<scp>Fast‐spin‐echo</scp> versus rapid <scp>gradient‐echo</scp> for <scp>3D magnetization‐prepared</scp> acquisitions: Application to inhomogeneous magnetization transfer

International audience; To evaluate the benefits of Fast Spin Echo (FSE) imaging over Rapid Gradient-Echo (RAGE) for Magnetization-prepared inhomogeneous Magnetization Transfer (ihMT) imaging. Methods: A 3D FSE sequence was modified to include an ihMT preparation (ihMT-FSE) with an optional CSF suppression based on an Inversion-Recovery (ihMT-FLAIR). After numerical simulations assessing SNR benefits of FSE and the potential impact of an additional inversion-recovery, ihMT-RAGE, ihMT-FSE and ihMT-FLAIR sequences were compared in a group of 6 healthy volunteers, evaluating image quality, thermal and physiological noise as well as quantification using an ihMTsat approach. A preliminary exploration in the cervical spinal cord was also conducted in a group of 3 healthy volunteers. Results: Several fold improvement in thermal SNR was observed with ihMT-FSE in agreement with numerical simulations. However, we observed significantly higher physiological noise in ihMT-FSE compared to ihMT-RAGE that was mitigated in ihMT-FLAIR, which provided the best total SNR (+74% and 49% compared to ihMT-RAGE in the white and gray matter, p0.004). IhMTsat quantification was successful in all cases with strong correlation between all sequences (r 2 &gt;0.75). Early experiments showed potential for spinal cord imaging. Conclusions: FSE generally offers higher SNR compared to gradient-echo based acquisitions for magnetization-prepared contrasts as illustrated here in the case of ihMT. However, physiological noise has a significant effect, but an IR-based CSF suppression was shown to be efficient in mitigating effects of CSF motion.