First implementation of dynamic oxygen-17 (¹⁷O) magnetic resonance imaging at 7 Tesla during neuronal stimulation in...

First implementation of dynamic oxygen-17 (¹⁷O) MRI at 7 Tesla (T) during neuronal stimulation in the human brain.

Five healthy volunteers underwent a three-phase ¹⁷O gas (¹⁷O₂) inhalation experiment. Combined right-side visual stimulus and right-hand finger tapping were used to achieve neuronal stimulation in the left cerebral hemisphere. Data analysis included the evaluation of the relative partial volume (PV)-corrected time evolution of absolute ¹⁷O water (H₂¹⁷O) concentration and of the relative signal evolution without PV correction. Statistical analysis was performed using a one-tailed paired t test. Blood oxygen level-dependent (BOLD) experiments were performed to validate the stimulation paradigm.

The BOLD maps showed significant activity in the stimulated left visual and sensorimotor cortex compared to the non-stimulated right side. PV correction of ¹⁷O MR data resulted in high signal fluctuations with a noise level of 10% due to small regions of interest (ROI), impeding further quantitative analysis. Statistical evaluation of the relative H₂¹⁷O signal with PV correction (p = 0.168) and without (p = 0.382) did not show significant difference between the stimulated left and non-stimulated right sensorimotor ROI.

The change of cerebral oxygen metabolism induced by sensorimotor and visual stimulation is not large enough to be reliably detected with the current setup and methodology of dynamic ¹⁷O MRI at 7 T.