Echo planar imaging of the abdomen.

Echo planar imaging (EPI) is an ultrafast magnetic resonance (MR) imaging method first proposed more than 15 years ago. With EPI, all the information necessary to create an image is obtained very rapidly (typically on the order of 50-150 ms). Special hardware modifications are needed, particularly in the magnetic field gradients and data acquisition systems, to permit such high-speed imaging. In the abdomen, EPI images are insensitive to degradation from breathing or peristaltic motion. The essentially infinite repetition time and lack of motion-induced blurring can improve lesion characterization compared with standard imaging methods. Segmented EPI permits high-resolution T2-weighted images to be acquired within a single breath-hold. Diffusion imaging, which was previously restricted to the brain, can now be done in the abdomen because of the relative insensitivity of EPI images to bulk motion. Diffusion imaging of the kidney has been found to correlate with its functional status. By using EPI readouts, MR angiography can be done more quickly. Further work is needed to improve the spatial resolution and overcome magnetic susceptibility artifacts, particularly with single-shot EPI. Nonetheless, EPI offers considerable potential for improved anatomical and functional imaging of the abdomen.