Unsedated cerebrovascular reactivity imaging is well-tolerated in children

Background: Unsedated MRI use in pediatric clinical and research settings is often feasible, but advanced imaging techniques like cerebrovascular reactivity (CVR) may affect tolerability of unsedated MRIs. Exogenous carbon dioxide (CO₂) provides a CVR vasodilatory challenge, but its impact on unsedated children’s MRI tolerability is unknown. Objective: We hypothesized that children would tolerate MRI with exogenous CO₂ as well as children undergoing only MRI. Materials and methods: Children with and without sickle cell disease and/or reactive airway disease participated in prospective, single-site unsedated MRI observational studies and completed a post-scan questionnaire. A RespirAct® device delivered CO₂ during the scan for MRI-measured CVR. Head displacement across frames quantified motion. Tolerability was defined as MRI study completion without lasting symptoms or serious adverse events. Results: One-hundred children participated, with a median age of 14.0 years [11.0, 16.3]. Sickle cell disease and/or reactive airway disease was present in 35% (35/100) and 16% (16/100), respectively. CVR sessions occurred in 75 participants, while 25 had MRI only. All children tolerated and completed the scans; 77% (58/75) had usable CVR data. Motion was similar between those with and without CVR (P=0.33). Children undergoing CVR were more likely to report symptoms, mainly shortness of breath (42/75 vs 3/25; P<0.001), compared to MRI only. Eleven children reported mild, temporary symptoms post-CVR scan; all resolved within a few hours. No serious adverse events occurred. Three children (CVR group) reported unwillingness to repeat the scan. Conclusion: Children tolerate MRI with exogenous CO₂ for CVR measurement with mild, predictable transient symptoms.