A Comparison of Black-blood T2 Mapping Sequences for Carotid Vessel Wall Imaging at 3T: An Assessment of Accuracy and Repeatability

Purpose: This study is to compare the accuracy of four different black-blood T-2 mapping sequences in carotid vessel wall. Methods: Four different black-blood T-2 mapping sequences were developed and tested through phantom experiments and 17 healthy volunteers. The four sequences were: 1) double inversion-recovery (DIR) prepared 2D multi-echo spin-echo (MESE); 2) DIR-prepared 2D multi-echo fast spin-echo (MEFSE); 3) improved motion-sensitized driven-equilibrium (iMSDE) prepared 3D FSE and 4) iMSDE prepared 3D fast spoiled gradient echo (FSPGR). The concordance correlation coefficient and Bland-Altman statistics were used to compare the sequences with a gold-standard 2D MESE, without blood suppression in phantom studies. The volunteers were scanned twice to test the repeatability. Mean and standard deviation of vessel wall T-2, signal-to-noise (SNR), the coefficient of variance and interclass coefficient (ICC) of the two scans were compared. Results: The phantom study demonstrated that T-2 measurements had high concordance with respect to the gold-standard (all r values >0.9). In the volunteer study, the DIR 2D MEFSE had significantly higher T-2 values than the other three sequences (P < 0.01). There was no difference in T-2 measurements obtained using the other three sequences (P > 0.05). iMSDE 3D FSE had the highest SNR (P < 0.05) compared with the other three sequences. The 2D DIR MESE has the highest repeatability (ICC: 0.96, [95% CI: 0.88-0.99]). Conclusion: Although accurate T-2 measurements can be achieved in phantom by the four sequences, in vivo vessel wall T-2 quantification shows significant differences. The in vivo images can be influenced by multiple factors including black-blood preparation and acquisition method. Therefore, a careful choice of acquisition methods and analysis of the confounding factors are required for accurate in vivo carotid vessel wall T-2 measurements. From the settings in this study, the iMSDE prepared 3D FSE is preferred for the future volunteer/patient scans.