Quantifying the Artefacts Caused by Hyperoxic Challenges

Ian Driver¹, Jack Harmer¹, Emma Hall¹, Susan Pritchard¹, Susan Francis¹, Penny Gowland¹

Increased oxygen in the oral cavity and sinuses during hyperoxia causes local changes in magnetic field homogeneity. This study dynamically maps these field changes, and quantifies the hyperoxia-induced frequency shift in the frontal sinus, as well as more distant brain regions of most interest to studies using hyperoxia for cerebral blood volume estimation and BOLD calibration. A hyperoxia challenge was found to induce a ~ 20 Hz shift close to the sinus, away from this region this reduced, but not to zero. Although not significantly affecting transverse relaxation, hyperoxia will modulate EPI distortions, an effect that should be dynamically monitored.