Magnetic resonance angiography of the intracranial vasculature.

Preliminary experience has shown that MRA can provide useful clinical information that complements the more traditional SE brain evaluation of patients with cerebrovascular disease. MRA is particularly appealing in that it provides a relatively rapid, noninvasive alternative to the existing vascular imaging modalities and the capability to evaluate the brain parenchyma directly. This can often be done without repositioning the patient or significantly prolonging the examination time. MRA sequences have been applied in the evaluation of patients with intracranial aneurysms, vascular malformations, vasoocclusive disease, neoplasms, and dural sinus thrombosis. The MRA study design and acquisition parameters are crucial and need to be optimized to maximize sensitivity and specificity of the examination based on the individual clinical presentation. The results of the SE and MRA studies should be evaluated together to obtain a definitive diagnosis or to determine whether conventional angiography is needed. As with any other diagnostic procedure, it is important to recognize the strengths and limitations of these techniques. Despite its advantages, MRA will not replace conventional catheter angiography in the near future. Rather, it will complement existing indications for conventional MR studies. Spatial resolution and intravascular signal loss due to rapid, complex flow continue to be the most limiting factors in intracranial MRA imaging. Significant improvements in these areas are currently being realized.