Journal of Medical Physics and Applied Sciences

An Investigation on the Dependence of EBT-3 Gafchromic Film on Energy, Dose, and Post-Exposure Scanning Time

Background: The Gafchromic EBT-3 film is widely used in radiation oncology to measure dose distribution and absolute doses for various energies. EBT-3 films are exposed to radiation over a wide energy range and doses to provide a complete picture of energy and dose dependency. Additionally, we also examined the evolution of optical density as a function of time after irradiation.

Materials and methods: The study used ⁶⁰Co gamma (1.17-1.33) MeV and megavoltage X-rays (6,10 and 15 MV) to measure the film’s response to energy. The Gafchromic EBT-3 film’s response to each of the above energies was meas ured over the dose range of (0.1-10 Gy). The optical densities of irradiated films were read 24,48 and 72 h after irradiation to evaluate the fluctuation of optical density with post-exposure scanning time. The study used an Epson Expression12000 XL flatbed scanner and Image-J software to assess the optical densities. Each film strip was placed on the scanner bed with care in the same orientation at the same location.

Results: When compared to ⁶⁰Co, the optical density of the EBT-3 film was noticeably different for the three energies 6, 10 and 15 MV. For 15 MV higher differences are seen at lower doses and gradually decrease with the increase of doses, with 18.2% at 10 cG y and 6.5% at 1000 cGy. For the dose above 100 cGy, no statistical difference was observed between 6 and 15 MV beams. We observed no significant changes of optical density due to various post-irradiation times. But compared to higher doses very minor changes are noticed in lower doses, which is not statistically significant.

Conclusion: According to the findings of our study indicate that Gafchromic EBT-3 film is a reliable dosimeter with insignificant energy-independent responses across a wide range of beam energies and modalities used in radiation oncology.

Author(s): Jibon Sharma*and Banashree Kalita

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