PREDICTIVE VALUE OF CT PERFUSION IMAGING IN ACUTE ISCHEMIC STROKE PATIENTS PRESENTING IN LATE WINDOW PERIOD.

Background: Acute ischemic stroke is a time-critical medical emergency and a major global cause of morbidity and mortality. Timely identification of salvageable brain tissue in the late therapeutic window remains a clinical challenge. While MRI remains the gold standard, its limited availability and contraindications in certain patients have highlighted the role of computed tomography perfusion (CTP) as a rapid and accessible alternative for guiding treatment in hyperacute stroke. Objective: To determine the predictive value of CT perfusion imaging in patients presenting with acute ischemic stroke beyond the standard thrombolysis window. Methods: This prospective cohort study was conducted at the Armed Forces Institute of Radiology and Imaging (AFIRI), Rawalpindi, from March 2023 to September 2023. A total of 100 patients aged 30–70 years, presenting in the late window period with clinical suspicion of acute ischemic stroke, were included through non-probability convenience sampling. Each patient underwent a non-contrast CT followed by CT perfusion. All scans were independently interpreted by a consultant radiologist with over seven years of experience. The predictive value, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CT perfusion for detecting acute infarction were calculated using standard 2×2 diagnostic accuracy analysis. Results: Of the 100 patients, 56% were male and 44% female. CT perfusion detected acute ischemic infarction in 88 cases, resulting in a predictive value of 88%. The sensitivity was 91.4%, specificity 66.6%, PPV 97.7%, and NPV 33.3%. Conclusion: CT perfusion imaging demonstrates high sensitivity and diagnostic yield in identifying acute ischemic stroke during the late window period, making it a valuable tool in emergency stroke evaluation and therapeutic decision-making.