期刊
JOURNAL OF MAGNETIC RESONANCE IMAGING
卷 15, 期 1, 页码 87-95出版社
JOHN WILEY & SONS INC
DOI: 10.1002/jmri.10035
关键词
tetrahedral encoded diffusion; EPI diffusion imaging; muscle diffusion anisotropy; muscle diffusion trace; muscle fiber orientation
Purpose: To investigate a tetrahedral diffusion gradient encoding scheme to measure the diffusion tensor in vivo for human calf muscle. Materials and Methods: The theoretical TE which maximizes the signal-to-noise ratio (SNR) of the diffusion images was derived for both the orthogonal and tetrahedral sampling strategies and the SNR advantage verified experimentally. A diffusion echo-planar imaging (EPI) sequence was used to image five volunteers. Gradient cycling and geometric averaging was performed to eliminate cross-terms between the imaging and diffusion gradients. Results: Trace diffusion coefficients in human muscle are spatially invariant and have low intersubject variability (<4%). Images of the off-diagonal terms confirm the anisotropy of muscle, and fiber orientation maps were derived from these off-diagonal images, A noninvariant index of anisotropy, A(ratio) (average value: 1.28), was found to be less susceptible to noise than the invariant index. Conclusion: This technique is robust and can be readily implemented on clinical scanners with EPI capabilities.
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