The performance and capabilities of magnetic resonance imaging (MRI) equipment have recently been greatly improved by innovations to both the hardware (e.g., magnets, gradients and coils) and software (e.g., image acquisition sequences and data processing). These enhancements have made MRI more powerful and versatile than previously. This progress has translated into beneficial reductions in the overall examination times with regard to static imaging studies that are essential for primary diagnosis, and also the practical implementation of functional imaging, offering the promise of an increase the diagnostic power of MRI in terms of both sensitivity and specificity. These functional studies are increasingly being used together with conventional MR to obtain a more complete pathophysiological and prognostic picture of the CNS pathology in question. In addition, these MR techniques provide information on the movement of water molecules caused by thermal agitation (i.e., diffusion), microvascular haemodynamics (i.e., perfusion) and cerebral metabolism (i.e., spectroscopy). In cases of cerebrovascular disease, these types of examinations permit very early and accurate diagnosis, and are capble of indicating the optimal treatment programme to be adopted (9). In addition to detecting irreversibly damaged tissue, they also point out areas at risk of infarction that could benefit from further treatment. In the particular case of hyperacute cerebral ischaemia, in which conventional T2- weighted MRI can be negative or ambiguous (1), diffusion weighted imaging is nearly always positive, clearly revealing the areas of infarction. Surrounding the ischaemic core, most cerebral infarctions also include a peripheral zone that is ischaemic but uninfarcted, the socalled ischaemic penumbra, which could potentially progress to frank infarction; this penumbra can be distinguished using perfusion MRI and/or spectroscopy. The information obtained using such techniques can be expressed with qualitative data in the form of variations in MR signal intensity, or with quantitative data, thus making it possible to interpret the results in a somewhat unbiased manner, irrespective of the reader.
ASJC Scopus subject areas