Introduction:Cerebrovascular Reactivity (CVR) refers to the response of vessels to vasoactive stimuli. In many disease states CVR is impaired. This results in suboptimal perfusion to brain tissue and increases ischemic risk. Quantitative CVR imaging with Blood Oxygen Level Dependent (BOLD)-fMRI, is a validated neuroimaging technique used to assess ischemic risk: inhaled carbon dioxide is utilized as a vasodilatory stimulus during image acquisition. We aim to demonstrate that Breath-Hold CVR, which utilizes endogenous carbon dioxide (hypercapnia through breath-holding) has a better safety and tolerability profile in children and can provide us with CVR images that are comparable to quantitative techniques.

Methods: In this prospective phased study we examined the validity and reproducibility of BH-CVR in healthy controls. Children (ages 7-18) underwent two CVR studies in the same day: a quantitative study (prospective targeting of end-tidal carbon dioxide with RespriAct^TM) and a Breath-Hold CVR study. Blinded scoring was used to assess the concordance between CVR maps generated. Coefficient of variation of within-day repeat scans was computed in grey and white matter. Cohen’s Kappa analysis was used to assess agreement between whole-brain scores of repeat scans.

Results:Here we present the preliminary results of phase one of our study. Seven healthy children completed the imaging protocol. We report that BH-CVR is feasible, tolerated well, and safe. Interim analyses have shown good repeatability within subjects for BH-CVR. Qualitative scoring showed comparable results between BH-CVR and RespirAct^TMstudies.

Conclusion:Preliminary Data demonstrates that BH-CVR is feasible, tolerable, and comparable to quantitative techniques that have been validated to assess ischemic risk.