Robust variable flip angle T1-mapping by time optimal control

Motivation: Accurate T1-mapping is essential in MRI for insights into brain microstructure. While a variety of methods are available, inversion recovery is the gold standard, but requires lengthy acquisition times. Variable flip angle (VFA) T1-mapping offers a faster alternative, but is highly sensitive to B1+-field imperfections. Goal(s): To enhance the accuracy of VFA T1-mapping with robust excitation pulses by time-optimal control. Approach: Excitation pulses were designed using optimal control, followed by VFA-mapping in phantom. Results were compared against VFA T1-values obtained with block pulses and inversion recovery as the ground truth. Results: VFA T1-mapping with optimal control pulses demonstrates improved accuracy over block pulses. Impact: The advancement in VFA T1-mapping using robust excitation pulses designed by time-optimal control reduces scan time as no additional acquisition of B1+-maps is necessary, and it minimizes potential errors associated with inaccuracies in the B1+-maps and their correction.