Thesis: Stereotactic Body Radiation Therapy (SBRT) is a therapeutic alternative for patients with bronchial cancer at high surgical risk. It is a high- precision technique, allowing the irradiation of very small volumes. However, some patients develop pulmonary fibrosis. Our preclinical SBRT model allows to irradiate about 4% of the mouse lung and has shown a macrophage infiltrate. The objective was to characterize the different subpopulations of pulmonary macrophages, and their presumed role in the development of focal radiation-induced lung lesions. Imaging, histology, cytometry, and single cell RNAseq techniques allowed us to observe the absence of impact of macrophage recruitment on the severity of the lesions as well as the presence of proliferating alveolar macrophages after irradiation. Their metabolism may switch from energetic use of fatty acids to cholesterol biosynthesis.