Self-diffusion anisotropy of water in sheep Achilles tendon
Self-diffusion anisotropy of water in sheep Achilles tendon
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DOI：
10.1002/nbm.995
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发表时间：
2005-12-01
影响因子：
2.9
通讯作者：
Navon, G
中科院分区：
文献类型：
--
作者：
Fechete, R;Demco, DE;Navon, G
本文测定了绵羊跟腱孔内自由水扩散张量的主值。为此，使用射频倾斜线圈和脉冲场梯度激励回波（PFGSE）NMR测量自扩散系数的方位角依赖性。将PFGSE与使用Carr-Purcell-Meiboom-Gill脉冲序列的Hahn回波的多次采集相结合，减少了测量时间。扩散测量揭示了两个扩散过程，其特征在于快速和缓慢的有效扩散系数。描述受激回波幅度的模型，由水扩散和磁化转移编码。用于评估快速扩散系数。快速扩散过程表征了胶原纤维周围孔隙中的水分子。表征快速过程的扩散系数显示出明确的各向异性。扩散张量的主值的确定假设细长孔平行于肌腱原纤维取向，因此孔的取向分布函数遵循胶原原纤维的取向分布函数。孔隙的平均纵横比估计从水扩散张量的主要值，是合适的定量表征肌腱形态的变化，由于愈合或老化。在这项调查中的方法也可以应用到测量的扩散各向异性使用非原位NMR传感器。版权所有（c）2005年约翰威利父子有限公司。
The principal values of the diffusion tensor of free water in the pores of sheep Achilles tendon were determined. For this purpose, the azimuthally angular dependence of the self-diffusion coefficient was measured using a radiofrequency tilt coil and pulsed-field-gradient stimulated-echo (PFGSE) NMR. Combining the PFGSE with multiple acquisitions of Hahn echoes using the Carr-Purcell-Meiboom-Gill pulse sequence reduced the measuring time. The diffusion measurements revealed two diffusion process characterized by a fast and a slow effective diffusion coefficient. A model which describes the stimulated-echo amplitude, encoded by the water diffusion and magnetization transfer. was used for evaluation of the fast diffusion coefficients. The fast diffusion process characterizes the water molecules in pores surrounding the collagen fibrils. The diffusion coefficients characterizing the fast process show a well-defined anisotropy. The principal values of the diffusion tensors were determined assuming the elongated pores to be oriented parallel to the tendon fibrils and thus the orientation distribution function of the pores followed that of the collagen fibrils. The average aspect ratio of pores was estimated from the principal values of the water diffusion tensor and is suitable to characterize quantitatively the changes in tendon morphology due to healing or aging. The methods in this investigation can also be applied to measurements of the diffusion anisotropy using ex situ NMR sensors. Copyright (c) 2005 John Wiley & Sons, Ltd.