Comparison of Computed Tomography Angiography With Digital Subtraction Angiography in the Assessment of Clipped Intracranial Aneurysms

Purpose: To examine whether computed tomography angiography (CTA) is comparable to digital subtraction angiography (DSA) in assessing clipped intracranial aneurysms. Materials and Methods: Retrospective collection of clipped aneurysms that had both CTA and DSA within 2 months of one another. Computed tomography angiograms were independently reviewed by 2 blinded neuroradiologists; rereviewed by one at least 4 months later. Each was classified as complete obliteration, neck remnant, or residual aneurysm. Parent vessel was classified as patent or occluded. Digital subtraction angiograms were reviewed in a similar manner by a third blinded neuroradiologist. Results: Forty-eight patients with 53 clipped aneurysms were collected. On DSA, 35 were completely obliterated, 10 neck remnants, and 8 residual aneurysms. The ability of CTA to detect residual aneurysms versus complete obliterations or neck remnants was excellent (mean sensitivity, 88%; specificity, 100%; positive predictive value [PPV], 100%; negative predictive value [NPV], 98%). The ability of CTA to detect neck remnants versus complete obliterations was poor (mean sensitivity, 20%; specificity, 99%; PPV, 83%; NPV, 81%). The CTAs were good at detecting parent vessel occlusion (mean sensitivity, 88%; specificity, 97%; PPV, 75%; NPV, 99%). Interrater and intrarater agreement was good to excellent for aneurysm and parent vessel assessment, with kappa values ranging from 0.6 to 1.0. Conclusions: Computed tomography angiography has high sensitivity and specificity for residual aneurysm detection and parent vessel occlusion. It is not accurate in neck remnant detection, although these were small and of uncertain clinical significance. This suggests that CTA is useful for follow-up of clipped aneurysms. However, given the potential to miss neck remnants or small residual aneurysms, it is recommended to perform initial DSA and CTA to select cases in which CTA follow-up is appropriate.