Klein M, Fechete R, Demco D E, Blümich B
Institut für Technische Chemie und Makromolekulare Chemie, Rheinisch-Westfälische Technische Hochschule, Worringerweg 1, Aachen D-52056, Germany.
J Magn Reson. 2003 Oct;164(2):310-20. doi: 10.1016/s1090-7807(03)00237-4.
The simple pulse sequence thetax-tau1-2thetay-tau1+tau2-2thetay-tau2-Hahn echo used to measure the self-diffusion coefficient D under constant-relaxation condition, i.e., for tau1+tau2=const. was investigated in the presence of strongly inhomogeneous static as well as radiofrequency magnetic fields. The encoding of the Hahn-echo amplitude by the pulse flip angle and diffusion was evaluated by taking into account the spatial distribution of the off-resonance field, the strength and orientation of the local field gradients, and the pulse flip angles by a computer simulation program. As input files, this program uses maps of static and radiofrequency fields, and the D coefficient can be evaluated from the time dependence of the Hahn-echo amplitude. The method was applied to a mobile one-sided NMR sensor, NMR-MOUSE with a bar magnet by measuring D for a series of liquids with different viscosities. The method was shown to be particularly useful for measuring D of solvents in elastomers without the need for measurements of the transverse relaxation rates. The self-diffusion coefficient of toluene in a series of crosslinked natural rubber samples was measured and correlated with the crosslink density. Finally, the method was applied to measure the diffusion anisotropy of free water in bovine Achilles tendon.
用于在恒定弛豫条件下（即τ1 + τ2 = 常数）测量自扩散系数D的简单脉冲序列θx - τ1 - 2θy - τ1 + τ2 - 2θy - τ2 - 哈恩回波，在强不均匀静态以及射频磁场存在的情况下进行了研究。通过计算机模拟程序，考虑失谐场的空间分布、局部场梯度的强度和方向以及脉冲翻转角，评估了脉冲翻转角和扩散对哈恩回波幅度的编码。作为输入文件，该程序使用静态和射频场的图谱，并且可以根据哈恩回波幅度的时间依赖性来评估D系数。该方法通过测量一系列不同粘度液体的D，应用于带有条形磁体的便携式单侧核磁共振传感器NMR - MOUSE。结果表明该方法对于测量弹性体中溶剂的D特别有用，无需测量横向弛豫率。测量了一系列交联天然橡胶样品中甲苯的自扩散系数，并将其与交联密度相关联。最后，该方法应用于测量牛跟腱中自由水的扩散各向异性。
