Additional value of CTP maps in occlusion detection on CTP angiographic reconstructions for ischemic stroke

Background: CT perfusion angiographic reconstructions (CTP-AR), derived at the peak arterial inflow, have demonstrated similar diagnostic accuracy to CTA for occlusion detection in the anterior circulation. Colour-coded CTP maps may aid in localizing an occlusion. This study aim to assess the additional value of CTP maps for occlusion detection in ischemic stroke patients assessed with CTA or CTP-AR. Methods: In this single center retrospective study, ischemic stroke patients who underwent both CTA and CTP from September 2020 up to and including September 2021 were included. The 1 mm CTP series at peak arterial inflow corresponds to the CTP-AR. Following the initial assessment of CTA and CTP-AR for occlusion detection, three readers with varying levels of experienced, reassessed the CTA and CTP-AR with access to the color-coded CTP maps. Each CTA and CTP-AR was reviewed by two readers, and certainty of assessment was recorded. The reference standard was determined through a consensus meeting. Differences in certainty were assessed using a t-test for paired samples. Results: Out of 210 patients, 107 patients had an occlusion based on our reference standard. The addition of CTP maps resulted in the finding of 11 (2.6%) additional occlusions out of 420 CTA readings and 9 (2.1%) out of 420 CTP-AR readings, primarily involving distal occlusions. After addition of CTP maps, 7 (1.6%) initial assessments on CTA and 3 (0.7%) initial assessments on CTP-AR were deemed false positive. The overall certainty of all readers significantly (P < 0.001) increased after addition of CTP maps. Conclusion: The usage of CTP maps improved occlusion detection on both CTA and CTP-AR, especially for distal occlusions, and resulted in the increase of the overall level of certainty among readers with varying levels of experience.