Abstracts

Rationale: Assessment of brain metabolism is often a critical step in the presurgical assessment of patients with drug resistant epilepsy. Existing techniques such as FDG-PET and MRSI have limitations including cost, radiation exposure, availability, and limited spatial resolution. We investigated the use of a novel MRI technique to map brain metabolism in participants with drug resistant epilepsy who had been previously noted to have regional hypometabolism on interictal FDG-PET. Methods: Participants underwent quantitative dynamic-contrast-enhanced (DCE) MRI at 3T using 0.1 mmol/kg Gadoteridol. Shutter-speed model (SSM) analysis yielded the mean capillary water molecule lifetime (tau b), a parameter associated with Na+/K+ ATPase activity and a putative surrogate measure of brain metabolism. FDG-PET images were spatially co-registered to DCE-MRI. Associations between FDG-PET and (tau b) from 27 atlas-defined bilateral brain regions were assessed. Results: We studied 5 subjects with drug resistant epilepsy. DCE-MRI time series data were acquired with full brain coverage and high spatial and temporal resolution over 10 minutes total for the time-series acquisition. DCE-MRI image quality was excellent in the temporal lobes and throughout the brain. Overall, FDG-PET activity was negatively correlated with (tau b), with correlation coefficients that ranged from -0.59 to -0.84 (mean(SD): 0.70 (0.11). Results from a representative subject are shown in figure 1. Conclusions: Quantitative SSM DCE-MRI is feasible in epilepsy patients. The technique yields a measure of brain metabolism (tau b) that is strongly associated with FDG-PET uptake. Spatial resolution of the MRI technique is an order of magnitude greater than FDG-PET or MRSI, substantially reducing partial volume effect confounds. The DCE-MRI technique is easily added to routine anatomical MRI sequences without the need for special hardware. The findings from this pilot work provide preliminary evidence for this novel MRI technique as an alternative measure of brain metabolism in drug resistant epilepsy. Funding: This pilot work was supported by the OHSU School of Medicine Faculty Innovation Fund.