Effects of pore-size and shape distributions on diffusion pore imaging by nuclear magnetic resonance.
Effects of pore-size and shape distributions on diffusion pore imaging by nuclear magnetic resonance.
复制标题
DOI：
10.1103/physreve.92.022706
复制
发表时间：
2015-08
期刊：
影响因子：
--
通讯作者：
T. Kuder;F. Laun
中科院分区：
文献类型：
--
作者：
T. Kuder;F. Laun
在医学成像和多孔介质研究中，NMR扩散测量被广泛用于研究扩散限制的结构，例如细胞膜。最近，已经提出了几种方法，通过扩散实验明确地确定填充有NMR可见介质的任意闭合孔或单元的形状。第一种方法使用长扩散加权梯度脉冲和短扩散加权梯度脉冲的组合，而其他技术仅采用短梯度脉冲。虽然这些方法的最终目的是确定孔径和形状分布，但到目前为止，重点一直是相同的孔。因此，这项工作的目的是调查这些不同的方法来解决孔径和取向分布的能力。进行模拟，比较采用不同分布的孔径和取向和不同的定时参数的各种孔成像技术。长-窄梯度剖面最有利于研究孔隙分布，因为可以直接获得平均孔隙图像。短梯度方法抑制较大的孔隙或引起相当大的模糊。此外，发生孔隙形状特定的伪影;例如，圆柱体分布的中心部分可能被大大低估。根据实际的孔隙分布，短梯度方法仍然可以产生平均孔隙形状的良好近似值。此外，短梯度方法的应用可以有利于区分孔径分布或强度分布，例如，由于表面弛豫，是主要的。
In medical imaging and porous media research, NMR diffusion measurements are extensively used to investigate the structure of diffusion restrictions such as cell membranes. Recently, several methods have been proposed to unambiguously determine the shape of arbitrary closed pores or cells filled with an NMR-visible medium by diffusion experiments. The first approach uses a combination of a long and a short diffusion-weighting gradient pulse, while the other techniques employ short gradient pulses only. While the eventual aim of these methods is to determine pore-size and shape distributions, the focus has been so far on identical pores. Thus, the aim of this work is to investigate the ability of these different methods to resolve pore-size and orientation distributions. Simulations were performed comparing the various pore imaging techniques employing different distributions of pore size and orientation and varying timing parameters. The long-narrow gradient profile is most advantageous to investigate pore distributions, because average pore images can be directly obtained. The short-gradient methods suppress larger pores or induce a considerable blurring. Moreover, pore-shape-specific artifacts occur; for example, the central part of a distribution of cylinders may be largely underestimated. Depending on the actual pore distribution, short-gradient methods may nonetheless yield good approximations of the average pore shape. Furthermore, the application of short-gradient methods can be advantageous to differentiate whether pore-size distributions or intensity distributions, e.g., due to surface relaxation, are predominant.