Simultaneous fPET and fMRI for Assessing Dynamic Neurovascular and Neurometabolic Changes

Purpose BOLD fMRI has been used extensively in neuroscience research. However, BOLD fMRI probes neural activity indirectly and the signal reflects a composite change of neurovascular (hemodynamic responses) and neurometabolic (aerobic or anaerobic glucose metabolism) coupling. Neuronal activations primarily engage oxidative phosphorylation are more difficult to be detected by BOLD fMRI than those involve more glycolysis if the same amount of glucoses are being consumed. Therefore, it has been suggested that measurements of hemodynamics and oxygen and glucose consumptions are required to better interpret function responses in tasks and diseases. Conventional FDG PET studies can only infer changes in glucose utilization by state-contrast experiments and did not measure metabolism in a truly dynamic manner. In this study, we reinvent the use FDG PET by controlling the delivery of radiotracer to enable a truly dynamic detection of glucose metabolism, a technique we termed functional PET (fPET). In conjunction with simultaneously acquired BOLD/CBF fMRI, a wealth of information was obtained in one scan. Our novel imaging approach enables a more complete view to interpret changes in brain function than by using either FDG PET or BOLD fMRI alone. We first develop the imaging methods and then carry out simultaneous fPET/fMRI scans under different physiological conditions to validate our approaches.