Diffusion MRI and the detection of alterations following traumatic brain injury

Abstract

This article provides a review of brain tissue alterations that may be detectable using diffusion MRI (dMRI) approaches and an overview and perspective on the modern dMRI toolkits for characterizing alterations that follow traumatic brain injury (TBI). Non-invasive imaging is a cornerstone of clinical treatment of TBI and has become increasingly used for pre-clinical and basic research studies. In particular, quantitative MRI methods have the potential to distinguish and evaluate the complex collection of neurobiological responses to TBI arising from pathology, neuroprotection and recovery. Diffusion MRI provides unique information about the physical environment in tissue and can be used to probe physiological, architectural and microstructural features. While well-established approaches such as diffusion tensor imaging (DTI) are known to be highly sensitive to changes in the tissue environment, more advanced diffusion MRI techniques have been developed that may offer increased specificity or new information for describing abnormalities. These tools are promising, but incompletely understood in the context of TBI. Furthermore, model dependencies and relative limitations may impact the implementation of these approaches and the interpretation of abnormalities in their metrics. The objective of this paper is to present a basic review and comparison across diffusion MRI methods as they pertain to the detection of the most commonly observed tissue and cellular alterations following TBI.

Evaluating corrections for Eddy‐currents and other EPI distortions in diffusion MRI: methodology and a dataset for benchmarking

“…In our experiments, we observed that data corrected only for motion and eddy‐current distortion, but not for EPI distortions, as typically done in major studies, have a median variability higher by 32% for Trace, 15% for FA, and 34% for the primary eigenvector, compared to the EPI corrected data. These findings underscore the importance of including EPI distortion correction to increase the power of diffusion MRI studies, in particular when seeking subtle biological changes, for example those due to mild traumatic brain injury 40,41 …”

Chronic differences in white matter integrity following sport‐related concussion as measured by diffusion MRI: 6‐Month follow‐up

“…This process initiates a cascade of ionic dysregulation and neuroinflammatory processes. Findings of decreased mean diffusivity are likely reflective of cytotoxic edema and inflammation in the acute phase following injury, with a decrease in axial diffusivity likely reflecting axonal damage resulting from cytoskeletal stretching (Hutchinson, Schwerin, Avram, Juliano, & Pierpaoli, 2017) and/or an increase in glial and Schwann cells in the extraaxonal space restricting diffusion parallel to axons (Beaulieu, 2002; Blumbergs et al, 1994; Hutchinson, Avram, et al, 2017; Pasternak et al, 2014). On the other hand, intracellular swelling results in decreased extracellular space within an axon and thus decreased ability for water to permeate through; as such, decreased radial diffusion would be expected.…”

Progression of histopathological and behavioral abnormalities following mild traumatic brain injury in the male ferret

“…To consistently select histologic sections from a similar location relative to the CCI lesion, ex vivo MRI scans were performed prior to sectioning, and regions of abnormal diffusion tensor imaging (DTI) values were identified according to previously described imaging findings along with details of image acquisition and processing (Hutchinson et al, 2016;Hutchinson, Schwerin, Avram, Juliano, & Pierpaoli, 2018 …”