Regularly incremented phase encoding – MR fingerprinting (RIPE-MRF) for enhanced motion artifact suppression in preclinical cartesian MR fingerprinting

Purpose The regularly incremented phase encoding–magnetic resonance fingerprinting (RIPE-MRF) method is introduced to limit the sensitivity of preclinical MRF assessments to pulsatile and respiratory motion artifacts. Methods As compared to previously reported standard Cartesian–MRF methods (SC-MRF), the proposed RIPE-MRF method uses a modified Cartesian trajectory that varies the acquired phase-encoding line within each dynamic MRF dataset. Phantoms and mice were scanned without gating or triggering on a 7T preclinical MRI scanner using the RIPE-MRF and SC-MRF methods. In vitro phantom longitudinal relaxation time (T1) and transverse relaxation time (T2) measurements, as well as in vivo liver assessments of artifact-to-noise ratio (ANR) and MRF-based T1 and T2 mean and standard deviation, were compared between the two methods (n = 5). Results RIPE-MRF showed significant ANR reductions in regions of pulsatility (P < 0.005) and respiratory motion (P < 0.0005). RIPE-MRF also exhibited improved precision in T1 and T2 measurements in comparison to the SC-MRF method (P <  0.05). The RIPE-MRF and SC-MRF methods displayed similar mean T1 and T2 estimates (difference in mean values < 10%). Conclusion These results show that the RIPE-MRF method can provide effective motion artifact suppression with minimal impact on T1 and T2 accuracy for in vivo small animal MRI studies. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine.