Balls Gregory T, Frank Lawrence R
Center for Scientific Computation in Imaging, San Diego, California 92103, USA.
Magn Reson Med. 2009 Sep;62(3):771-8. doi: 10.1002/mrm.22033.
Simulations of diffusion in neural tissues have traditionally been limited to analytical solutions, to grid-based solvers, or to small-scale Monte Carlo simulations. None of these approaches has had the capability to simulate realistic complex neural tissues on the scale of even a single voxel of reasonable (i.e., clinical) size. An approach is described that combines a Monte Carlo Brownian dynamics simulator capable of simulating diffusion in arbitrarily complex polygonal geometries with a signal integrator flexible enough to handle a variety of pulse sequences. Taken together, this package provides a complete and general simulation environment for diffusion MRI experiments. The simulator is validated against analytical solutions for unbounded diffusion and diffusion between parallel plates. Further results are shown for aligned fibers, varying packing density and permeability, and for crossing straight fibers.
传统上，神经组织中扩散的模拟仅限于解析解、基于网格的求解器或小规模的蒙特卡罗模拟。这些方法都无法在合理（即临床）大小的单个体素尺度上模拟现实的复杂神经组织。本文描述了一种方法，该方法将能够在任意复杂多边形几何结构中模拟扩散的蒙特卡罗布朗动力学模拟器与足够灵活以处理各种脉冲序列的信号积分器相结合。综上所述，该软件包为扩散磁共振成像实验提供了一个完整且通用的模拟环境。该模拟器针对无界扩散和平行板之间扩散的解析解进行了验证。还展示了对齐纤维、不同堆积密度和渗透率以及交叉直纤维的进一步结果。
