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

PurposeThe 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. MethodsAs 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 (T-1) and transverse relaxation time (T-2) measurements, as well as in vivo liver assessments of artifact-to-noise ratio (ANR) and MRF-based T-1 and T-2 mean and standard deviation, were compared between the two methods (n=5). ResultsRIPE-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 T-1 and T-2 measurements in comparison to the SC-MRF method (P< 0.05). The RIPE-MRF and SC-MRF methods displayed similar mean T-1 and T-2 estimates (difference in mean values<10%). ConclusionThese results show that the RIPE-MRF method can provide effective motion artifact suppression with minimal impact on T-1 and T-2 accuracy for in vivo small animal MRI studies. Magn Reson Med 79:2176-2182, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.