Temporal diffusion spectroscopy: Theory and implementation in restricted systems using oscillating gradients
Temporal diffusion spectroscopy: Theory and implementation in restricted systems using oscillating gradients
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DOI：
10.1002/mrm.20732
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发表时间：
2006-01-01
影响因子：
3.3
通讯作者：
Gore, JC
中科院分区：
文献类型：
--
作者：
Parsons, EC;Does, MD;Gore, JC
回顾了时间扩散谱理论。与在空间域测量自旋位移谱的Q空间谱不同，它考虑了时间域中速度关联函数的谱密度。结果表明，在这一领域中的铸造扩散有助于测量微观几何形状，并由于弥散流动和限制扩散而将扩散信号分解成分量。提出并实现了扩散光谱的振荡梯度(OG)方法。用这种方法从模型系统中提取了微观孔尺寸、表面体积比(SNS)和扩散路径弯曲度。讨论了当空间域实验失败时，这种类型的实验可能允许表征孔几何形状的情况。OGS可以与成像序列相结合，以绘制扩散和流动的复杂模式。此外，复杂生物系统中的标量表观扩散系数(ADC)测量可能微妙地依赖于特定的脉冲序列参数。因此，使用不同频谱的梯度脉冲进行标量ADC测量可能会给出不同的结果。相反，可以利用运动敏化梯度脉冲的频率相关性来推断ADC变化的起源。
The theory of temporal diffusion spectra is reviewed. In contrast to q-space spectroscopy, which measures the displacement spectrum of spins in a spatial domain, the spectral density of the velocity correlation function (VCF) in the temporal domain is considered. It is demonstrated that casting diffusion in this domain may facilitate measurements of microscopic geometry and the decomposition of the diffusion signal into components due to disperse flow and restricted diffusion. An oscillating gradient (OG) method of diffusion spectroscopy was developed and implemented. Microscopic pore sizes, surf ace-to-volume ratios (SNs), and diffusion path tortuosities were extracted from model systems using this method. Cases are discussed in which this type of experiment may allow the characterization of pore geometry when spatial domain experiments fail. OGs may be combined with imaging sequences to map complex patterns of diffusion and flow. Moreover, scalar apparent diffusion coefficient (ADC) measurements in complex biological systems may be subtly dependent on specific pulse sequence parameters. Thus, scalar ADC measurements using gradient pulses with different frequency spectra may give different results. Conversely, the frequency dependence of motion-sensitizing gradient pulses may be exploited to deduce the origin of ADC changes.