Abstract WP35: An ASL Collateral Score Can Identify Improved Quantitative Cerebral Blood Flow in Acute Stroke Patients

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Objective: To measure quantitative hemodynamic parameters in acute stroke patients using a tomographic collateral assessment based on arterial spin labeling (ASL) [1]. Methods: Patients were retrospectively identified who met these criteria: symptom onset <27 hrs, DWI volume >=10 ml, and ASL and bolus contrast PWI, 1.5T. Pseudocontinuous 3D fast spin echo ASL was performed with the parameters: TR/TE/label time/post-label delay 5500/9.5/1500/2000 ms. PWI was performed using 0.1 mmol Gd and single-shot EPI with the parameters: TR/TE 1800/40 ms. Automated software (RAPID) was used to measure relative CBF, CBV, and time to peak of the residue function (Tmax) [2]. The combined ASL and DSC method was used to determine quantitative CBF and CBV [3]. A four point collateral score (CS) (0=poor, 1=intermediate, 2=good, 3=antegrade perfusion) [4] was determined based on ASL arterial transit artifact (ATA) in 20 ASPECTS ROI’s in each patient [1]. Tests for significant relationships between CS and each parameter was performed. Findings: 13 patients were identified (4 M, 63±13 yrs, 17±7 hrs from symptom onset, DWI size 61±52 ml, PWI Tmax>6 sec size 84±65 ml). CBF increased with increasing CS, with the highest CBF in the antegrade perfused regions. CBV also increased with CS, but there was no difference between good collateral and antegrade regions. Tmax decreased significantly as CS increased. Acute stroke patients with good and poor collaterals are shown in the Figure (yellow arrows = collaterals). Conclusions: Collaterals are important because they supply CBF. ASL is able to predict the quality of collaterals in acute stroke, as was shown previously in Moyamoya disease [1]. This non-contrast assessment of collaterals on MRI may improve patient selection for stroke therapy.