Callaghan P T, Codd S L
Department of Physics, Massey University, Palmerston North, New Zealand.
Magn Reson Imaging. 1998 Jun-Jul;16(5-6):471-8. doi: 10.1016/s0730-725x(98)00070-8.
The theoretical problem of how to describe apparent image spin density under conditions of restricted diffusion, given any general gradient sequence, is intrinsically complex. Here we demonstrate a simple approach to calculating the signal and the corresponding density in nuclear magnetic resonance (NMR) imaging experiments by means of an impulse-propagator method based on matrix multiplication. The multiplication scheme bears a natural and straightforward relationship to the k-space sampling, while the matrices themselves are calculated from the eigenmodes of the pore diffusion equation. Good agreement is found between theoretical predictions and the results of micro-imaging experiments on water trapped in rectangular pores whose walls are spaced by 100 microns along the read direction.
在任何一般梯度序列的情况下，如何描述受限扩散条件下的表观图像自旋密度这一理论问题本质上都很复杂。在此，我们展示了一种简单的方法，通过基于矩阵乘法的脉冲传播器方法来计算核磁共振（NMR）成像实验中的信号及相应密度。该乘法方案与k空间采样有着自然且直接的关系，而矩阵本身则由孔隙扩散方程的本征模计算得出。在理论预测与对沿读取方向壁间距为100微米的矩形孔隙中所困水的微观成像实验结果之间发现了良好的一致性。
