Usha Sinha1, Lawrence Yao. 1. Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, California, USA.
Abstract
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. Copyright 2002 Wiley-Liss, Inc.
PURPOSE: To investigate a tetrahedral diffusion gradient encoding scheme to measure the diffusion tensor in vivo for humancalf 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. Copyright 2002 Wiley-Liss, Inc.
Authors: F M Zijta; M Froeling; M P van der Paardt; M M E Lakeman; S Bipat; A D Montauban van Swijndregt; G J Strijkers; A J Nederveen; J Stoker Journal: Eur Radiol Date: 2011-01-01 Impact factor: 5.315
Authors: J F Deux; P Malzy; N Paragios; G Bassez; A Luciani; P Zerbib; F Roudot-Thoraval; A Vignaud; H Kobeiter; A Rahmouni Journal: Eur Radiol Date: 2008-05-08 Impact factor: 5.315