Feasibility and precision of cerebral blood flow and cerebrovascular reactivity MRI measurements using a computer-controlled gas delivery system in an anesthetised juvenile animal model.

Objective: To demonstrate the feasibility and repeatability of cerebrovascular reactivity (CVR) imaging using a controlled CO(2) challenge in mechanically ventilated juvenile pigs.

Methods: Precise end-tidal partial pressure CO(2) (PETCO(2)) control was achieved via a computer-controlled model-driven prospective end-tidal targeting (MPET) system integrated with mechanical ventilation using a custom-built secondary breathing circuit. Test-retest blood-oxygen level dependent (BOLD) CVR images were collected in nine juvenile pigs by quantifying the BOLD response to iso-oxic square-wave PETCO(2) changes. For comparison, test-retest baseline arterial spin labeling (ASL) cerebral blood flow (CBF) images were collected. Repeatability was quantified using the intra-class correlation coefficient (ICC) and coefficient of variation (CV).

Results: The repeatability of the PETCO(2) (CV < 2%) step changes resulted in BOLD CVR ICC > 0.94 and CV < 6% for cortical brain regions, which was similar to ASL CBF repeatability (ICC > 0.96 and CV < 4%).

Conclusions: This study demonstrates the feasibility and precision of CVR imaging with an MPET CO(2) challenge in mechanically ventilated subjects using an animal model. Translation of this method into clinical imaging protocols may enable CVR imaging in young children with cerebrovascular disease who require general anesthesia.