Arjen Lindenholz

57 The Use and Pitfalls of Intracranial Vessel Wall Imaging 3 The patient’s treatment status is another important clinical feature for vessel wall MRI assessment. For instance, when a patient with cerebral vasculitis is treatedwith prednisolone, it is important to know when treatment has commenced relative to the time of the imaging examination: vessel wall enhancement may be lower or have disappeared altogether. Also, in case of an ischemic infarct that has been treated with thrombolysis or intra-arterial treatment, there may be local vessel wall enhancement present at the location of the previous occlusion. 54,55 Finally, if a patient has undergone an MRI examination including contrast administration less than 12 hours before vessel wall MRI, there may be residual contrast enhancement on the subsequent ‘precontrast’ vessel wall images. Common indications At our institution, the most common indication for our 3T vessel wall MRI protocol is a suspected cerebral vasculitis (either primary angiitis of the central nervous system or due to other causes). When this suspicion is raised by the clinician, a spectrum of symptoms is often present that can also indicate the presence of other vascular diseases, like small vessel disease or large artery atherosclerosis with unstable plaques. Vessel wall MRI can assist in differentiating between these vascular diseases but may also be helpful during follow-up and evaluation of the received treatment. Other vascular diseases in which vessel wall MRI may be indicated are the detection or evaluation (evolution) of large artery atherosclerosis with or without arterial remodeling, and less frequently moyamoya vasculopathy, dissections and cerebral aneurysms (all mostly for research purposes). When 3T vessel wall MRI does not show any abnormalities, when the clinician suspects subtle vessel wall disease, or when all arteries of the circle of Willis need to be thoroughly assessed and/or screened, our 7T protocol can be considered if this platform is available. Systematic approach of vessel wall assessment General assessment Vessel wall MRI assessment at our institution is generally performed on specialized workstations for diagnostic imaging, with a high-resolution monitor and using a PACS (picture archiving and communication system, IDS7, Sectra AB, Linköping, Sweden). When an intracranial arterial stenosis has been found, at TOF-MRA, vessel wall MRI could entail a dedicated characterization of this lesion on vessel wall images. 8 In practice, this is a less common situation in our patient population, so we perform a complete search of the large intracranial vasculature, starting at the extracranial internal carotid and vertebral artery and then following the course of these arteries into the basilar artery and anterior, middle and posterior cerebral artery branches, including the M1, (very) proximal M2, A1, (very) proximal