Implementation of echo-planar imaging on an unmodified spectrometer at 2.1 Tesla for functional imaging

The high speed magnetic resonance imaging technique of Echo-Planar imaging (EPI) has been developing since 1977 using specialized imaging systems. Recent experiments in functional magnetic resonance imaging (FMRI) using EPI on specialized MR systems have generated increased interest in the EPI sequence. Presented here is an implementation of the EPI sequence on a large bore, human scale spectrometer using widely available standard hardware. Existing EPI methods and concepts were amalgamated to obtain images without hardware modifications. Spatial distortion of Echo-Planar images by internal field gradients within the brain were minimized by active shimming on each subject. Nonlinear sampling artifacts caused by nonideal gradient switching were addressed by oversampling the signal and simple extraction of data points corresponding to the ideal sampling pattern. Multislice Echo-Planar images with functional contrast have been obtained at 6 x 3 mm resolution using these methods.