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Cross-Comparison of Three Radiochromic Film Imaging Systems

L Schreiner

KM Alexander1, T Olding1,2,3, LJ Schreiner1,2,3*, (1) Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, Ontario. (2) Medical Physics Department, Cancer Centre of Southeastern Ontario at Kingston General Hospital, Kingston, Ontario. (3) Department of Oncology, Queen's University, Kingston, Ontario.


SU-I-GPD-T-543 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Radiochromic film is widely recognized as an easy-to-use, high resolution dosimeter, but accurate and reliable film readout remains an on-going challenge. In this work, we compare three different film imaging systems: a flatbed scanner, and two systems that were custom built in-house. We examine key optical properties and imaging parameters to determine the strengths and weaknesses of each imaging system.

Methods: Gafchromic EBT3 radiochromic film was used for all irradiations, and the three imaging systems consisted of a commercially available Epson 10000XL flatbed scanner, and two in-house built systems that feature a digital camera mounted above either a diffuse red light field (film placed on light field surface), or a red LED point source magnified by two condenser lenses (film placed on transparent stage above lenses). The limiting spatial resolution, light field uniformity and stability, dynamic range, effects of masking the light field to the film (to reduce stray light), and dependence on film orientation for each system were examined. Since scattered light is a significant cause of discrepancy in film imaging, the scatter contribution for optical density measurements was characterized for each imaging system using film irradiations of equal dose but various field sizes.

Results: Our in-house imaging systems produce up to a 2.5% difference in optical density for equal dose film irradiations between 10x10 cm² and 3x3 cm². While the Epson scanner shows slightly less discrepancy for different field size irradiations, it suffers from a number of issues, including substantial dependence on film orientation, whereas the in-house systems do not.

Conclusion: Three different film imaging systems have been characterized and compared, showing the benefits/pitfalls of each. While none of the imaging systems are perfect, the source of error in each system can be minimized through a working knowledge of each system’s strengths and weaknesses.

Funding Support, Disclosures, and Conflict of Interest: We acknowledge and appreciate support from Modus Medical Devices Inc. and the CIHR (Canadian Institutes for Health Research)

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