Arjen Lindenholz

89 Comparison of 3T Intracranial Vessel Wall MRI Sequences 4 wall. Qualitative assessment of the images in axial plane shows poor visibility of the vessel wall in variant 1 (8 minutes 24 seconds) and 6 (5 minutes 49 seconds), acquired with an isotropic voxel-size. Variant 4 (6 minutes 01 seconds) and 7 (4 minutes 39 seconds), which were acquired with an anisotropic voxel-size, had a higher qualitative assessment score compared with the other variants. Qualitative assessment of the axial, sagittal and coronal images showed that CSF was most suppressed in variant 3 (6 minutes 42 seconds) and 7 (4 minutes 39 seconds). These 2 variants were compared before and after contrast administration in the next paragraph ( Table 2 ). Variant 1 (8 minutes 24 seconds) also had an adequate CSF suppression, but the axial and sagittal images had an overall granular appearance, which made assessment and delineation of the vessel wall with their surrounding CSF challenging. This granular appearance was also seen to a lesser extent in variant 5 (5 minutes 52 seconds) and 6 (5 minutes 49 seconds), but with a worse CSF suppression. In the axial plane the vessel wall was best seen in variant 2 (7 minutes 50 seconds), 3 (6 minutes 42 seconds), 4 (6 minutes 01 seconds) and 7 (4 minutes 49 seconds). In both the sagittal and coronal planes, the vessel wall is of highest quality in the isotropic variant 2 (7 minutes 50 seconds), though the contrast with the surrounding CSF is less, which makes delineation of the outer margins of the vessel wall more difficult. Due to the granular appearance, the perpendicular visibility (sagittal plane) of the middle cerebral artery was poor in variants 1 (8 minutes 24 seconds) and 6 (5 minutes 49 seconds). In the anisotropic variants 3 (6 minutes 42 seconds), 4 (6 minutes 01 seconds) and 7 (4 minutes 39 seconds), the vessel wall could be delineated in the sagittal plane, but the overall appearance was blurrier ( Figure 3 ). All variants had sufficient blood suppression without flow artifacts, which could have limited assessment in the large intracranial arteries. The mean SNRs and CNRs of the clinically most relevant regions, i.e., the basilar and carotid vessel wall and the surrounding CSF, are displayed in Figure 4 , including the statistical comparisons with reference variant 3. The SNR and, more important, the calculated CNR results for all variants are shown in Supplemental Table 1 . Relatively high SNRs of the vessel wall were measured for variant 2 (7 minutes 50 seconds), 4 (6 minutes 01 seconds) and 7 (4 minutes 39 seconds). In these 3 variants, the SNR of the intracranial internal carotid vessel wall was > 21, and the SNR of the basilar vessel wall > 15. All 7 variants showed good blood signal suppression, which resulted in most variants having a relatively high CNR between blood and the intracranial internal carotid vessel wall (CNRs ranging from 5.7 to 23, Supplemental Table 1 ). All except 1 variant perform borderline in the CNRs of the carotid vessel wall with the surrounding CSF (ranging from 1.3 to 3.2). Variant 7 had the highest CNR between the carotid vessel wall and the surrounding CSF (4.8). All variants performed better in the CNRs between the basilar artery vessel wall and CSF which are comparable in 6 of 7 variants (ranging from 3.6 to 5.3); only variant 4 (6 minutes 01 seconds) had a higher CNR (8.4), but also a large standard deviation (3.9, Figure 4 ).