(a) High resolution computed tomography (CT) as a non-invasive tool for qualitative and quantitative longitudinal monitoring of pulmonary fibrosis progression in mice. Representative CT scans showing progression of pulmonary fibrosis in mice after 20 Gy whole thorax irradiation (RT), and treatment with imatinib treatment starting 3 days and 2 weeks after radiation (RT). Fibrosis is characterized by diffuse bilateral areas of "ground-glass" attenuation and intralobular reticular opacities. (b) Quantitative lung density values derived from CT scans. The same 5 randomly chosen mice in each treatment group were examined in a longitudinal study by CT every 2 weeks. 8 regions of interest (ROI) were randomly selected in the lungs and the lung density (in Hounsfield Units (HU)) was determined for each ROI. Mean ± SE are presented. * P < 0.01 vs. the RT only group; # P < 0.01 vs. the control group.