Abstract 6913: Measuring Cerebrovascular Reactivity in Moyamoya Disease: Insights from Simultaneous PET/MRI

Abstract

Introduction: Cerebrovascular reactivity (CVR) reflects the change in cerebral blood flow (CBF) in response to a vasoactive stimulus. Studies have demonstrated that impaired CVR was associated with a higher risk of stroke. PET imaging with 15 O-water as the radiotracer has been the standard modality to measure CBF and CVR. But it is impractical in most hospitals due to the requirement of an on-site cyclotron. Arterial spin labeling is a quantitative MRI technique that enables non-invasive CBF and CVR measurement. Hypothesis: ASL with multiple delays was more accurate than with single delay, using 15 O-water PET as the reference. Methods: Data were collected from 26 Moyamoya patients (18-64 years, 16 females) using a simultaneous 3T PET/MRI system (GE SIGNA, Waukesha, WI, USA). All patients had unilateral or bilateral vessel occlusion at the anterior cerebral artery (ACA), middle cerebral artery (MCA), and/or posterior cerebral artery (PCA). Imaging data were acquired using single post-labeling delay pseudo-continuous ASL (single-PLD PCASL), delay pseudo-continuous ASL (multi-PLD PCASL, 3 PLDs), and 15 O-water PET simultaneously at baseline and 15 minutes after the injection of the vasodilator acetazolamide (15 mg/kg with a maximum of 1 g). CBF of PET was computed using the single-compartment pharmacokinetic model; CBF of ASL was computed using the general kinetic model. CVR was computed as the percentage of CBF change compared with baseline CBF. Paired t-tests were performed to compare the mean CVR between the affected and unaffected territories. Results: Our quantitative analysis showed that the CVR of the affected regions was significantly lower than the normal regions (by 68%, 52%, and 56% for PET, single-PLD PCASL, and multi-PLD PCASL respectively). Conclusions: Both single and multi-delay ASL were effective in detecting impaired CVR in Moyamoya patients.