Study of radiation-induced pneumonitis after arc and static irradiation in lungs of rats

The clinical application of the results of the experimental radiotherapy on animals is currently not widely used. The research of radiation injuries after irradiation target in rat lungs using the image-guided platform SmART+ (Precision, North Branford, Conn., USA) is a pilot study for the establishment of an animal model of radiation-induced pulmonary toxicity. Aim: To define the typical doses and target volumes in rat lung to o serve radiation pneumonitis. Material and methods. Four groups of Wistar and Wag rats, distinguishing by age (10–16,5 months) and weight (350-850 g.), were studied. Dosimetric treatment plans were calculated prior to irradiation, using arc or static methods, doses (10–30 Gy), target lung volumes (0,045–1,24 cm3), localization (right or left, top or bottom). Dosimetric planning provides optimal radiation exposure to the target and controls organ at risk doses. Computer tomography (CT) scans were performed for 16 weeks to observe radiation pneumonitis Results. To obtain the rat lung density in Hounsfield units (HU), healthy animals were scanned, CT images were processed, and the mean and standard deviation were calculated. Lung density values of rats (control values) are 519.6 ± 46.2 (HU). Comparison of experimental data on irradiated animals and control values w as carried out. As a result, the relationship of the target volume, the delivered dose and the survival rate of animals after irradiation was established. It was shown that the “mean value of lung density” could be used for quantitative analysis of lung injuries after irradiation. Conclusion. Typical doses and target volumes in rat lungs to observe radiation pneumonitis were obtained. Decreasing aeration of lung tissue was derived at delivered dose 16 Gy and irradiated target volume in lung at least 0.5 cm3 (8%).