Purpose:To demonstrate the feasibility of 129 Xe MR in evaluating the pulmonary physiological changes caused by PM 2.5 in animal models. Methods: Six rats were treated with PM 2.5 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 129 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 129 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 2.5 cohort by 129 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 2.5 cohort (P = .021). Conclusions: Hyperpolarized 129 Xe MR could quantify the changes in gas exchange physiology caused by PM 2.5 , indicating that the technique has the potential to be a useful tool for evaluation of pulmonary injury caused by air pollution in the future. K E Y W O R D Sair pollution, gas exchange, hyperpolarized 129 Xe, lung injury, PM 2.5 570 | ZHANG et Al.

Purpose Radiation‐induced lung injury (RILI) is a common side effect in patients with non‐small cell lung cancer (NSCLC) treated with radiotherapy. Minimizing irradiation into highly functional areas of the lung may reduce the occurrence of RILI. The aim of this study is to evaluate the feasibility and utility of hyperpolarized xenon‐129 magnetic resonance imaging (MRI), an imaging tool for evaluation of the pulmonary function, to guide radiotherapy planning. Methods Ten locally advanced NSCLC patients were recruited. Each patient underwent a simulation computed tomography (CT) scan and hyperpolarized xenon‐129 MRI, then received 64 Gyin 32 fractions for radiotherapy. Clinical contours were drawn on CT. Lung regions with good ventilation were contoured based on the MRI. Two intensity‐modulated radiation therapy plans were made for each patient: an anatomic plan (Plan‐A) based on CT alone and a function‐based plan (Plan‐F) based on CT and MRI results. Compared to Plan‐A, Plan‐F was generated with two additional steps: (1) beam angles were carefully chosen to minimize direct radiation entering well‐ventilated areas, and (2) additional optimization criteria were applied to well‐ventilated areas to minimize dose exposure. V20Gy, V10Gy, V5Gy, and the mean dose in the lung were compared between the two plans. Results Plan‐A and Plan‐F were both clinically acceptable and met similar target coverage and organ‐at‐risk constraints (p > 0.05) except for the ventilated lungs. Compared with Plan‐A, V5Gy (Plan‐A: 30.7 ± 11.0%, Plan‐F: 27.2 ± 9.3%), V10Gy (Plan‐A: 22.0 ± 8.6%, Plan‐F: 19.3 ± 7.0%), and V20Gy (Plan‐A: 12.5 ± 5.6%, Plan‐F: 11.0 ± 4.1%) for well‐ventilated lung areas were significantly reduced in Plan‐F (p < 0.05). Conclusion In this pilot study, function‐based radiotherapy planning using hyperpolarized xenon‐129 MRI is demonstrated to be feasible in 10 patients with NSCLC with the potential to reduce radiation exposure in well‐ventilated areas of the lung defined by hyperpolarized xenon‐129 MRI.