Feasibility of MR fingerprinting using a high-performance 0.55 T MRI system

Abstract

Background: MR fingerprinting (MRF) is a versatile method for rapid multi-parametric quantification. The application of MRF for lower MRI field could enable multi-contrast imaging and improve exam efficiency on these systems. The purpose of this work is to demonstrate the feasibility of 3D whole-brain T1 and T2 mapping using MR fingerprinting on a contemporary 0.55 T MRI system.

Materials and methods: A 3D whole brain stack-of-spirals FISP MRF sequence was implemented for 0.55 T. Quantification was validated using the NIST/ISMRM Quantitative MRI phantom, and T1 and T2 values of white matter, gray matter, and cerebrospinal fluid were measured in 19 healthy subjects. To assess MRF performance in the lower SNR regime of 0.55 T, measurement precision was calculated from 100 simulated pseudo-replicas of in vivo data and within-session measurement repeatability was evaluated.

Results: T1 and T2 values calculated by MRF were strongly correlated to standard measurements in the ISMRM/NIST MRI system phantom (R2 > 0.99), with a small constant bias of approximately 5 ms in T2 values. 3D stack-of-spirals MRF was successfully applied for whole brain quantitative T1 and T2 at 0.55 T, with spatial resolution of 1.2 mm × 1.2 mm × 5 mm, and acquisition time of 8.5 min. Moreover, the T1 and T2 quantifications had precision <5%, despite the lower SNR of 0.55 T.

Conclusion: A 3D whole-brain stack-of-spirals FISP MRF sequence is feasible for T1 and T2 mapping at 0.55 T.

Trial registration: ClinicalTrials.gov NCT03331380.

Keywords: Low field; MR fingerprinting; Quantitative MR; Rapid imaging.

Copyright © 2021. Published by Elsevier Inc.

Figures

Fig. 1.

ISMRM/NIST MRI system phantom measurements. Correlation of MRF T1 values (A) and T2 values (B) to standard T1 and T2 measurements. The black line is the line of identity and error bars represent standard deviations within each vial.

Fig. 2.

Multi-slice (A) proton density maps, (B) T1 maps, and (C) T2 maps from MRF in a single volunteer demonstrating volumetric MRF coverage at 0.55 T.

Fig. 3.

(A) T1 maps and (B) T2 maps from 19 healthy subjects in a single axial slice.

Fig. 4.

Precision maps showing the normalized range of A) T1 and B) T2 values calculated using MRF. The range of fitted T1 and T2 values, normalized to the mean, was generated from 100 pseudo-replicas with white noise in a single healthy volunteer. Pixels with 0% value indicate no deviations in quantitative value across 100 pseudo-replicas.