Background: Mouse models of radiation-induced lung injury are commonly produced to find novel treatments for the condition. While attempting to irridiate mouse lungs for purposes of creating such a model, noticable declines in health were observed at much earlier time points than recorded for lung pathology. These effects were attributed to off-target effects from imprecise radiation delivery.
Methods: Verification of radiation localization was performed through film dosimetry of the irradiated thorax. Male C57Bl/6 mice were irradiated with a single dose of 20 Gy to the whole thoracic area delivered by an X-Rad cabient irradiator. CT was performed with respitory gating at 2 to 4 week timepoints to which identified abnormal pathology in vivo. Confirmation of CT findings was performed via histology on the stomachs using hematoxylin and eosin staining.
Results: On the CT images, we observed a large, spherecal volume of hypointense signal, caudal to the lungs as easrly as 4 weeks post irradiation. This correlated with a distended stomach caused by constipation and gas build-up within the stomach. Statistical anlysis showed 81% of mice (n=105) died prematurely after irradiation before the desired development of pulmonary fibrosis. Mice sacrificed and disected showed unpassed bolus as contents of the stomach, and histology showed cell metaplasia of the stomach walls.
Conclusion: Imprecise radiation dose delivery to the lungs lead to unexpected pathology of the stomach. Future studies need to consider careful placement of shields or any beam contouring devices to ensure protection of the stomach given its higher radiosensitivity in contrast to the lungs.