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

Abstract

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.

Variability and Standardization of Quantitative Imaging

“… 111 , 112 Similar to the discrepancy among T1 measurement methods, T2 measurement methods are known to show disagreement with each other. 113 Jutras et al 114 reported that the WM T2 of 70 and 50 milliseconds was measured by MET2 and DESPOT2, respectively, in the same subject, partly due to the different weighting of each tissue component by these methods.…”

Reliability and Value of 3D Sequential QUantitative T1‐T2‐T2* MAppings (SQUMA) MR Multi‐Parametric Imaging in Characterizing Carotid Artery Atherosclerosis

“…Furthermore, the scan time of the SQUMA imaging (scan time: 12 minutes) was shorter than that of 2D multi‐contrast vessel wall imaging (total scan time: 20 minutes) 34 and other combinations of quantitative T 1 , T 2 , and T 2 * mapping imaging (where the scan time depends on the acquisition approach). For example, the GOAL‐SNAP 18 technique for T 1 map estimation requires 5 minutes to acquire 0.8 mm isotropic resolution with a field of view of 100 × 100 × 100 mm 3 ; the iMSDE prepared T 2 map acquisition 19 requires 7 minutes 54 seconds to acquire 0.6 × 0.6 × 1.4 mm 3 resolution with a field of view of 140 × 140 × 42 mm 3 . SQUMA imaging ensures the quality and robustness of images without increasing the scan time.…”

“…18 The double inversion recovery (DIR) prepared 2D spin echo sequence and the improved motion-sensitized drivenequilibrium (iMSDE) prepared 3D spin echo or spoiled gradient echo (SPGR) sequence have been utilized for the acquisition of carotid T 2 maps. 19 The Dixon sequence and the MSDE prepared SPGR sequence have been used to acquire carotid T 2 * maps. 20 Investigators have also developed carotid MR quantitative imaging techniques which enable simultaneous acquisition of two MR quantitative parameters with a single sequence.…”

“…Qi et al developed a 3D GOAL‐SNAP sequence with large coverage and isotropic spatial resolution for acquiring carotid T 1 maps 18 . The double inversion recovery (DIR) prepared 2D spin echo sequence and the improved motion‐sensitized driven‐equilibrium (iMSDE) prepared 3D spin echo or spoiled gradient echo (SPGR) sequence have been utilized for the acquisition of carotid T 2 maps 19 . The Dixon sequence and the MSDE prepared SPGR sequence have been used to acquire carotid T 2 * maps 20 .…”

Ferumoxytol-enhanced three-dimensional magnetic resonance imaging of carotid atheroma- a feasibility and temporal dependence study

“…Finally, quantitative T2 (qT2) was performed with a multi-echo variable refocussing flip angle FSE sequence with improved Motion-Sensitized Driven-Equilibrium. The accuracy and repeatability of improved Motion-Sensitized Driven-Equilibrium prepared 3D variable refocussing flip angle fast spin echo for T2 mapping has previously been reported 16 . We used three echo times to generate qT2 maps after practical consideration of scanning time and accuracy.…”