Respiratory-Resolved Isotropic 3D T1 Mapping of the Carotid Vessel Wall with B1 + Correction (CARISMAT1C).

PURPOSE:To develop, optimize, and characterize a respiratory motion-resolved free-running isotropic 3D carotid vessel wall T1 mapping technique named CARISMAT1C. METHODS:An inversion-recovery gradient-echo free-running pulse sequence with interleaved double flip-angle (2FA) was implemented, and an extended-phase-graph dictionary was used to map the T1 relaxation time. In a phantom, the T1 accuracy was compared to that of a single-flip-angle (1FA) variant, the inversion-recovery spin-echo reference, and clinical routine MOLLI, while the T1 precision of several phyllotaxis-based radial trajectories was compared. The most precise sequence was used in 11 healthy volunteers (25 ± 3Y, 3F). A synthetic 3D gray-blood image was reconstructed from the source images and used to delineate the internal, external, and common carotid arteries. T1 values across artery sections were compared to those of MOLLI. RESULTS:In the phantom, the 2FA variant had higher T1 agreement with the IR-SE reference than 1FA or MOLLI. The top-to-bottom phyllotaxis trajectory with golden-step shuffling was the most precise and was retained for in vivo scans. End-expiratory carotid vessel wall T1 values (1185 ± 42 ms) were similar to those obtained with MOLLI (1162 ± 84 ms, p = 0.37) and showed less intersubject variability and high interscan repeatability. No significant differences were found across arterial segments in the vessel wall T1 values. CONCLUSION:CARISMAT1C had high T1 accuracy in phantoms and high T1 precision in vivo in different sections of the carotid artery tree.