Fullerton G D, Cameron I L, Ord V A
Radiology. 1984 Apr;151(1):135-8. doi: 10.1148/radiology.151.1.6322223.
The frequency dependence of spin-lattice (T1) relaxation times of protons in tissues and other macromolecular solutions was investigated. This dependence can be principally assigned to reduced mobility of water molecules "hydrated" on the surface of macromolecular structures. The T1 relaxation time of "hydration water" was found to increase linearly with frequency in the range from 5 to 100 MHz (T1 = 1.83 f + 25.0). It is assumed that the remainder of water in the tissue has a relaxation rate that is independent of frequency, as is characteristic of bulk tap water. Variations occur in the fraction of water hydrated or bound from one organ to the next. As the observed relaxation rate is a weighted average of the two rates as described by the fast exchange model, the above empirical relationship can be used to take a tissue T1 relaxation time measured at one frequency and then calculate the tissue T1 relaxation time that would be expected at another frequency. Good agreements were obtained between such calculated tissue T1 values and the T1 values actually measured at the second frequency. Variations between the calculated and measured T1 values in some classes of tissues indicate that there are also less important secondary factors such as lipid content.
研究了组织和其他大分子溶液中质子的自旋晶格（T1）弛豫时间的频率依赖性。这种依赖性主要可归因于在大分子结构表面“水合”的水分子流动性降低。发现“水合水”的T1弛豫时间在5至100 MHz范围内随频率线性增加（T1 = 1.83f + 25.0）。假定组织中其余的水具有与频率无关的弛豫率，这是自来水的特征。从一个器官到另一个器官，水合或结合水的比例会发生变化。由于观察到的弛豫率是快速交换模型所描述的两种速率的加权平均值，因此上述经验关系可用于获取在一个频率下测量的组织T1弛豫时间，然后计算在另一个频率下预期的组织T1弛豫时间。在这些计算出的组织T1值与在第二个频率下实际测量的T1值之间获得了良好的一致性。某些组织类别中计算值与测量值之间的差异表明，还存在不太重要的次要因素，例如脂质含量。
