A method for z-shim compensated EPI-bold imaging in a single shot

Abstract

Functional MR Imaging (fMRI) is a widely used mechanism to non-invasively evaluate and assess neural activity in the brain, with echo planar imaging (EPI) the most common sequence used in fMRI studies. EPI methods are attractive because they provide functional imaging data of the whole brain at reasonable temporal resolutions. However, EPI is notoriously susceptible to multiple artifacts. This includes Nyquist ghosting caused by mismatched data sampled on positive versus negative readout gradients, and signal loss caused by local magnetic field inhomogeneities. We have recently proposed novel methods to correct for both of these artifacts in EPI. In this paper, we report on the effectiveness of these methods to improve functional MRI studies of deep brain regions including the amygdala and the ventrial medial pre-frontal and orbital-frontal-cortex (vmPFC/vmOFC). Here we review our GESTE method for ghost correction and single-shot z-shim compensation for recovery of signal affected by magnetic susceptibility loss, and compare the results of an emotional stimulus paradigm task both with and with-out these improvements.