Intracranial magnetic resonance imaging.

Magnetic resonance angiography (MRA) is currently being incorporated into the routine MR evaluations of patients with suspected cerebrovascular disease. Currently, MRA serves as a useful adjunct to routine parenchymal spin-echo imaging of the head. Intracranial MRA is predominantly used as a screening test for cerebrovascular disease in situations where the clinical suspicion and/or the patient's physical condition does not warrant a conventional arteriogram. Clinical experience to date suggests that MRA can play a significant role in the evaluation of patients with suspected intracranial aneurysms, arteriovenous fistulae, large vessel occlusive disease, and dural sinus occlusion/thrombosis. MRA has not yet reached the point where it can replace conventional catheter angiography. This is most apparent when trying to evaluate 1) larger vessels which are typically difficult to visualize due to higher order motion terms (eg, carotid siphon); 2) the smaller cortical branches with relatively slow flow that would be necessary to see in patients with suspected vasculitis; and 3) any situation in which dynamic information is important such as with mass lesions or vascular malformations. These limitations must be taken into account when deciding on the appropriate imaging study for an individual patient. Large-scale, well-controlled prospective clinical trials will ultimately determine the role intracranial MRA will play in the evaluation of patients with suspected cerebrovascular disease.