Advanced neuroimaging of mild traumatic brain injury

Mild traumatic brain injury (mTBI) constitutes the majority of brain trauma cases. Despite its prevalence, detection in clinical imaging remains a challenge as does the ability to predict duration and extent of disability. Advanced magnetic resonance imaging (MRI) methods combined with improved data analytic techniques have already demonstrated the potential to meet this challenge. This chapter reviews the recent progress in detection and outcome prediction in mTBI using the latest MRI techniques, including diffusion tensor imaging (DTI) and susceptibility-weighted imaging and mapping (SWI and SWIM), among others. In DTI investigations, several recent published reports have found that DTI is sensitive to alterations in white matter microstructure, not revealed by conventional MRI. More specifically, DTI reveals alterations in the microstructure of white matter axons caused by traumatic shear and stretch, which have been shown to correlate with clinical severity indicators and neuropsychological deficits. It can also demonstrate large-scale brain network changes after injury. In SWI/SWIM research, by virtue of its excellent sensitivity to iron and deoxygenated hemoglobin, SWI/SWIM has demonstrated exquisite detection of microhemorrhages and further quantification of hemorrhage and blood oxygenation. Used together, these advanced imaging techniques have the potential to serve as a set of surrogate biomarkers which can be used in determining prognosis and will likely have a major role in animal and human therapeutic trials, both to improve selection criteria of experimental subjects and to provide a number of new biomarkers to follow, in addition to conventional clinical and behavioral measures.