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Simultaneous T1 , T2 , and T1ρ relaxation mapping of the lower leg muscle with MR fingerprinting. Magn Reson Med 2021 Jul;86(1):372-381

Date

02/09/2021

Pubmed ID

33554369

Pubmed Central ID

PMC8005468

DOI

10.1002/mrm.28704

Scopus ID

2-s2.0-85100576976 (requires institutional sign-in at Scopus site)   13 Citations

Abstract

PURPOSE: To develop a novel MR-fingerprinting (MRF) pulse sequence that is insensitive to B1+ and B0 imperfections for simultaneous T1 , T2 , and T1ρ relaxation mapping.

METHODS: We implemented a totally balanced spin-lock (TB-SL) module to encode T1ρ relaxation into an existing MRF framework that encoded T1 and T2 . The spin-lock module used two 180° pulses with compensatory phases to reduce T1ρ sensitivity to B1 and B0 inhomogeneities. We compared T1ρ measured using TB-SL MRF in Bloch simulations, model agar phantoms, and in vivo experiments to those with a self-compensated spin-lock preparation module (SC-SL). The TB-SL MRF repeatability was evaluated in maps acquired in the lower leg skeletal muscle of 12 diabetic peripheral neuropathy patients, scanned two times each during visits separated by about 30 days.

RESULTS: The phantom relaxation times measured with TB-SL and SC-SL MRF were in good agreement with reference values in regions with low B1 inhomogeneities. Compared with SC-SL, TB-SL MRF showed in experiments greater robustness against severe B1 inhomogeneities and in Bloch simulations greater robustness against B1 and B0 . We measured with TB-SL MRF an average T1 = 950.1 ± 28.7 ms, T2 = 26.0 ± 1.2 ms, and T1ρ = 31.7 ± 3.2 ms in skeletal muscle across patients. Bland-Altman analysis demonstrated low bias between TB-SL and SC-SL MRF and between TB-SL MRF maps acquired in two visits. The coefficient of variation was less than 3% for all measurements.

CONCLUSION: The proposed TB-SL MRF sequence is fast and insensitive to B1+ and B0 imperfections. It can simultaneously map T1 , T2 , T1ρ , and B1+ in a single scan and can potentially be used to study muscle composition.

Author List

Sharafi A, Medina K, Zibetti MWV, Rao S, Cloos MA, Brown R, Regatte RR

Author

Azadeh Sharafi PhD Assistant Professor in the Radiology department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Humans
Image Processing, Computer-Assisted
Leg
Magnetic Resonance Imaging
Muscle, Skeletal
Phantoms, Imaging