Water T2 Mapping in Fatty Infiltrated Thigh Muscles of Patients With Neuromuscular Diseases Using a T2 -Prepared 3D Turbo Spin Echo With SPAIR

Abstract

Background: Muscle water T₂ (T_2w ) has been proposed as a biomarker to monitor disease activity and therapy effectiveness in patients with neuromuscular diseases (NMD). Multi-echo spin-echo (MESE) is known to be affected by fatty infiltration. A T₂ -prepared 3D turbo spin echo (TSE) is an alternative method for T₂ mapping, but has been only applied in healthy muscles.

Purpose: To examine the performance of T₂ -prepared 3D TSE in combination with spectral adiabatic inversion recovery (SPAIR) in measuring T_2w in fatty infiltrated muscles based on simulations and in vivo measurements in thigh muscles of patients with NMD.

Study type: Prospective.

Subjects: One healthy volunteer, 34 NMD patients.

Field strength/sequence: T₂ -prepared stimulated echo acquisition mode (STEAM) magnetic resonance spectroscopy (MRS), SPAIR STEAM MRS, and SPAIR T₂ -prepared STEAM MRS were performed in the subcutaneous fat of a healthy volunteer's thigh. T₂ mapping based on SPAIR 2D MESE and SPAIR T₂ -prepared 3D TSE was performed in the NMD patients' thigh region. Multi-TE STEAM MRS was performed for measuring a reference T_2w at different thigh locations.

Assessment: The behavior of the fat spectrum in the SPAIR T₂ -prepared 3D TSE was simulated using Bloch simulations. The in vivo T₂ results of the imaging methods were compared to the in vivo T_2w MRS results.

Statistical tests: Pearson correlation coefficient with slope and intercept, relative error.

Results: The simulated T₂ for the SPAIR T₂ -prepared 3D TSE sequence remained constant within a relative error of not more than 4% up to a fat fraction of 80%. In vivo T₂ values of SPAIR T₂ -prepared 3D TSE were in good agreement with the T_2w values of STEAM MRS (R = 0.86; slope = 1.12; intercept = -1.41 ms). In vivo T₂ values of SPAIR 2D MESE showed large deviations from the T_2w values of STEAM MRS (R = 0.14; slope = 0.32; intercept = 38.83 ms).

Data conclusion: The proposed SPAIR T₂ -prepared 3D TSE shows reduced sensitivity to fatty infiltration for T_2w mapping in the thigh muscles of NMD patients.

Level of evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1727-1736.

Keywords: MRS; SPAIR T2-prepared 3D TSE; T2 mapping; fatty infiltration; neuromuscular diseases (NMD); skeletal muscle water T2.