A Hybrid PET/MRI Brain Connectivity Approach for Improving Epilepsy Surgical Evaluation
Abstract
Hybrid PET/MRI can non-invasively improve epileptic focus (EF) localization prior to surgical resection in drug-resistant epilepsy (DRE), especially when MRI is negative. In this thesis, we developed an 18F-fluorodeoxyglucose (FDG) PET-guided diffusion tractography (PET/DTI) approach to assess white matter (WM) integrity in MRI-negative DRE and evaluated its potential impact on epilepsy surgical planning. To validate the potential of PET/MRI, we first evaluated the diagnostic competence of PET/MRI in DRE and found that PET/MRI provides similar diagnostic information as PET/CT (current clinical standard). For the PET/DTI approach, we used asymmetry index (AI) mapping of FDG-PET to guide WM fiber tractography around glucose hypometabolic brain regions (potential EF). Fiber tractography was repeated in the contralateral brain region (opposite to EF), which served as a control for this study. WM fibers were quantified by calculating the fiber count, mean fractional anisotropy (FA), mean fiber length, and mean cross-section of each fiber bundle. WM integrity was assessed through fiber visualization and by normalizing ipsilateral fiber measurements to contralateral fiber measurements. The added value of PET/DTI in clinical decision-making was assessed by an experienced epileptologist. In over 60% of the patient cohort (n = 14), AI mapping findings were concordant with clinical reports on seizure-onset zone. Mean FA, fiber count, and mean fiber length were decreased in 14/14 (100%), 13/14 (93%), and 12/14 (86%) patients, respectively. PET/DTI improved diagnostic confidence in 10/14 (71%) patients and indicated surgical candidacy be reassessed in 3/6 (50%) patients who had not undergone surgery. FDG-PET coupled with diffusion tractography can be a powerful tool for detecting EF and assessing WM integrity around EF in MRI-negative epilepsy. PET/DTI could further enhance clinical decision-making in epilepsy surgery.