Cerebrovascular Reactivity Measurements With High-Density Diffuse Optical Tomography

The purpose of the study protocol is to identify imaging biomarkers for brain tissue under high metabolic stress at risk for permanent injury. We will measure oxygen extraction fraction (OEF) and cerebrovascular reactivity (CVR) in participants with and without perturbations in cerebral oxygen delivery over time to determine each parameter's role in clinical and radiologic neurologic outcomes. Measuring OEF can be done with specialized MRI sequences. Measuring CVR requires a vasoactive response, such as carbon dioxide. In order to deliver carbon dioxide evenly and as safely as possible, we will use RespirACT, an MRI-compatible device, to prevent over-breathing carbon dioxide and allow rapid steady-state physiology to minimize total scan time. We will also use a high density diffuse optical tomography (HD-DOT) cap to assess the measurement of OEF and CVR. This study will investigate both regional OEF and CVR simultaneously to understand each marker's unique developmental trajectory and contribution to stroke risk in children. This work will expand insights into mechanisms of stroke in children and assess the feasibility of the HD-DOT cap for obtaining these insights by comparing a cohort of optical CVR and a cohort of MRI CVR. In addition to the MRI and/or HD-DOT cap with RespirAct, participants may also have their vitals measured, complete cognitive testing, and complete a blood draw with a study visit. Participants may be followed for up to three years and may complete both an MRI scan and an HD-DOT scan within 1 week-12 months of each other. Participants may be invited back to repeat MRI and/or HD-DOT scans 1-2 times over the next three years.