Measurement of ¹²⁹Xe gas apparent diffusion coefficient anisotropy in an elastase‐instilled rat model of emphysema

Abstract

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.

Commentary on “The influence of lung airways branching structure and diffusion time on measurements and models of short-range 3He gas MR diffusion”

“…This fundamental property of gas diffusion in lung acinar airways was confirmed by experimental MRI measurements in humans (2,4,6), canines (15), mice (8,9) and rats (10,16) using hyperpolarized 3 He gas. It was also recently confirmed in humans (17) and rats (18) using hyperpolarized 129 Xe gas.…”

Probing lung microstructure with hyperpolarized noble gas diffusion MRI: theoretical models and experimental results

“…The first 129 Xe applications of in vivo lung morphometry technique have been demonstrated by Ruppert et al (see example in Fig. ) and Ouriadov et al in humans, and Boudreau et al , and Hegarty et al in rats.…”

Magnetic resonance imaging with hyperpolarized agents: methods and applications

“…These studies have served a useful role in optimizing 129 Xe DWI [216, 217] via comparison with the more mature 3 He DWI. Similar studies have explored the anisotropy and dependence on delay time of dimensional measures derived from DWI for both 3 He [218] and 129 Xe [219]. …”