Room: ePoster Forums
Purpose: While small animal irradiation systems meet the imaging and the geometrical requirements of clinical studies, they fall short of capturing megavoltage physical and biological interactions. Therefore, we are repurposing a research linear accelerator (Linatron-9M) and commissioning it with gel dosimetry to optimize its application to small animal irradiation and dosimetry studies.
Methods: The research linear accelerator (Linatron-M9) is a 9 MV linac with static collimated field of 5.08 cm in diameter. Lead collimations were manually placed to shape smaller fields of 2x2 cmÂ² or less. Relative dosimetry measurements, dose profiles, percent depth dose (PDD) curves, beam divergence, and relative output factor were measured using different dosimetry tools, including small volume ionization chamber (A14), GAFCHROMICâ„¢ EBT3 film, and ClearView gel dosimeters. The gel dosimeter was used to provide a full representative 3D dose characterizations of the field. The linac output factor of the 2x2 cmÂ² field was measured relative to the reference open field of the Linatron.
Results: The relative output factor of the 2x2 cmÂ² field measured with films and ionization chamber was 0.944Â±0.019 and 0.940Â±0.012 respectively. The average field size was measured to be 2.12Â±0.012 cm at the point of measurement which was at 34 cm with respect to the collimation at 2 cm depth. The flatness was measured to be 3.62% with a 0.62% symmetry, although their values are limited in this context because the beam does not contain a flattening filter, increasing sensitivity to smoothing and scan resolution. The penumbra was measured to be 3.75Â±0.047 mm. The field size measured with gel was 2.07Â±0.004 cm with 3.37Â±0.011 mm penumbra.
Conclusion: This work provided a commissioning process to measure the beam characteristics of an MV accelerator with detailed dosimetric evaluation for its implementation in megavoltage small animal irradiation studies.