Sukstanskii A L, Ackerman J J H, Yablonskiy D A
Department of Radiology, Washington University, St. Louis, Missouri 63110, USA.
Magn Reson Med. 2003 Oct;50(4):735-42. doi: 10.1002/mrm.10586.
The spatial distribution of the transverse nuclear spin magnetization, appearing in a single compartment with impermeable boundaries in a Stejskal-Tanner gradient pulse MR experiment, is analyzed in detail. At short diffusion times the presence of diffusion-restrictive barriers (membranes) reduces effective diffusivity near the membranes and leads to an inhomogeneous spin magnetization distribution (the edge-enhancement effect). In this case, the signal reveals a quasi-two-compartment behavior and can be empirically modeled remarkably well by a biexponential function. The current results provide a framework for interpreting experimental MR data on various phenomena, including water diffusion in giant axons, metabolite diffusion in the brain, and hyperpolarized gas diffusion in lung airways.
详细分析了在Stejskal-Tanner梯度脉冲磁共振实验中，出现在具有不可渗透边界的单个隔室中的横向核自旋磁化强度的空间分布。在短扩散时间内，扩散限制屏障（膜）的存在会降低膜附近的有效扩散率，并导致自旋磁化强度分布不均匀（边缘增强效应）。在这种情况下，信号呈现出准双室行为，并且可以通过双指数函数很好地进行经验建模。当前结果为解释关于各种现象的实验磁共振数据提供了一个框架，这些现象包括巨轴突中的水扩散、大脑中的代谢物扩散以及肺气道中的超极化气体扩散。
