Mitigating MR fingerprinting undersampling errors is more effective through sequence optimization than via low rank reconstruction

Motivation: To reduce undersampling errors in MR Fingerprinting maps, both sequence optimization and low rank (LR) reconstruction methods have been proposed , but these have not been compared or combined. Goal(s): To compare the effectiveness of LR-reconstruction and sequence optimization for reducing undersampling errors. Approach: Undersampled 2D spiral MRF data as acquired with 7 different flip angle patterns in 6 healthy subjects are reconstructed with the standard vendor reconstruction and an in-house LR-reconstruction and compared to fully-sampled MRF T1- and T2-maps. Results: Undersampling-optimized sequences showed a reduced error compared to other sequences, even after LR-reconstruction. Impact: We show that optimized flip-angle patterns with or without LR-reconstruction outperform traditional schemes with LR reconstruction. Inclusion of LR-reconstruction in the optimization step is not essential, when designing sequences that minimize undersampling artifacts.