Partial k-space reconstruction in single-shot diffusion-weighted echo-planar imaging.
Partial 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.
Storey
Pippa
P
Radiology Department, Evanston Northwestern Healthcare, Evanston, Illinois 60201, USA. pstorey@enh.org
Frigo
Fred J
FJ
Hinks
R Scott
RS
Mock
Bryan J
BJ
Collick
Bruce D
BD
Baker
Nicole
N
Marmurek
Jonathan
J
Graham
Simon J
SJ
D000465:Algorithms; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D009038:Motion; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity