Whole Brain Adiabatic T_1rho and Relaxation Along a Fictitious Field Imaging in Healthy Volunteers and Patients With Multiple Sclerosis: Initial Findings

Abstract

Background In preclinical models of multiple sclerosis (MS), both adiabatic T1rho (T1ρadiab) and relaxation along a fictitious field (RAFF) imaging have demonstrated potential to noninvasively characterize MS. Purpose To evaluate the feasibility of whole brain T1ρadiab and RAFF imaging in healthy volunteers and patients with MS. Study Type Single institutional clinical trial. Subjects 38 healthy volunteers (24–69 years) and 21 patients (26–59 years) with MS. Five healthy volunteers underwent a second MR examination performed within 8 days. Clinical disease severity (The Expanded Disability Status Scale [EDSS] and The Multiple Sclerosis Severity Score [MSSS]) was evaluated at baseline and 1‐year follow‐up (FU). Field Strength/Sequence RAFF in second rotating frame of reference (RAFF2) was performed at 3 T using 3D‐fast‐field echo with magnetization preparation, RF amplitude of 11.74 μT while the corresponding value for T1ρadiab was 13.50 μT. T1‐, T2‐, and FLAIR‐weighted images were acquired with reconstruction voxel size 1.0 × 1.0 × 1.0 mm3. Assessment The parametric maps of T1ρadiab and RAFF2 (TRAFF2) were calculated using a monoexponential model. Semi‐automatic segmentation of MS lesions, white matter (WM), and gray matter (GM), and WM tracks was performed using T1‐, T2‐, and FLAIR‐weighted images. Statistical Tests Regression analysis was used to evaluate correlation of T1ρadiab and TRAFF2 with age and disease severity while a Friedman test followed by Wilcoxon Signed Rank test for differences between tissue types. Short‐term repeatability was evaluated on voxel level. Results Both T1ρadiab and TRAFF2 demonstrated good short‐term repeatability with relative differences on voxel level in the range of 6.1%–11.9%. Differences in T1ρadiab and TRAFF2 between the tissue types in MS patients were significant (P < 0.05). T1ρadiab and TRAFF2 correlated (P < 0.001) with baseline EDSS/MSSM and disease progression at FU (P < 0.001). Data Conclusion Whole brain T1ρadiab and TRAFF2 at 3 T was feasible with significant differences in T1ρadiab and TRAFF2 values between tissues types and correlation with disease severity. Evidence Level 1 Technical Efficacy Stage 1