In recent years, multiple intracranial vessel wall MRI sequences have been developed for direct evaluation of the intracranial vessel wall and its pathology in vivo.¹ These studies have mainly been performed on 3 and 7 tesla (T) field strengths. Current challenges at 3T are incomplete suppression of cerebrospinal fluid (CSF) which may hamper vessel wall assessment, and limited coverage of most intracranial vessel sequences. 7T MRI has the advantage of an increased signal-to-noise ratio (SNR), allowing for complete suppression of CSF and whole-brain imaging within clinically feasible scan times, but is hampered by restricted accessibility and magnetic field inhomogeneity causing artefacts that may impair vessel wall assessment. In the current study, we compared 3T and 7T MRI for visualizing both healthy intracranial arterial vessel wall as well as possible vessel wall lesions.Twenty-one healthy volunteers (12 male; age 66 ± 5 years) without a history of cerebrovascular or ischemic heart disease were included. All subjects were scanned at 3T MRI (Philips Healthcare) with a 3D T1-weighted volumetric isotropic reconstructed turbo spin-echo acquisition (VIRTA) intracranial vessel wall sequence (adapted from Qiao et al.²; acquired resolution 0.6x0.6x1.0mm; FOV 200x167x45mm), and at 7T MRI (Philips Healthcare) with a 3D whole-brain T1-weighted magnetic preparation inversion recovery turbo spin-echo (MPIR-TSE) intracranial vessel wall sequence (acquired resolution 0.8x0.8x0.8mm; FOV 250x250x190)³, both before and after contrast administration. Two observers independently scored image quality with three qualitative grading scales for overall artefacts, overall arterial vessel wall visibility, and visibility of all separate vessel walls³; further, presence and contrast enhancement of vessel wall lesions were scored on all intracranial vessel wall images for the arteries of the circle of Willis and its primary branches. In case of disagreement, consensus reading was performed with a third observer. Differences between image quality ratings were tested using a Wilcoxon signed-rank test.7T images showed significantly more artefacts compared to 3T (p<0.001). However, overall visibility of the arterial vessel wall was scored higher at 7T MRI (p=0.003)); this was mainly due to better visibility of vessel walls of the anterior circulation as well as of the posterior cerebral artery (p<0.05; Table 1). Vessel walls of the vertebral and basilar arterial segments showed comparable visibility between both field strengths (p>0.05; Table 1). Inter-rater reproducibility of the scored vessel wall lesions was moderate to good at 3T (Intraclass correlation coefficient (ICC): 0.69; Dice’s similarity coefficient (DSC): 0.68) and 7T (ICC: 0.94; DSC: 0.67). There was substantial to almost perfect agreement between the two raters for assessment of contrast enhancement (kappa 0.845 for 3T and 0.665 for 7T). In total 48 vessel wall lesions were seen on 3T (Table 2; mean: 3 per subject, range: 1-7), of which 7 (15%) showed enhancement. On 7T 79 lesions were seen (Table 2; mean: 5 per subject, range: 1-10), of which 29 (45%) showed enhancement. Twenty-four lesions seen on 3T were also seen on 7T (Table 2; 50% and 30% of the vessel wall lesions identified on 3T and 7T, respectively), several examples are shown in Figure 1 and 2. Most corresponding lesions were present in the vertebral arteries, basilar artery, and internal carotid arteries.This is the first study comparing a dedicated 3T and 7T sequence in their ability to visualize the intracranial vessel wall. Vessel wall visibility was significantly better at 7T even though there were more artefacts hampering assessment. Better visibility at 7T was mainly due to the anterior cerebral circulation and distal posterior circulation (PCA); visibility of the basilar artery and vertebral arteries was comparable on both field strengths. This could be explained by better CSF suppression at 3T in this region compared to the other brain regions, probably because of higher velocity pulsation of the CSF. Overall, more lesions were scored on 7T images; however – surprisingly – only half of all 3T lesions were seen at 7T. Vessel wall lesions were found in all elderly asymptomatic subjects. The total number of identified vessel wall lesions was high, especially for the posterior circulation and specifically the intracranial vertebral artery segments. Since there is not a gold standard for in vivo intracranial vessel wall imaging yet, it is difficult to determine which field strength shows vessel wall lesions best. However, based on the results of this study, we think both 3T and 7T MRI can be used for imaging of the proximal intracranial arteries, which are more richly surrounded by CSF (especially in the elderly population). For the smaller and more distally located arteries 7T may be better in showing the intracranial vessel wall.