Regularly Incremented Phase Encoding – Magnetic Resonance Fingerprinting (RIPE-MRF) for Enhanced Motion Artifact Suppression in Preclinical Cartesian MR Fingerprinting

Abstract

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 T ₁ and 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).

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 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%).

Conclusion

These 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.