Sørland GH, Aksnes D, Gjerdåker L
Department of Physical Chemistry, Norwegian University of Science and Technology, Trondheim, N-7034, Norway
J Magn Reson. 1999 Apr;137(2):397-401. doi: 10.1006/jmre.1998.1670.
Over the past decade several pulsed field gradient stimulated-echo methods have been presented for diffusion measurements in heterogeneous media. These methods have reduced or eliminated the coupling between the applied magnetic field gradient and a constant internal magnetic field gradient caused by susceptibility changes throughout the sample. For many research purposes the z-storage delay between the second and third pi/2 RF pulse has been included in order to increase the decay of the echo attenuation to an appropriate level and to increase the signal-to-noise ratio by avoiding T2 relaxation of the magnetization in parts of the pulse sequence. For these reasons a stimulated-echo method has been applied instead of a spin-echo method. When studying systems where it is necessary to keep the duration of the pulse sequence at a minimum, and one is not dependent on using z-storage time to increase the echo attenuation or to study diffusion as a function of observation time, a spin-echo method should be chosen. Here we propose a bipolar pulsed field gradient spin-echo method which is well suited to this purpose, and preliminary diffusion measurements are presented as illustration. Copyright 1999 Academic Press.
在过去十年中，已经提出了几种用于在非均匀介质中进行扩散测量的脉冲场梯度刺激回波方法。这些方法减少或消除了外加磁场梯度与由样品中磁化率变化引起的恒定内部磁场梯度之间的耦合。出于许多研究目的，在第二个和第三个π/2射频脉冲之间包含了z存储延迟，以便将回波衰减的衰减增加到适当水平，并通过避免脉冲序列部分中磁化强度的T2弛豫来提高信噪比。由于这些原因，采用了刺激回波方法而不是自旋回波方法。当研究需要将脉冲序列的持续时间保持在最短的系统，并且不依赖于使用z存储时间来增加回波衰减或研究扩散作为观察时间的函数时，应选择自旋回波方法。在此，我们提出一种非常适合此目的的双极脉冲场梯度自旋回波方法，并给出初步扩散测量结果作为示例。版权所有1999年学术出版社。
