Room: ePoster Forums
Purpose: To investigate the level of sparing provided by fractionated radiation therapy in comparison to single fraction radiation therapy in the mouse brain via irradiation with an X-Rad 320 cabinet irradiator.
Methods: PXi Precision X-Rayâ€™s X-Rad 320 unit was used to conduct mouse irradiations at a dose rate of 2 Gy/min. Mice were anaesthetized with isoflurane, and received radiation to a sub-hemispheric portion of the brain sized 0.5 cm by 0.5 cm. Four fractionation schemes were evaluated: 5 fractions of 20 Gy, 10 fractions of 10 Gy, 5 fractions of 18 Gy, and 10 fractions of 9 Gy. The results of these fractionated irradiations were compared to results from single fraction irradiations with doses ranging from 50 Gy to 100 Gy. The development of radiation necrosis was tracked out to six weeks, with a 7T Bruker MRI using T2 and post-contrast T1 imaging. Histology was obtained after final imaging was performed and scored for lesion severity.
Results: All four fractionation schemes had single fraction equivalent doses less than 50 Gy. Though our single fraction irradiations of 50 Gy did not produce radiation necrosis within 26 weeks, all fractionated regimes led to measurable radiation necrosis on MRI and histology. The two 100 Gy total fractionation schemes had lesion volumes most similar to single fraction irradiations of 90 Gy, while the two 90 Gy total fractionation schemes were most similar to single fraction irradiations of 80 Gy.
Conclusion: Radiation necrosis occurring with these fractionated schemes suggest that the sparing effects of fractionation in our radiation necrosis model are minimal. Fractionation may not be as important a parameter in our murine model compared to parameters such as total dose.