Assessment of Lung Microvasculature Alterations in Pulmonary Fibrosis With Hyperpolarized Xenon Magnetic Resonance

To evaluate the feasibility of measuring gas exchange between the alveolar-capillary membrane and red blood cells (RBCs) using hyperpolarized ¹²⁹Xe magnetic resonance, and to assess its potential for detecting disease-related changes in an animal model.

Experiments were performed on eight rats with bleomycin-induced pulmonary fibrosis and eight healthy controls. RBCs chemical shift saturation recovery (rCSSR) and equivalent chemical shift saturation recovery (eCSSR) sequences were developed to estimate the gas exchange time constants from alveoli to RBCs (T_G-R) and from membrane to RBCs (T_M-R). Group comparisons were performed, and correlations between rCSSR-derived parameters and pulmonary function tests (PFTs) and quantitative histology were also assessed. Statistical significance was defined as p < 0.05.

T_M-R and T_G-R measured with rCSSR (denoted as T_M-R-R and T_G-R-R, respectively) were higher in the fibrosis group (8.74 ± 1.26 and 17.80 ± 3.08 ms, respectively) compared to controls (7.02 ± 0.58 and 13.89 ± 1.58 ms; p < 0.01). For the T_M-R and T_G-R derived from eCSSR (denoted as T_M-R-E and T_G-R-E, respectively), only T_G-R-E showed a significant difference. Additionally, T_M-R-R demonstrated strong correlations with forced vital capacity, quasi-static compliance from PFTs, and alveolar septal thickness measured by histology.

We proposed a ¹²⁹Xe MR-based approach for quantifying gas exchange from the alveolar-capillary membrane to RBCs. This technique shows promise as a sensitive, non-invasive tool for detecting pulmonary gas exchange impairment.