Abstract WP68: CT Perfusion Collateral Index in Assessment of Collaterals in Patients With Acute Ischemic Stroke: A New Imaging Biomarker

Abstract

Purpose: Perfusion collateral index (PCI) has been recently defined as a promising measure of collateral flow. We aim to evaluate the collateral status via CT-based PCI in association with outcome measures such as final infraction volume, recanalization status and functional outcome in patients presenting with acute ischemic stroke (AIS) and in a comparative analysis against CTA and DSA collateral scores. Methods: AIS patients with anterior circulation large vessel occlusion who had baseline CTA and CT perfusion and underwent endovascular treatment were included. CTA collateral scores were calculated using modified Tan score and DSA collateral scores were evaluated by ASITN grading. In addition, previously described PCI defined as the volume of moderately hypoperfused tissue (ATD 2-6sec ) multiplied by its corresponding rCBV was calculated in each patient. The association of CTA and DSA collateral scores and PCI were assessed against 3 measured outcomes: 1) Final infarction volume obtained from follow up MRI; 2) Final recanalization status defined by TICI scores; 3) Functional outcome measured by 90-day mRS. Results: A total of 53 patients met inclusion criteria (27F; mean/SD age: 70.1 ± 13 years; median NIHSS: 14). Final infarction volume (mean/SD: 30/40 mL), excellent recanalization defined by TICI >2C was achieved in 36 (68%) patients, and 23 patients (43%) had good functional outcome (mRS <2). Having good collaterals on all 3 modalities (CTA, DSA, CTP-PCI) were associated with significantly (p<0.05) smaller infarction volume. However only good collaterals determined by CTP-PCI was predictive of achieving excellent recanalization (p=0.001) or good functional outcome (p=0.01) ( Figure 1 ). Conclusion: Collateral status assessed via CT-PCI outperforms CTA and DSA collateral scores in prediction of excellent recanalization and good functional outcome and may be a promising imaging biomarker of collateral status in patients with AIS.