Improved T1 and T2 mapping in 3D-QALAS using temporal subspaces and Cramer-Rao-bound flip angle optimization enabled by auto-differentiation

3D-QALAS utilizes an interleaved Look-Locker acquisition with T2-preparation pulses for full brain quantification of T1 and T2. The sequence applies constant flip-angles and suffers from blurring due to k-space modulation from signal evolution during the lengthy echo-train. This abstract improves 3D-QALAS by (1) resolving the full temporal signal with subspace reconstructions to eliminate blurring, (2) optimizing acquisition flip angles with the Cramer-Rao-Bound using simulations compatible with auto-differentiation, and (3) decreasing the number of acquisitions within a repetition time, which could enable up to 40% reduced scan time. Simulation, phantom, and in-vivo results demonstrate the efficacy of the proposed sequence improvements.