Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.
Magn Reson Med. 2013 Jan;69(1):211-20. doi: 10.1002/mrm.24224. Epub 2012 Feb 29.
Hyperpolarized noble gas ((3)He and (129)Xe) apparent diffusion coefficient (ADC) measurements have shown remarkable sensitivity to microstructural (i.e., alveolar) changes in the lung, particularly emphysema. The ADC of hyperpolarized noble gases depends strongly on the diffusion time (Δ), and (3)He ADC has been shown to be anisotropic for Δ ranging from a few milliseconds down to a few hundred microseconds. In this study, the anisotropic nature of (129)Xe diffusion and its dependence on Δ were investigated both numerically, in a budded cylinder model, and in vivo, in an elastase-instilled rat model of emphysema. Whole lung longitudinal ADC (D(L)) and transverse ADC (D(T)) were measured for Δ = 6, 50, and 100 ms at 73.5 mT, and correlated with measurements of the mean linear intercept (L(m)) obtained from lung histology. A significant increase (P = 0.0021) in D(T) was measured for Δ = 6 ms between the sham (0.0021 ± 0.0005 cm(2)/s) and elastase-instilled (0.005 ± 0.001 cm(2)/s) cohorts, and a strong correlation was measured between D(T) (Δ = 6 ms) and L(m), with a Pearson's correlation coefficient of 0.90. This study confirms that (129)Xe D(T) increases correlate with alveolar space enlargement due to elastase instillation in rats.
超极化稀有气体（氦-3 和氙-129）表观扩散系数（ADC）测量对肺部的微观结构（即肺泡）变化非常敏感，尤其是肺气肿。超极化稀有气体的 ADC 强烈依赖于扩散时间（Δ），并且已经证明氦-3 ADC 在从几毫秒到几百微秒的范围内具有各向异性。在这项研究中，通过数值模拟在分支圆柱模型中以及在体内弹性蛋白酶诱导的肺气肿大鼠模型中，研究了氙-129 的各向异性扩散及其对Δ的依赖性。在 73.5 mT 下，测量了Δ=6、50 和 100 ms 时的全肺纵向 ADC（D(L)）和横向 ADC（D(T)），并与从肺组织学获得的平均线性截距（L(m)）的测量值相关联。在Δ=6 ms 时，与 sham 组（0.0021 ± 0.0005 cm(2)/s）相比，弹性蛋白酶诱导组的 D(T)（0.005 ± 0.001 cm(2)/s）明显增加（P=0.0021），并且在 D(T)（Δ=6 ms）和 L(m)之间测量到强烈的相关性，Pearson 相关系数为 0.90。这项研究证实，氙-129 的 D(T)增加与大鼠弹性蛋白酶诱导的肺泡空间扩大相关。
