MRI in the Study of Animal Models of Stroke

Stroke consists of the loss of cerebral functions resulting from the interruption of blood supply to a region of the brain, and represents the second cause of death and the leading cause of major disability in adults in Europe. Stroke is a very active field of research at preclinical and clinical levels, and Magnetic Resonance Imaging (MRI) is one of the most powerful tools that scientist and clinicians have for the study of the onset, evolution and consequences of this devastating disease, as well as for the monitoring of the success of available treatments, or for the development of novel therapeutic strategies.MRI can tackle the study of stroke from different points of view, and at scales ranging from subcellular to systems biology level. Magnetic resonance spectroscopy (MRS) allows the noninvasive measurement of the levels of principal metabolites in the brain, and how they change during the course of the disease, or in response to therapy. Glutamate, in particular, is very important in the field of stroke. Several anatomical MR techniques allow the characterization of the lesion volumes, the formation of cytotoxic and vasogenic edema, changes in cerebral blood flow and volume, structural changes in gray and white matter, the obtaining of the vascular architecture and status, etc. At functional level, diverse modalities of functional MRI (fMRI) allow the assessment of the alteration in the function and organization of neuronal networks of the subject under study, as a consequence of the disease or in response to treatment. Finally, emerging imaging modalities that include temperature and pH mapping of the brain, imaging by chemical exchange saturation transfer effect (CEST), all of them closely related to tissue status, or the use of contrast agents for the targeting of tissue in theranostic approaches or for cell tracking studies in cell-based therapies, etc., are only a few examples of the power and versatility of MRI as a definitive tool for the study of stroke.In this work we will set our focus on preclinical imaging of stroke models, emphasizing the most commonly used imaging modalities in a stroke-dedicated research laboratory. However, advanced techniques will be briefly discussed, providing references to specialized literature for more advanced readers. Thus, the aim of this chapter consist in the description of a simple imaging protocol for the study of the most important and common aspects of stroke in a research laboratory.