Abstract W MP16: Introducing the Imaging the Collaterals in Acute Stroke (iCAS) Multicenter MRI Trial

Abstract

Introduction: imaging Collaterals in Acute Stroke (iCAS) is an NIH-funded, multicenter study to determine if non-contrast arterial spin label (ASL) MRI can characterize collateral flow in patients presenting with acute large vessel stroke and whether it can identify patients who benefit from endovascular therapy. It also enables direct comparison with current state-of-the-art clinical perfusion imaging, bolus perfusion-weighted imaging (PWI). Hypotheses: (1) ASL identifies collaterals with high sensitivity and specificity compared to digital subtraction angiography (DSA). (2) Increasing collateral grade determined by either ASL or DSA is associated with higher CBF. (3) ASL collateral grade independently predicts reduced infarct growth. (4) Patients with a “target mismatch” based on PWI(Tmax>6) can be identified using ASL. (5) Only patients with intermediate grade collaterals will benefit from early reperfusion. Methods: 180 patients will be recruited from up to 6 sites over 5 yrs. Current sites include Stanford, Swedish Hospital Seattle, and UPMC. Inclusion criteria: >18 yrs; NIHSS >=5; planned endovascular therapy (primary or adjuvant therapy following IV tPA); planned MR imaging with ASL & PWI; IA therapy <60 min from MR completion and <12 hrs of symptom onset. Exclusion criteria: mRS>=2 prior to the qualifying stroke; Cr clearance <40 ml/min; contrast allergy; pregnancy; MRI contraindications. MRI will be obtained at 3 time points (<12 hrs, 18-36 hrs later, 5 d), with clinical data at 30 & 90 days. Results: 7 patients have been recruited. While formal image analysis has not been performed, initial review suggests that ASL has similar performance to PWI in this patient population (Fig). Conclusion: It is feasible to acquire ASL during an acute stroke MRI workup, enabling comparison of both collateral measures with DSA and perfusion metrics with PWI. It will provide a framework to account for the crucial role of collaterals in endovascular triage strategy.