Zhu X X, Macdonald P M
Département de Chimie, Université de Montréal, Quebec, Canada.
Solid State Nucl Magn Reson. 1995 May;4(4):217-27. doi: 10.1016/0926-2040(94)00052-e.
An empirical compensation function for the correction of eddy current effects in the Stejskal-Tanner pulsed-gradient spin-echo (PGSE) nuclear magnetic resonance (NMR) experiments has been established. Eddy currents may arise as a result of the application of sharp and strong gradient pulses and may cause severe distortion of the NMR signals. In this method, the length of one gradient pulse is altered to compensate for the eddy current effects. The compensation is considered to be ideal when the position and the phase of the spin-echo maximum obtained from an aqueous solution of poly(ethylene glycol) (PEG) is the same in the presence and absence of a gradient pulse in the PGSE pulse sequence. We first characterized the functional dependence of the length of the required compensation on the three principal variables in the PGSE experiment: the gradient strength, the duration of the gradient pulse, and the interval between the two gradient pulses. Subsequently, we derived a model which successfully describes the general relationship between these variables and the size of the induced eddy current. The parameters extracted from fitting the model to the experimental compensation data may be used to predict the correct compensation for any combination of the three principal variables.
已建立一种经验补偿函数，用于校正斯泰伊卡尔-坦纳脉冲梯度自旋回波（PGSE）核磁共振（NMR）实验中的涡流效应。由于施加尖锐且强的梯度脉冲，可能会产生涡流，这可能会导致NMR信号严重失真。在该方法中，改变一个梯度脉冲的长度以补偿涡流效应。当在PGSE脉冲序列中存在和不存在梯度脉冲时，从聚乙二醇（PEG）水溶液获得的自旋回波最大值的位置和相位相同时，认为这种补偿是理想的。我们首先表征了所需补偿长度对PGSE实验中三个主要变量的函数依赖性：梯度强度、梯度脉冲持续时间以及两个梯度脉冲之间的间隔。随后，我们推导了一个模型，该模型成功描述了这些变量与感应涡流大小之间的一般关系。从将模型拟合到实验补偿数据中提取的参数可用于预测三个主要变量的任何组合的正确补偿。
