MR angiography (MRA) shows arterial stenosis intracranially and extracranially, and excludes large aneurysms and vascular malformations. It is a good screening tool.

Recent data indicate that contrast-enhanced MRA might  be the most reliable of non-invasive tests. In our hands, carotid ultrasound is better at estimating the degree of internal carotid artery (ICA) stenosis at the bifurcation. TCD complements other vascular imaging and can also be used to follow changes over time.

You will often focus on the origins of the internal carotid arteries, but do not forget the vertebral artery origins and intracranial arteries that often harbor atherosclerotic narrowing which may be the etiology of the stroke.

Digital subtraction angiography (DSA) is considered the gold standard for visualizing the arteries, but is not without risk. CT angiography can give you sufficient detail and can be done quickly from the ED.

DSA often takes much longer to obtain due to the need to organize the angiography team. For determining degree of arterial stenoses, seeing arterial dissection, or other vascular abnormalities, however, DSA is still considered the gold standard.