Isotropic diffusion‐weighted and spiral‐navigated interleaved EPI for routine imaging of acute stroke

An interleaved echo‐planar imaging (EPI) technique is presented for the rapid acquisition of isotropic diffusion‐weighted images of stroke patients that have excellent lesion‐to‐normal brain contrast, very good spatial resolution, and little sensitivity to susceptibility effects in the base of the brain.

Abstract

An interleaved echo-planar imaging (EPI) technique is presented for the rapid acquisition of isotropic diffusion-weighted images of stroke patients. Sixteen isotropic diffusion-weighted images at three b values are acquired in less than 3 min. A spiral navigator echo is used to measure the constant and linear phase shifts across the head in both the x and y directions which result from motion during the isotropic diffusion- sensitizing gradients. The measured k-space errors are corrected during a gridding reconstruction. The gridding kernel has a constant width in kx and a variable width in ky which eliminates variable data-density ghosts. The resulting isotropic diffusion-weighted images have excellent lesion-to-normal brain contrast, very good spatial resolution, and little sensitivity to susceptibility effects in the base of the brain. Examples of diffusion-weighted images and ADC maps from several stroke patients are shown.