Angiographic Computed Tomography for Imaging of Underdeployed Intracranial Stent
A 77-year-old woman presented with a transient ischemic attack. Cerebral angiography showed occlusion of the supraclinoid segment of the right internal carotid artery, a persistent trigeminal artery, and an 80% stenosis of the cavernous segment of the internal carotid artery. After deployment of a 3 mm ×13 mm, balloon-expandable stent (Bx SONIC, Cordis, Miami Lakes, Fla), a control angiogram demonstrated a residual stenosis, which remained even after repeated balloon inflation. An underlying calcification was assumed. (Figure, A). Although the patient had remained asymptomatic since initial treatment, the angiographic follow-up after 6 months showed a significant in-stent restenosis (Figure, B). Nonsubtracted images could not provide sufficient diagnostic information about the stent itself because of sphenoid osseous structures adjacent and surrounding the cavernous carotid artery (Figure, C and D).
A non–contrast-enhanced angiographic computed tomogram, using a rotating C-arm with a newly available flat panel detector (Axiom Artis dBA [DynaCT], Siemens Medical Solutions, Erlangen, Germany), was performed by using the following parameters: 20-second rotation, increment of 0.4°, 538 projections, 512×512 matrix). It revealed that the stent was underdeployed as the result of a heavily calcified circumferential plaque (Figure, E and F). Multiplanar reconstructions in orthogonal (“down-the-barrel”) views demonstrated not only the different diameters within the stent lumen but also that the plaque consisted of a calcified (hard) and a noncalcified (soft) portion (Figure, G and H). Detection of stent underdeployment or asymmetric deployment, a potential major factor for development of in-stent restenosis, is a diagnostic dilemma in intracranial stenting. In particular, in the petrous, cavernous, and paraclinoid carotid artery as well as in the distal vertebral or proximal basilar artery, where overlying bony structures impair significantly radiographic visualization of small stents, diagnostic information obtained through the use of conventional imaging techniques is currently insufficient.
Because of the high contrast and spatial resolution of modern flat-panel detector systems, angiographic computed tomography provides 3-dimensional images in excellent quality, adding valuable diagnostic information to digital subtraction angiography or digital radiography while the patient is still on the table.1,2 This promising new technique may play a major role in future diagnostic imaging of the stenting procedure as well as of follow-up studies.
The online-only Data Supplement, which contains a movie, can be found at http://circ.ahajournals.org/cgi/content/full/114/12/e499/DC1.