Feasibility and reproducibility of whole brain myelin water mapping in 4 minutes using fast acquisition with spiral trajectory and adiabatic T2prep (FAST-T2) at 3T

Abstract

Purpose To develop and measure the reproducibility of 4-min whole brain myelin water fraction (MWF) mapping using fast acquisition with spiral trajectory and T2prep (FAST-T2) sequence at 3T. Methods Experiments were performed on phantoms, 13 volunteers, and 16 patients with multiple sclerosis. MWF maps were extracted using a spatially constrained non-linear algorithm. The proposed adiabatic modified BIR-4 (mBIR-4) T2prep was compared with the conventional composite T2prep (COMP). The effect of reducing the number of echo times (TEs) from 15 to 6 (reducing scan time from 10 to 4 min) was evaluated. Reproducibility was assessed using correlation analysis, coefficient of variation (COV), and Bland–Altman plots. Results Compared with COMP, mBIR-4 provided more accurate T2 in phantoms and better MWF maps in human brains. Reducing the number of TEs had a negligible effect on MWF map quality, with a regional MWF difference of <0.8%. Regional MWFs obtained by repeated scans showed excellent correlation (R = 0.99), low COV (1.3%–2.4%), and negligible bias within ±1% limits of agreement. On a voxel-wise basis, the agreement remained strong (correlation R = 0.89 ± 0.03, bias = 0.01% ± 0.29%, limits of agreement = [−3.35% ± 0.73%, 3.33% ± 0.61%]). Conclusion Whole brain MWF mapping with adiabatic FAST-T2 is feasible in 4 min and provides good intrasite reproducibility.

Combining Quantitative Susceptibility Mapping with Automatic Zero Reference (QSM0) and Myelin Water Fraction Imaging to Quantify Iron-Related Myelin Damage in Chronic Active MS Lesions

“…MWF maps were reconstructed from FAST-T2 data using a multi-voxel nonlinear least-squares data-fitting algorithm with spatial smoothness constraints. 25 The lower and upper T2 bounds for each of the three water pools (in milliseconds) were set to [5 20], [20 200], and [200 2000], respectively (corresponding to myelin water, intra/extra-cellular water, and long-T2 water such as CSF). MWF was calculated as the ratio of the myelin water signal and the total water signal within a voxel.…”

“…This study aimed to address these challenges by combining two recently developed techniques, myelin water fraction (MWF) imaging using fast acquisition with spiral trajectory and T2prep (FAST-T2) 24, 25 and QSM with automatic uniform CSF zero reference (QSM0). MWF is a well-validated quantitative MRI biomarker for myelin, 26, 27 which can be mapped efficiently and reproducibly with FAST-T2.…”

“…MWF is a well-validated quantitative MRI biomarker for myelin, 26, 27 which can be mapped efficiently and reproducibly with FAST-T2. 25, 28 The QSM0 algorithm improves QSM zero reference selection by enforcing susceptibility homogeneity of CSF within the brain ventricles and eliminating the need for manual drawing of CSF region-of-interest (ROI). QSM0 and MWF were used to identify MS lesions with a hyperintense rim pattern consistent with iron deposition and to assess the extent of myelin damage found within these lesions.…”

A new analysis approach for T2 relaxometry myelin water quantification: Orthogonal Matching Pursuit

“…Recently, several studies have already focused on fast acquisition of multiecho data for the purpose of MWF mapping. For instance, Prasloski et al showed that whole brain MWF mapping was possible under 15 min using a gradient‐spin echo sequence with 32 TEs, whereas Nguyen et al showed that even faster whole brain MWF mapping was possible acquiring 6 TEs in 4 min using a modified T 2 prep sequence . In this study, we already showed the applicability of the OMP algorithm for multiecho data acquired using a 3D GRASE sequences.…”

Rapid simultaneous high-resolution mapping of myelin water fraction and relaxation times in human brain using BMC-mcDESPOT

“…demonstrated in-vivo MCR in the human brain for myelin mapping using MRI (21). Since then, MCR has become an active area of research, with several methods having been developed to either accelerate data acquisition (23, 28, 29, 32, 36, 37, 39, 40, 55) or to improve parameter determination (23, 25, 36, 44, 56–65). Among these, mcDESPOT permits rapid whole-brain coverage, and so may have particular potential for clinical investigations, especially those involving patients with limited ability to remain stationary for the lengthy duration of MRI studies.…”