High-Resolution 3D Turbo Spin-Echo Wrist MRI at 7T Accelerated by Compressed Sensing

This study aimed to obtain high-resolution 3D isotropic turbo spin-echo (TSE) wrist MRI acquisitions at 7T, with and without fat suppression, facilitated by compressed-sensing (CS) acceleration. In 16 healthy subjects, fat-suppressed (FS) and nonfat-suppressed (NFS) TSE wrist images were obtained. The protocol consisted of a SENSE-accelerated scan, with an isotropic voxel size of 0.45 mm and acquisition time of 7 min ("SENSE45"), a 0.45-mm, 4-min CS-accelerated scan ("CS45"), and a 0.35-mm, 7-min CS-accelerated scan ("CS35"). For two subjects, additional 0.45-mm, 4-min SENSE-accelerated scans were acquired ("High-SENSE"). For the NFS scans, refocusing pulses were optimized to mitigate water-fat chemical-shift artifacts in the slab-selection direction. Anatomical visibility of wrist structures and image quality were assessed qualitatively and through musculoskeletal radiologist grading. The use of nonselective hard refocusing pulses with optimized bandwidths and a center frequency in between water and fat enabled NFS imaging. The image quality of the faster CS45 scans was lower than for SENSE45, with statistically significantly different grading in 9/16 (FS) and 2/6 (NFS) grading parameters. Nonetheless, a similar scan time reduction could not be achieved using High-SENSE. No distinct benefit of CS35 compared to SENSE45 was evident in either the FS or NFS scans. NFS CS35 exhibited enhanced bone sharpness compared to SENSE45 for some subjects, yet on a group level, the difference was not statistically significant. In conclusion, for maintained voxel size, CS presents the opportunity to achieve shorter scan times than possible with SENSE alone, but with reduced image quality. For maintained scan time, although higher resolution CS incidentally showed a promising increase in NFS bone sharpness compared to SENSE, it does not present an unequivocal advantage for 3D 7-T TSE wrist MRI at this stage. Further optimization of the acquisition and reconstruction process is recommended.