Neuroimaging of Stroke and Ischemia in Animal Models

Abstract

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.

Resolvin D2 protects against cerebral ischemia/reperfusion injury in rats

“…Then the brain was quickly removed and frozen in stainless steel brain matrices (− 20 °C) for 10 min, and the cerebellum and olfactory bulb were discarded. As described previously [ 33 ], the ischemic penumbra was dissected. In brief, the brain was sliced into three slices from the anterior tip of the frontal lobe.…”

Importance of Preclinical Research in the Development of Neuroprotective Strategies for Ischemic Stroke

“…Multiple magnetic resonance imaging modalities are applicable to stroke, in particular T2-, diffusion-, and perfusion-weighted imaging for determination of infarct size, location, and penumbra over time. 41 More specialized techniques, such as magnetic resonance spectroscopy for metabolic studies and diffusion tensor imaging for evaluation of white matter damage, allow for specific aspects of ischemic damage and neuroprotection to be evaluated in vivo. 41 The resolution of magnetic resonance imaging is relatively poor, but in vivo 2-photon microscopy has enabled us to examine individual cell and vessel responses to ischemia, as well as provided the means to occlude single arterioles and thereby model very small ischemic strokes.…”

“…41 More specialized techniques, such as magnetic resonance spectroscopy for metabolic studies and diffusion tensor imaging for evaluation of white matter damage, allow for specific aspects of ischemic damage and neuroprotection to be evaluated in vivo. 41 The resolution of magnetic resonance imaging is relatively poor, but in vivo 2-photon microscopy has enabled us to examine individual cell and vessel responses to ischemia, as well as provided the means to occlude single arterioles and thereby model very small ischemic strokes. 42 On a molecular level, transcriptomic, proteomic, and metabolomic approaches have recently been applied in preclinical ischemic stroke to identify either stroke-specific biomarkers or molecular pathways relevant to diagnosis, prognosis, and therapy.…”

Lesion Size- and Location-Dependent Recruitment of Contralesional Thalamus and Motor Cortex Facilitates Recovery after Stroke in Mice

“…White matter damage measured by DTI has been correlated with brain recovery in human and animal studies [12,13]. However, there have been only single applications of in vivo DTI and in vivo fiber tracking in animal models of stroke with no conclusive correlation to neither the behavioral deficit nor the outcome [14,15]. Here, we hypothesized that depending on the stroke size and location, different structurally connected but remote regions undergo secondary neurodegeneration and that distant but functionally connected brain regions are involved in spontaneous recovery of function.…”