MRA of intracranial aneurysms

Abstract

Most intracranial aneurysms are located in the circle of Willis. They occur in 5-6% of the general population. Patients with intracranial aneurysm either present catastrophically with rupture of the aneurysm have aneurysms that are incidentally discovered. Prognosis is drastically different in each case, with a greater than 50% incidence of death if there is a rupture of the aneurysm. On the other hand, the surgical or endovascular mortality following treatment of an unruptured aneurysm is minimal, with good patient neurological outcome. In the appropriate clinical setting, it is important to find a screening study that can detect a cerebral aneurysm so that definitive cerebral angiography can be performed. The combination of magnetic resonance imaging (MRI) and magnetic resonance angiogram (MRA) can detect an aneurysm in 60-85% of cases. This screening test adds a few minutes of scanning time to the average MR examination. Magnetic resonance angiography techniques continue to improve with better gradients, enhanced sequences to detect flow and reduce flow-related artifacts, shorter echo times with possible use of echo-planar (short scanning time) techniques, and improved imaging matrix, and they may, in conjunction with computed tomographic angiography (CTA), become a reliable non-invasive technique for detection of intracranial aneurysm.