determine the apparent wall thickness and its correlation to wall shear stress in intracranial aneurysms on 7T MR imaging. Blocks represent in- and outputs, and arrows represent procedures within the algorithm. The numbers in the boxes refer to the visualizations of several steps at the bottom of the image: 1) MPIR-TSE image (transverse orientation); the red box indicates the area of brain tissue that is used for the correction (by fitting a second-order polynomial function to the brain tissue intensities) and normalization of the vessel wall intensities; 2) cropped MPIR-TSE image clearly showing the aneurysm wall and its varying intensity; 3) the PC/mag image used for segmentation of the aneurysm lumen; 4) cropped PC/mag image; 5) registered images: pink is MPIR-TSE; green, PC/mag; 6) 3D shell encompassing the aneurysm wall; 7) brain tissue mask; 8) overlay of the 3D shell on the MPIR-TSE image with tissue mask; 9) segmented aneurysm wall; and 10) radial intensity profiles to sample vessel wall intensities (ie, signal maxima within the 3D shell, indicated by red dots). The profiles were rotated by stepping with 1°; here only a few profiles are shown. The images are taken from aneurysm 1 (Table). PC/P indicates phase-contrast MRI phase images.

Visual comparison between apparent wall thickness and wall shear stress in intracranial aneurysms on 7T MR imaging. 3D color map with AWT (left images) and 3D color map with WSS (right images) are shown. The color scaling for all AWT images is equal, while the WSS images were individually scaled as indicated by the color scale bars. Parent vessels and wall areas where no AWT data (N.D.) were available are displayed in gray. Numbers correspond to the numbering of the aneurysms in the Table. The other side of the aneurysms is shown in the On-line Figure.