Water T 2 Mapping in Fatty Infiltrated Thigh Muscles of Patients With Neuromuscular Diseases Using a T 2 ‐Prepared 3D Turbo Spin Echo With SPAIR

Background Muscle water T 2 (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 T 2 ‐prepared 3D turbo spin echo (TSE) is an alternative method for T 2 mapping, but has been only applied in healthy muscles. Purpose To examine the performance of T 2 ‐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 T 2 ‐prepared stimulated echo acquisition mode (STEAM) magnetic resonance spectroscopy (MRS), SPAIR STEAM MRS, and SPAIR T 2 ‐prepared STEAM MRS were performed in the subcutaneous fat of a healthy volunteer's thigh. T 2 mapping based on SPAIR 2D MESE and SPAIR T 2 ‐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 T 2 ‐prepared 3D TSE was simulated using Bloch simulations. The in vivo T 2 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 T 2 for the SPAIR T 2 ‐prepared 3D TSE sequence remained constant within a relative error of not more than 4% up to a fat fraction of 80%. In vivo T 2 values of SPAIR T 2 ‐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 T 2 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 T 2 ‐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.