High‐resolution DTI of a localized volume using 3D single‐shot diffusion‐weighted STimulated echo‐planar imaging (3D ss‐DWSTEPI)

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Abstract
Diffusion tensor MRI (DTI) using conventional single‐shot (SS) 2D diffusion‐weighted (DW)‐EPI is subject to severe susceptibility artifacts. Multishot DW imaging (DWI) techniques can reduce these distortions, but they generally suffer from artifacts caused by motion‐induced phase errors. Parallel imaging can also reduce the distortions if the sensitivity profiles of the receiver coils allow a sufficiently high reduction factor for the desired field of view (FOV). A novel 3D DTI technique, termed 3D single‐shot STimulated EPI (3D ss‐STEPI), was developed to acquire high‐resolution DW images of a localized region. The new technique completes k‐space acquisition of a limited 3D volume after a single diffusion preparation. Because the DW magnetization is stored in the longitudinal direction until readout, it undergoes T1 rather than T2 decay. Inner volume imaging (IVI) is used to limit the imaging volume. This reduces the time required for EPI readout of each complete kx‐ky plane, and hence reduces T decay during the readout and T1 decay between the readout of each kz. 3D ss‐STEPI images appear to be free of severe susceptibility and motion artifacts. 3D ss‐STEPI allows high‐resolution DTI of limited volumes of interest, such as localized brain regions, cervical spinal cord, optic nerve, and other extracranial organs. Magn Reson Med, 2006.