• Pippa Storey, Fred J Frigo, R Scott Hinks, Bryan J Mock, Bruce D Collick, Nicole Baker, Jonathan Marmurek, and Simon J Graham.
• Radiology Department, Evanston Northwestern Healthcare, Evanston, Illinois 60201, USA. pstorey@enh.org
• Magn Reson Med. 2007 Mar 1; 57 (3): 614-9.

AbstractPartial k-space sampling is frequently used in single-shot diffusion-weighted echo-planar imaging (DW-EPI) to reduce the TE and thereby improve the SNR. However, it increases the sensitivity of the technique to bulk rotational motion, which introduces a phase gradient across the tissue that shifts the echo in k-space. If the echo is displaced into the high spatial frequencies, conventional homodyne reconstruction fails, causing intensity oscillations across the image. Zero-padding, on the other hand, compromises the image resolution and may cause truncation artifacts. We present an adaptive version of the homodyne algorithm that detects the location of the echo in k-space and adjusts the center and width of the homodyne filters accordingly. The adaptive algorithm produces artifact-free images when the echo is shifted into the high positive k-space range, and reduces to the standard homodyne algorithm in the absence of bulk motion.

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