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A Study of Dose Response Characteristic for Gafchromic EBT2 Film

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W Chen

W Chen1*, X Di1, S Wang2, B Wang1, X Bai1, J Yang1, B Guo3, K Huang3, (1) Zhejiang Cancer Hospiatl, Hangzhou, Zhejiang, (2) Tsinghua University, Beijing, Beijing, (3) University of Michigan, Ann Arbor, MI

SU-E-T-39 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The self-developing Gafchromic EBT2 film (International Specialty Products, Wayne, NJ) is a radiochromic film widely used for relative photon dosimetry. Different from the traditional radiochromic film, EBT2 is colored, hence the dose response sensitivity of EBT2 film will be different when the film is scanned by different light source. The dosimetry software FILMQA provides the function to separate 48 bits color image into three 16 bits gray maps corresponding red, green and blue scanner light respectively. We focused on studying the dose response characteristic of EBT2 film when it was scanned by red, green and blue light source.

Methods: The EBT2 film was placed in solid water phantom, radiated with 6MV photon beam. Delivered dose to the film spanned from 0 to 280 cGy. The film was scanned with flatbed color scanner and the scanned images were separated into red, green and blue channels respectively. The characteristic of image's dose response was analyzed.

Results: The dose response sensitivity of the EBT2 film is different when it was scanned by different light source. The sequence of dose response sensitivity is 109.8, 88.1 and 29.9 (Δpixel value/ΔcGy)corresponding to scanner light source in red, green and blue. Cubic polynomial fitting method can satisfy the requirement of dose response curve.

Conclusion: Dose response sensitivity of EBT2 films descended with the increased of absorption dose. The dose response ability appears different when it is scanned in different light source.

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