Quantitative evaluation of lung injury caused by PM using hyperpolarized gas magnetic resonance.

Purpose: To demonstrate the feasibility of Xe MR in evaluating the pulmonary physiological changes caused by PM in animal models.

Methods: Six rats were treated with PM solution (16.2 mg/kg) by intratracheal instillation twice a week for 4 weeks, and another six rats treated with normal saline served as the control cohort. Pulmonary function tests, hyperpolarized Xe multi-b diffusion-weighted imaging, and chemical shift saturation recovery MR spectroscopy were performed on all rats, and the pulmonary structure and functional parameters were obtained from hyperpolarized Xe MR data. Additionally, histological analysis was performed on all rats to evaluate alveolar septal thickness. Statistical analysis of all the obtained parameters was performed using unpaired 2-tailed t tests.

Results: Compared with the control group, the measured exchange time constant increased from 11.74 ± 2.39 to 14.00 ± 2.84 ms (P < .05), and the septal wall thickness increased from 6.17 ± 0.48 to 6.74 ± 0.52 μm (P < .05) in the PM cohort by Xe MR spectroscopy, which correlated well with that obtained using quantitative histology (increased from 5.52 ± 0.32 to 6.20 ± 0.36 μm). Additionally, the mean TP/GAS ratio increased from 0.828 ± 0.115 to 1.019 ± 0.140 in the PM cohort (P = .021).

Conclusions: Hyperpolarized Xe MR could quantify the changes in gas exchange physiology caused by PM , indicating that the technique has the potential to be a useful tool for evaluation of pulmonary injury caused by air pollution in the future.