Figure 4.

Intracranial atherosclerosis. (a) Axial TOF MRA demonstrates segmental high-grade stenosis of the left M1 MCA segment (large arrow), due to ICAD. (b) Minimal flow-related enhancement seen on the axial source image is not well seen on the 3D MIP reconstruction, appearing as an occlusion (small arrow). The contralateral side demonstrates normal MCA caliber. An absent left intracranial VA was also incidentally noted, a benign variant. Of note, subsequent VWI confirmed diagnosis of ICAD (not shown). (c) 3D MIP TOF-MRA reconstruction from a different patient demonstrates multifocal ICAD, e.g. at the proximal A1 and distal M1 segments (arrowheads). A fetal origin of the right PCA was also incidentally noted (curved arrow). MIP, maximum intensity projection; ICAD, intracranial atherosclerotic disease; MCA, middle cerebral artery; MRA, MR angiography; PCA, posterior cerebral artery; VWI, vessel wall MR imaging; TOF, time-of-flight.