CTA of the ICA bifurcation and intracranial vessels

With multislice CT scanners, CT angiography is increasingly becoming a diagnostic tool for supraaortal (extra- and intracranial) vessel pathology. There are three different fields in which CTA might replace invasive DSA and even compete with MRI techniques. In intracranial aneurysms CTA has a high diagnostic accuracy with a very small number of false negative results. The cutoff aneurysm size is approximately 3 to 4 mm, and nearly 99% of ruptured aneurysms can be recognized by CTA. In ICA stenosis CTA is obviously more accurate than MRA, because it does not have the inherent error of stenosis overestimation and has the additional advantage of visualisation of calcification. Specifically, the latter is a major advantage if one has to decide between stenting and surgical repair of the stenosis. In acute stroke, the combination of tissue and vessel imaging with MR techniques is obviously better than CT technology. However, MR is not always available everywhere. In these cases, the combination of a brain CT and CTA of the supra-aortal vessels might be a good alternative, specifically if thrombolytic therapy is a therapeutic option. In summary, CTA clearly can replace DSA for many diagnostic purposes and will even replace MRA in patients with ICA stenosis.