Surveillance imaging after intracranial stent implantation: Non-invasive imaging compared with digital subtraction angiography

Background Digital subtraction angiography (DSA) is the gold standard imaging for detection of in-stent restenosis (ISR) but there is limited literature on optimal noninvasive surveillance imaging. In this study, the ability of CT angiography (CTA) and MR angiography (MRA) compared with DSA in recognizing ISR was assessed. Methods A single center database of patients treated with stent implantation for ICAD was accessed. All patients who underwent follow-up imaging with DSA paired with either MRA or CTA within 30 days were included. Two angiography readers and two non-invasive imaging readers measured restenosis with a submillimeter digital caliper. ISR was categorized as: none/minimal, mild (<50%), moderate (≥50-70%) or severe (≥70%). Analysis was performed with weighted k statistics. Results 17 cases of individual stents that underwent surveillance imaging with paired DSA and CTA and five stents with paired DSA and MRA were identified. Of those undergoing DSA and CTA, inter-reader agreement produced k=0.68 (95% CI 0.40 to 0.95) for DSA and k=0.75 (95% CI 0.55 to 0.95) for CTA. Agreement across CTA and DSA was k=0.36 (95% CI 0.26 to 0.52). Of those undergoing DSA and MRA, inter-reader agreement produced k=0.71 (95% CI 0.27 to 1.00) for DSA and k=1.00 (95% CI 1.00 to 1.00) for MRA. Agreement across MRA and DSA was k=0.34 (95% CI 0.18 to 0.51). Conclusions Good inter-reader agreement exists within DSA, CTA and MRA. However, when comparing noninvasive imaging (CTA and MRA) with DSA, only fair agreement exists. These data suggest that CTA and MRA are not comparable to DSA for evaluation of ISR.