Clinical use of nuclear magnetic resonance imaging in stroke.

There are many positive aspects to the use of MRI in the evaluation of cerebrovascular disease. First, the MR imaging technique appears to be essentially without hazard. It does not rely on ionizing radiation, and no intravenous injections of contrast agent are necessary. MRI exploits the tissue's inherent biophysical characteristics to provide superior contrast. Infarctions are well delineated by MRI, often better and earlier than CT. Because of the lack of MRI signal from bone and thus the lack of transverse artifact from bone often seen with CT, lesions in the posterior fossa are very well visualized. With MRI it is possible to obtain images in the transverse, coronal, and sagittal planes, which provides for good evaluation of lesion size and extent. Arteriovenous malformations have been visualized by MRI, but it is still too early to know whether MRI has any detection capability over CT in this disorder. Subdural hematomas have been well visualized by MRI, including cases of isodense subdurals not visualized by CT. On the other hand, MRI has not proven to have any advantage over CT in the evaluation of intracerebral hemorrhage, hemorrhagic infarction, and subarachnoid hemorrhage. In fact, for detection of intracerebral hemorrhage and subarachnoid hemorrhage, CT may be better at the present time. In chronic infarction the surrounding area of Wallerian degeneration may cause the area of infarction to appear larger than it actually is. Hopefully, with further research into the use of different pulse sequence techniques and with good neuropathological correlation, the present limitations of MRI can be eliminated.(ABSTRACT TRUNCATED AT 250 WORDS)