Diffusion imaging in humans at 7T using readout-segmented EPI and GRAPPA.

Anatomical MRI studies at 7T have demonstrated the ability to provide high-quality images of human tissue in vivo. However, diffusion-weighted imaging at 7T is limited by the increased level of artifact associated with standard, single-shot, echo-planar imaging, even when parallel imaging techniques such as generalized autocalibrating partially parallel acquisitions (GRAPPA) are used to reduce the effective echo spacing. Readout-segmented echo-planar imaging in conjunction with parallel imaging has the potential to reduce these artifacts by allowing a further reduction in effective echo spacing during the echo-planar imaging readout. This study demonstrates that this approach does indeed provide a substantial improvement in image quality by reducing image blurring and susceptibility-based distortions, as well as by allowing the acquisition of diffusion-weighted images with a high spatial resolution. A preliminary application of the technique to high-resolution diffusion tensor imaging provided a high level of neuroanatomical detail, which should prove valuable in a wide range of applications.