Isotropic resolution diffusion tensor imaging of lumbosacral and sciatic nerves using a phase‐corrected diffusion‐prepared 3D turbo spin echo

Abstract

PurposeTo perform in vivo isotropic‐resolution diffusion tensor imaging (DTI) of lumbosacral and sciatic nerves with a phase‐navigated diffusion‐prepared (DP) 3D turbo spin echo (TSE) acquisition and modified reconstruction incorporating intershot phase‐error correction and to investigate the improvement on image quality and diffusion quantification with the proposed phase correction.MethodsPhase‐navigated DP 3D TSE included magnitude stabilizers to minimize motion and eddy‐current effects on the signal magnitude. Phase navigation of motion‐induced phase errors was introduced before readout in 3D TSE. DTI of lower back nerves was performed in vivo using 3D TSE and single‐shot echo planar imaging (ss‐EPI) in 13 subjects. Diffusion data were phase‐corrected per k z plane with respect to T2‐weighted data. The effects of motion‐induced phase errors on DTI quantification was assessed for 3D TSE and compared with ss‐EPI.ResultsNon–phase‐corrected 3D TSE resulted in artifacts in diffusion‐weighted images and overestimated DTI parameters in the sciatic nerve (mean diffusivity [MD] = 2.06 ± 0.45). Phase correction of 3D TSE DTI data resulted in reductions in all DTI parameters (MD = 1.73 ± 0.26) of statistical significance (P ≤ 0.001) and in closer agreement with ss‐EPI DTI parameters (MD = 1.62 ± 0.21).ConclusionDP 3D TSE with phase correction allows distortion‐free isotropic diffusion imaging of lower back nerves with robustness to motion‐induced artifacts and DTI quantification errors. Magn Reson Med 80:609–618, 2018. © 2018 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Denoising of diffusion MRI improves peripheral nerve conspicuity and reproducibility

“…Diffusion MRI (dMRI) is a noninvasive MR technique that can provide objective, quantitative measurements that reflect microstructural nerve integrity . dMRI is based on the naturally occurring Brownian motion of water molecules.…”

“…1 Diffusion MRI (dMRI) is a noninvasive MR technique that can provide objective, quantitative measurements that reflect microstructural nerve integrity. [4][5][6][7] dMRI is based on the naturally occurring Brownian motion of water molecules. The highly organized microstructure of a nerve's axon bundles directionally restricts diffusion (anisotropy), in comparison to an unconstrained space where water molecules freely diffuse in all directions (isotropy).…”

Multishot diffusion‐prepared magnitude‐stabilized balanced steady‐state free precession sequence for distortion‐free diffusion imaging

“…The MS approach was inspired by the phase‐insensitive preparation method proposed by Alsop, which uses a 90˚ pulse after the diffusion module and several dephasing and rephasing gradients throughout the sequence to eliminate the non‐CPMG (Carr–Purcell–Meiboom–Gill) component in single‐shot diffusion‐weighted TSE imaging . Similar strategies have been applied to achieve diffusion imaging with fast low‐angle shot (FLASH) and TSE readouts . However, in all multishot studies, only Zhang et al and Cervantes et al implemented phase correction to deal with the ghosting artifacts originated from multishot phase inconsistency, whereas the others did not have further correction methods, leaving the image vulnerable to shot‐to‐shot phase inconsistency.…”

“…In this work, although the MS strategy was similar as previous works, the motivation and purpose of adding those stabilizer gradients are different. In previous studies, the stabilizer gradients were added to only refocus the stimulated echo and avoid T1‐dependent loss of diffusion information in the FLASH readout or to eliminate the non‐CPMG component in the TSE readout . However, in our work, the stabilizer approach was developed to transform signal magnitude inconsistencies into phase inconsistencies in DP diffusion MRI.…”

Three‐dimensional diffusion imaging with spiral encoded navigators from stimulated echoes (3D‐DISPENSE)

“…22 Under the same assumption, Cervantes et al achieved isotropic-resolution 3D DTI of lower extremity nerves using a 2D navigator. 23 McNab et al and O'Halloran et al batched 2D navigators with the same cardiac phase together to form a satisfactory 3D navigator assuming cardiac motion was the dominant source for the phase incoherence. In this way, they achieved high-resolution 3D DWI of the brain.…”