Spiral Blurring Correction with Water-Fat Separation for Magnetic Resonance Fingerprinting in the Breast.

Purpose: Magnetic resonance fingerprinting (MRF) with spiral readout enables rapid quantification of tissue relaxation times. However, it is prone to blurring because of off-resonance effects. Hence, fat blurring into adjacent regions might prevent identification of small tumors by their quantitative T-1 and T-2 values. This study aims to correct for the blurring artifacts, thereby enabling fast quantitative mapping in the female breast. Methods: The impact of fat blurring on spiral MRF results was first assessed by simulations. Then, MRF was combined with 3-point Dixon water-fat separation and spiral blurring correction based on conjugate phase reconstruction. The approach was assessed in phantom experiments and compared to Cartesian reference measurements, namely inversion recovery (IR), multi-echo spin echo (MESE), and Cartesian MRF, by normalized root-mean-square error (NRMSE) and SD calculations. Feasibility is further demonstrated in vivo for quantitative breast measurements of 6 healthy female volunteers, age range 24-31 y. Results: In the phantom experiment, the blurring correction reduced the NRMSE per phantom vial on average from 16% to 8% for T-1 and from 18% to 11% for T-2 when comparing spiral MRF to IR/MESE sequences. When comparing to Cartesian MRF, the NRMSE reduced from 15% to 8% for T-1 and from 12% to 7% for T-2. Furthermore, SDs decreased. In vivo, the blurring correction removed fat bias on T-1/T-2 from a rim of similar to 7-8 mm width adjacent to fatty structures. Conclusion: The blurring correction for spiral MRF yields improved quantitative maps in the presence of water and fat.