Intravenous digital substraction angiography of the nearly occluded internal carotid artery

Three patients with nearly occluded internal carotid artery origins were evaluated with intravenous digital subtraction angiography and subsequently had sucesssful carotid endarterectomies. The angiographic features are described. Although conventional arterial angiography offers superior spatial resolution and selectivity, the thorough mixing of blood and contrast medium that occurs with the intravenous technique minimizes the tendency toward layering beyond a high-grade stenosis, which may occur with selective arterial injection. In cooperative patients, the intravenous digital technique may be sufficiently reliable in the detection of the nearly occluded internal carotid artery to obviate conventional selective common carotid angiography.