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Fig 4. Example of a long-segment high-grade stenosis (string sign) identified on CTA, which appeared occluded on MR imaging/MRA. A and B, Curved planar reformatted images of the left ICA demonstrate flamelike tapering of the proximal vessel with wall thickening and long-segment high-grade stenosis (arrow). C, Axial plane from CTA shows the tiny residual lumen of the vessel (arrow). D, Contrast-enhanced MRA acquired on the same day demonstrates apparent occlusion just distal to the carotid bifurcation (arrow). E, T1-weighted fat-suppressed axial image demonstrates methemoglobin in the left ICA wall. F and G, Axial source images from 2D time-of-flight MR angiography show the T1 shinethrough of the methemoglobin, but the absence of flow-related enhancement in the left distal cervical ICA.
