RAPID perfusion CT in acute ischemic stroke: an educational pictorial review of common patterns, pearls, and pitfalls.

Rapid processing of Perfusion and Diffusion (RAPID) software for CT perfusion (CTP) is a valuable tool for the evaluation of acute ischemic stroke and therapeutic decision-making in extended therapeutic windows. However, automated maps should not be interpreted in isolation. A structured, pattern-based approach, integrating qualitative visual assessment with automated quantitative output and clinical information to refine therapeutic selection, remains essential to mitigate pitfalls and optimize patient care. The aim of this article is to provide an educational pictorial review based on selected illustrative cases of the most common imaging patterns, interpretive pitfalls, and technical features of CTP processed with RAPID software in acute ischemic stroke, that may serve as a practical guide for radiologists and neuroradiologists. KEY POINTS: Question How can radiologists effectively interpret automated RAPID CT perfusion maps in acute ischemic stroke while avoiding common technical traps, diagnostic pitfalls, and anatomical limitations? Findings Integrating qualitative visual assessment, quantitative RAPID outputs, and clinical-vascular data within a structured workflow minimizes diagnostic errors and optimizes patient selection for reperfusion. Critical relevance statement This educational pictorial review provides a practical, pattern-based approach to RAPID CT perfusion interpretation, highlighting clinical applications, technical limitations, software variability, and diagnostic pitfalls to advance everyday neuroradiological practice and personalized stroke management.