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Gel Dosimetry to Commission a Research Linear Accelerator for Small Field Animal Irradiation Studies

N Ba Sunbul*, I Oraiqat , B Rosen , C Miller , M Matuszak , S Clarke , S Pozzi , J Moran , I El Naqa , Univ of Michigan , Ann Arbor, MI


(Sunday, 7/14/2019)  

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 cm² 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), GAFCHROMIC™ 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 cm² field was measured relative to the reference open field of the Linatron.

Results: The relative output factor of the 2x2 cm² field measured with films and ionization chamber was 0.944±0.019 and 0.940±0.012 respectively. The average field size was measured to be 2.12±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 3.75±0.047 mm. The field size measured with gel was 2.07±0.004 cm with 3.37±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.


Linear Accelerator, Gel Dosimeter, Small Fields


TH- Small Animal RT: Quality Assurance

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