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(Stroke. 2008;39:1184.)
© 2008 American Heart Association, Inc.

Original Contributions

How Accurate Is CT Angiography in Evaluating Intracranial Atherosclerotic Disease?

Mai N. Nguyen-Huynh, MD; Max Wintermark, MD; Joey English, MD, PhD; Jack Lam, MD; Eric Vittinghoff, PhD; Wade S. Smith, MD, PhD S. Claiborne Johnston, MD, PhD

From the Departments of Neurology (M.N.N.-H., J.E., J.L., W.S.S., S.C.J.), Epidemiology (S.C.J.), Biostatistics (E.V.), and Neuroradiology (M.W.), University of California, San Francisco.

Correspondence to Mai N. Nguyen-Huynh, MD, UCSF Neurology, Box 0114, 505 Parnassus Avenue, M-798, San Francisco, CA 94143-0114. E-mail mai.nguyen-huynh{at}ucsfmedctr.org

Background and Purpose— Digital subtraction angiography (DSA) is regarded as the gold standard in assessing degree of stenosis in intracranial vessels. However, it is invasive and can only be carried out at specialized centers. We sought to compare CT angiography (CTA) to DSA for detection and measurement of stenosis in large intracranial arteries.

Methods— -We identified all subjects admitted with ischemic stroke or transient ischemic attack and with CTA and DSA studies of good quality completed within 30 days of each other between April 2000 and May 2006 at a single medical center. Two readers blinded to clinical information reviewed each CTA and DSA independently. Each reader located and measured stenosis of 15 prespecified large intracranial arterial segments per study at the same level of magnification. These stenotic lesions were most likely atherosclerotic in etiology. All measurements were made with Wiha digiMax 6" digital calipers. The degree of stenosis was calculated using the published method for the Warfarin-Aspirin Symptomatic Intracranial Disease study. All disagreements of greater than 10% were reviewed by a third reader who decided between the 2 prior measurements. Segments were excluded from analyses if they were judged to be congenitally hypoplastic or seen only through collaterals or cross-filling. Intraclass correlation, sensitivity, and specificity were calculated using DSA as the reference standard.

Results— Forty-one pairs of CTA and DSAs from 41 patients were reviewed. CTAs were completed within 28 days before 13 days after DSA, with a median of 1 day. A total of 475 pairs of major intracranial arterial segment were analyzed. Intraclass correlation between degree of stenosis based on CTA and DSA for all segments was 0.98 (P=0.001). CTA detected large arterial occlusion with 100% sensitivity and specificity. For detection of 50% stenosis, CTA had 97.1% sensitivity and 99.5% specificity. To detect all lesions 50% as determined by DSA, the cut off point on CTA appeared to be at 30%, with a false-positive rate of 2.4%.

Conclusions— Compared to DSA, CTA has high sensitivity and specificity for detecting 50% stenosis of large intracranial arterial segments. CTA is minimally invasive and may be a useful screening tool for intracranial arterial disease and occlusion.

Key Words: digital subtraction angiography • CT angiography • intracranial arteriosclerosis • neuroradiology