Arjen Lindenholz

92 CHAPTER 4 Comparison of variant 3 (6 minutes 42 seconds) versus variant 7 (4 minutes 39 seconds) The average SNRs and CNRs of both precontrast and postcontrast images of variant 3 and variant 7 are shown in Table 2 . Comparing SNRs and CNRs of the precontrast and postcontrast scans ( Table 2 ) for variant 3 and 7 showed that tissue, the basilar vessel wall, suprasellar CSF of only variant 7, pontine CSF and blood SNR did not differ significantly (all p-values > 0.008; Supplemental Table 2 ), while the SNR of the carotid vessel wall of variant 7 (p = 0.005) and the CNRs between the carotid vessel wall and CSF (p = 0.005 and 0.007 for variant 3 and 7, respectively) tended to be higher for the postcontrast images. Significant differences for the SNR pituitary gland were expected because of a strong enhancing pituitary gland on postcontrast images. For both precontrast and postcontrast vessel wall images, the SNRs and CNRs of variant 7 (4 minutes 39 seconds) were higher than those of variant 3 (6 minutes 42 seconds). These differences were all significant (p < 0.008), except for the SNR suprasellar CSF of variant 7, the CNR basilar wall–CSF of both variants (p = 0.059 and p = 0.285) and the CNR carotid vessel wall-blood of variant 3 (p = 0.013) ( Table 2 ). Table 2. SNRs and CNRs of the precontrast and postcontrast scan variants 3 and variant 7 Precontrast Postcontrast T 1W VIRTA T 1W VIRTA p-value T 1W VIRTA T 1W VIRTA p-value variant 3 E variant 7 variant 3 E variant 7 SNR tissue A 28.0 ± 1.8 40.5 ± 3.4 0.005 27.9 ± 1.3 42.4 ± 2.8 0.005 SNR carotid vessel wall B 15.3 ± 1.4 20.8 ± 2.7 0.005 17.2 ± 0.9 26.4 ± 4.0 0.005 SNR basilary vessel wall 13.0 ± 1.4 15.9 ± 1.7 0.005 13.4 ± 2.4 19.2 ± 1.8 0.005 SNR suprasellar CSF 9.1 ± 2.0 11.9 ± 2.2 0.007 11.3 ± 0.7 14.1 ± 2.4 0.013 SNR pontine CSF 5.9 ± 2.1 8.0 ± 2.0 0.007 6.5 ± 1.8 11.2 ± 2.6 0.007 SNR blood 3.6 ± 0.6 5.4 ± 1.2 0.005 3.8 ± 0.5 6.3 ± 1.4 0.007 SNR pituitary gland 23.0 ± 3.4 33.4 ± 4.7 0.005 33.3 ± 3.5 49.5 ± 6.7 0.005 CNR carotid vessel wall-CSF C 6.1 ± 1.6 9.0 ± 1.5 0.005 6.0 ± 0.7 12.3 ± 3.6 0.007 CNR basilary vessel wall-CSF D 7.2 ± 1.4 7.9 ± 1.4 0.059 7.0 ± 2.0 8.0 ± 1.9 0.285 CNR carotid vessel wall B -blood 11.6 ± 1.3 15.5 ± 2.9 0.013 13.5 ± 1.0 20.1 ± 3.8 0.007 Mean and standard deviations (expressed as mean ± SD) are calculated over 10 subjects. A Wilcoxon signed-rank test was used to compare the differences between (I) precontrast variant 3 and 7 and (II) postcontrast variant 3 and 7 (additional statistical comparisons are shown in Supplemental Table 2 ). A. Tissue region of interest (ROI) is located at the left orbital gyri. B. The mean of the left and right distal intracranial internal carotid artery. C. Suprasellar CSF is used as reference. D. Pontine CSF is used as reference. E. Currently used in our clinic. VIRTA = volumetric isotropically reconstructed turbo spin echo acquisition, SNR = signal-to-noise ratio, CNR = contrast-to-noise ratio, CSF = cerebrospinal fluid, Bold = statistically significant (p < 0.008).