Chemical Exchange Saturation Transfer-Based Functional Magnetic Resonance Imaging (CEST-fMRI) in the Human Brain at 3T

Motivation: Conventional fMRI techniques indirectly map neural activity through the BOLD effect, but there is a need for a methodology to directly detect dynamic changes in neurotransmitter levels. Goal(s): Our goal was to detect the increase in glutamate concentration in the human brain during a visual task based on CEST. Approach: We performed two tailored experiments on a 3T scanner and used a 4-regressor general linear model (GLM) analysis to extract the metabolite effects from CEST-fMRI signals. Results: A ~0.12% metabolite effect was detected at glutamate-proximal frequency offsets, consistent with our simulation under a 3% increase in glutamate concentrations during brain activity. Impact: Our study successfully revealed the mechanism behind CEST-fMRI and demonstrated its ability to detect dynamic changes in glutamate concentrations during visual stimulation. The CEST-fMRI methodology enables the investigation of neurotransmitter changes, potentially becoming an imaging modality that guides neuroscience research.