Simultaneous B1 and T1 mapping using spiral multislice variable flip angle acquisitions for whole-brain coverage in less than one minute

Purpose: Variable flip angle (VFA)-based T-1 quantification techniques are highly sensitive to B-1 inhomogeneities and to residual T-2 dependency arising from incomplete spoiling. Here, a rapid spiral VFA acquisition scheme with high spoiling efficiency is proposed for simultaneous whole-brain B-1 and T-1 mapping. Methods: VFA acquisitions at 2 different flip angles are performed to quantify T-1 using a steady-state prepared spiral 2D multislice spoiled gradient-echo sequence with the acquisition of 10 and 20 spiral interleaves at 1.5T and 3T, respectively. Additionally, parallel imaging acceleration of factor 2 is investigated at 3T. The free induction decay induced by the preparation pulse is sampled by a single-shot spiral readout to quantify B-1. Results: The in vitro and in vivo validations yielded good agreement between the derived spiral VFA B-1 and the acquired reference B-1 maps as well as between the B-1-corrected spiral VFA T-1 and the reference T-1 maps. The spiral VFA acquisitions in the human brain delivered artifact-free B-1 and T-1 maps and demonstrated high reproducibility at 1.5T and 3T. Conclusion: Reliable simultaneous spiral VFA B-1 and T-1 quantification was feasible with acquisition times of <1 min for whole-brain coverage at clinically relevant resolution.