Improved 3D EPI for Pre-Surgical Mapping of Epilepsy

Project Summary In pediatric epilepsy patients with drug-resistant seizures, surgical resection is the most effective treatment option. The goal of resective surgery is to maximize removal of epileptic foci to attain seizure-freedom while minimizing damage to surrounding brain regions to avoid permanent post-surgical functional loss. Functional MRI enables rapid and non-invasive pre-surgical mapping of language, motor skills and other critical functional brain regions with high spatial resolution. However, excessive head motion presents a major limitation for acquiring high-quality fMRI in pediatric patients with focal brain lesions, who usually have difficulty remaining still for long fMRI scan durations. Unfortunately, current retrospective and prospective approaches cannot adequately compensate for the complex effects of motion in fMRI. As echo planar imaging (EPI) is highly susceptible to local magnetic field variations, motion-induced geometric distortions and blood oxygenation level-dependent (BOLD) contrast changes can lead to potentially significant mislocalization of activation regions, even with accurate head motion tracking. The overarching goal of the research proposed under this application to the NIH is to dramatically improve the quality of fMRI for pre-surgical mapping in pediatric epilepsy patients. We are proposing a solution based on 3D EPI, which is more robust to spin history artifacts and has higher signal-to-noise ratio (SNR) compared to conventional 2D EPI, combined with real-time motion and field compensation. In particular, we will use ultra-fast free induction decay (FID) navigators, which can be embedded in each shot of the 3D EPI acquisition without affecting BOLD contrast or reducing acquisition efficiency. These navigator measurements will be used to produce accurate motion and field estimates that can be used to update the imaging volume and magnetic field in real time. We hypothesize that this improved functional MRI acquisition strategy will produce technically useful activation maps in pediatric epilepsy patients evaluated for a resection surgery at a higher rate than previously thought possible. To achieve these ambitious goals, we will undertake the following specific aims: 1) develop and evaluate a novel technology using FID navigators to measure head motion and magnetic field fluctuations in multi-shot 3D EPI; 2) develop and evaluate prospective motion correction and dynamic shimming utilizing real-time motion and field measurements; 3) apply and evaluate motion and distortion compensation in fMRI of pediatric epilepsy surgery candidates. If successful, our project will facilitate widespread clinical adaptation of fMRI for pre-surgical mapping in epilepsy, and enable high resolution fMRI for research studies in incompliant patient populations.