Optimized inversion-time schedules for quantitative T measurements based on high-resolution multi-inversion EPI.

PURPOSE

Demonstrate an optimized multi-inversion echo-planar imaging technique to accelerate quantitative T mapping by judicious selection of inversion times for each slice.

METHODS

Slice ordering is optimized to maximize discrimination between tissues with different T values. The optimized slice orderings are tested in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom and compared with an unoptimized 21-measurement acquisition. The utility of the method is demonstrated in a healthy subject in vivo at 3 T and validated with a gold-standard inversion-recovery sequence. The in vivo precision of our technique was tested by repeated scans of the same subject within a scan session and across scan sessions, occurring 28 days apart.

RESULTS

Phantom measurements yielded good agreement (R  = 0.99) between the T estimates from the proposed optimized protocol, reference values from the National Institute of Standards and Technology phantom and gold-standard inversion-recovery values, as well as a negligible estimation bias that was slightly lower than that from the unoptimized 21-measurement protocol (0.74 versus 19 ms). The range of values for the scan-rescan coefficient of variation was 0.86 to 0.93 (within session) and 0.83 to 0.92 (across sessions) across all scan durations tested.

CONCLUSIONS

Optimized slice orderings allow faster quantitative T mapping. The optimized sequence yielded accurate and precise T maps. Magn Reson Med 79:2101-2112, 2018. © 2017 International Society for Magnetic Resonance in Medicine.