Neuroimaging of stroke and ischemia in animal models.

Magnetic resonance imaging (MRI) has dramatically changed our ability to diagnose and treat stroke as well as follow its evolution and response to treatment. Early stroke and ischemia can be visualized using diffusion-weighted imaging that utilizes water diffusion within tissues as a reporter for evolving neuropathology that reflects cytotoxic edema, particularly during the first several days after injury. T2-weighted imaging is used for evaluation of vasogenic edema but also is a reliable indicator of the volume and regional distribution of injured tissues. Perfusion-weighted imaging can be used to assess vascular function and also to evaluate potential tissues that might be rescued using therapeutic interventions (core vs. penumbra). Other imaging modalities such as magnetic resonance spectroscopy, diffusion tensor imaging, and susceptibility-weighted imaging are also being used to assist in rapid diagnosis of injured tissues following stroke. While visual analysis of MR data can provide some information about the evolution of injury, quantitative analyses allow definitive and objective evaluations of the injury and could be used to assess novel therapeutic strategies. We review here the basic uses of neuroimaging, focusing on MR approaches to assess stroke and ischemic injury in animal models.

Diffusion-weighted magnetic resonance imaging improves outcome prediction in adult traumatic brain injury.

In patients with traumatic brain injury (TBI), diffuse axonal injury (DAI) accounts for a significant amount of parenchymal injury. Diffusion weighted magnetic resonance imaging (DWI) is known to be sensitive for detecting visible DAI lesions. We focused on detection of non-visible, quantifiable diffusion changes in specific normal-appearing brain regions, using apparent diffusion coefficient (ADC) maps. Thirty-seven adults with TBI were compared to 35 age-matched control patients. DWI was performed and ADC maps were generated. Thirty-one regions of interest (ROI) were manually drawn on ADC maps and ADC values extracted. Brain ROIs were categorized into five zones: peripheral gray matter, peripheral white matter, deep gray matter, deep white matter, and posterior fossa. ADC results were compared with the severity of injury based on the admission Glasgow Coma Scale (GCS 3-8; severe; GSC 9-15 mild/moderate) and with long-term outcome (6-12 months after injury) using the Glasgow Outcome Scale (GOS 1-3, unfavorable; GOS: 4-5, favorable) score. Mean ADC values in all five brain zones were significantly different between TBI subjects and controls (p