Arjen Lindenholz

63 The Use and Pitfalls of Intracranial Vessel Wall Imaging 3 Figure 5. (A and B) 3T pre- (A) and postcontrast (B) T 1 -weighted vessel wall images (voxel size 0.5 x 0.5 x 1.0 mm 3 ) of a 40-year-old female with a recent right-sided ischemic stroke, zoomed in on the cavernous sinus. The postcontrast image of the cavernous sinus shows diffuse contrast enhancement of the cavernous plexus (white arrows) which makes delineation of the carotid vessel wall challenging. (C and D) 7T postcontrast T 1 - weightedMPIR-TSE images of the same subject, zoomed in on the vertebral arteries that cross the dura mater. In transverse orientation (C) , contrast enhancement (white arrows) of both vertebral arteries can be seen when crossing the dura mater. In sagittal orientation (D) this enhancement can be better appreciated (white arrow) at the same location of the transdural crossing of the vertebral arteries. Common artifacts & corresponding pitfalls Like all MRI examinations, vessel wall MRI is sensitive to motion artifacts, even more so because of the relatively long acquisition times. Also, SENSE (SENSitivity Encoding) fold-over artifacts need to be considered when deciding to use a vessel wall MRI sequence with SENSE acceleration. Next to these more general artifacts, there are two artifacts that may pose an interpretation problem specifically when assessing vessel wall MRI images. The first is the slow-flow artifact ( Figure 6 ). Due to the parabolic flow velocity profile within a vessel, the flow directly next to the vessel wall is slower compared with the center of the lumen. Intracranial vessel wall MRI sequences that use the inflow or outflow of blood to suppress the arterial lumen can therefore show a higher signal from unsuppressed blood