Citation

Wright D, Johnston L, Kershaw J, Ordidge R, O'Brien TJ, Shultz SR. J. Neurotrauma 2017; 34(13): 2109-2118.

Affiliation

University of Melbourne, Medicine , Melbourne Brain Centre , Royal Parade , Level 1, Room 1.02 , Parkville, Victoria, Australia , 3050 ; sshultz@unimelb.edu.au.

Copyright

(Copyright © 2017, Mary Ann Liebert Publishers)

DOI

10.1089/neu.2016.4730

PMID

28152648

Abstract

Traumatic brain injury (TBI) has been assessed with diffusion tensor imaging (DTI), a commonly used magnetic resonance imaging (MRI) marker for white matter integrity. However, as the DTI model only fits a single fibre orientation, results can become confounded in regions of 'crossing' white matter fibres. In contrast, constrained spherical deconvolution estimates a fibre orientation distribution directly from high angular resolution diffusion weighted images. Consequently, constrained spherical deconvolution-based measures such as apparent fibre density and track-weighted imaging metrics (including tract density imaging, average pathlength mapping, and mean curvature), may be more sensitive than DTI metrics to white matter injury following TBI. As such, this study administered the lateral fluid percussion injury (FPI) model of TBI, assessed for changes in apparent fibre density, and track-weighted imaging metrics, and compared these results to the DTI metrics fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD). Rats received either an FPI (n = 11) or sham injury (n = 9) and after a recovery period of 12 weeks underwent MRI. Apparent fibre density was calculated as described previously and statistical testing was performed using connectivity-based fixel enhancement. Track-weighted imaging and DTI metrics were assessed using voxel-wise non-parametric permutation testing. We found that rats given an FPI had significantly reduced apparent fibre density, tract density, average pathlength and mean curvature when compared to sham-injured rats and significant changes in DTI metrics including reduced FA and increased MD, RD and AD. However, the latter DTI metrics identified fewer voxels affected by TBI. Additionally, analysis of apparent fibre density with connectivity-based fixel enhancement was the only method that identified damage within the corticospinal tract of rats given an FPI. These results support the use of constrained spherical deconvolution, in conjunction with DTI metrics, to better assess disease progression and treatment following TBI.

Language: en

Keywords

AXONAL INJURY; BIOMARKERS; Diffusion Tensor Imaging; MRI