Parsons Edward C, Does Mark D, Gore John C
Department of Applied Physics, Yale University, New Haven, CT, USA.
Magn Reson Imaging. 2003 Apr-May;21(3-4):279-85. doi: 10.1016/s0730-725x(03)00155-3.
A variation of the oscillating gradient spin echo method had been developed, which isolates temporal frequencies of the dephasing spectrum. This allows sampling of the diffusion spectrum, the Fourier transform of the velocity correlation function (VCF). It has been shown that restriction and flow alter this function in ways that can be mathematically characterized, yielding quantitative information on restriction geometry and flow parameters. It is demonstrated that in many systems of interest, dispersion of velocity will produce a peak in the VCF spectrum near omega=0, while restricted diffusion will manifest itself in the spectrum at higher frequencies. The method, therefore, may be useful for decoupling their effects on the apparent diffusion coefficient (ADC), as well as in revealing the physics of both phenomena. This method has been implemented in model systems of packed beads, yielding data consistent with theoretical models of restricted diffusion spectra and data from one previous study. The method may have significant application to biology and medicine, as well as the study of transport phenomena in porous media and complex flow.
一种振荡梯度自旋回波方法的变体已经被开发出来，它可以分离去相位谱的时间频率。这使得能够对扩散谱进行采样，扩散谱是速度相关函数（VCF）的傅里叶变换。已经表明，限制和流动以数学上可表征的方式改变这个函数，从而产生关于限制几何形状和流动参数的定量信息。结果表明，在许多感兴趣的系统中，速度色散将在ω = 0附近的VCF谱中产生一个峰值，而受限扩散将在较高频率的谱中表现出来。因此，该方法可能有助于区分它们对表观扩散系数（ADC）的影响，以及揭示这两种现象的物理原理。该方法已在填充珠的模型系统中实现，得到的数据与受限扩散谱的理论模型以及之前一项研究的数据一致。该方法可能在生物学和医学以及多孔介质中的传输现象和复杂流动的研究中有重要应用。
