Dynamic changes in the cerebral metabolic rate of o 2 and oxygen extraction ratio in event-related functional MRI

Abstract

Dynamic changes in the cerebral metabolic rate of oxygen (CMRO 2) and oxygen extraction ratio (OER) in an event-related functional MRI (ER-fMRI) were measured in this study. Six subjects participated in this study at a magnetic field of 1.9 T. Cerebral blood flow (CBF) and blood oxygenation level-dependent (BOLD) changes were acquired during the brief visual stimulation, and the corresponding changes in CMRO 2 and OER were then determined. The results showed that the maximum relative changes in CMRO 2 and OER were about 10.36 ± 0.85 and −6.54 ± 0.55%, respectively, while the maximum changes in CBF and BOLD were approximately 17.35 ± 1.37 and 1.03 ± 0.06%, respectively. The CBF, CMRO 2, and OER changes reach their maximum approximately 1 s earlier than the BOLD signal change (4.15 ± 0.21, 4.16 ± 0.21, and 4.17 ± 0.21 s vs 5.12 ± 0.24 s after stimulation, P < 0.05).