Comparative Study of Novel Versus Conventional Scanning Modalities for Radiochromic Film Dosimetry
B Rosen1*, C Soares2, R Minniti2, L DeWerd1, (1) University of Wisconsin-Madison, Madison, WI, (2) National Institute of Standards and Technology, Gaithersburg, MDWE-E-141-3 Wednesday 2:00PM - 3:50PM Room: 141
Purpose: To compare the dose response of GAFCHROMIC(R) EBT3 film as measured using conventional document scanner readout to that of a custom-built laser densitometry system (LDS), and to assess the intrinsic film orientation dependence to coherent light in order to optimize its use in radiation dosimetry.
Methods: 108 1x1cm² pieces of EBT3 film were cut from a single sheet and read on an Epson 10000XL document scanner (DOC) and on a point-to-point LDS equipped with a 635nm diode laser and spectrally matched photodetector. Pixel values were converted to optical density (OD) using calibrated neutral-density filters. Packets of six films were sealed and mounted at 5cm depth in water perpendicular to a ⁶⁰Co beam, then exposed to one of 16 dose levels between 30 mGy and 10 Gy. Films were then re-read to obtain net change in OD (NOD) using both readout modalities. The DOC readouts were repeated for two orthogonal film orientations, and for LDS, with the laser oriented at 9 evenly spaced angles between 0 and 180 degrees.
Results: Four to five-fold increases in NOD measured with LDS as compared to DOC were found over the full dose range. A sinusoidal relationship of NOD versus angle was found at each dose level, and its amplitude increased with dose. The ability for LDS over DOC to distinguish between films exposed to low doses was statistically significant, especially when optimized for scanning angle.
Conclusion: This work indicates the potential of radiochromic film, in conjunction with novel scanning methods, to form a dosimetric standard by extending and improving the usable range as a result of increased NOD, primarily through exploitation of the emulsion polarization to coherent light. Future work will attempt to quantify energy dependence in order to form a fully characterized dosimetry system that can be traced to primary dose standards.
Funding Support, Disclosures, and Conflict of Interest: Acknowledgement: The authors wish to thank Dr. David Lewis of Ashland, Inc. of Wayne, NJ for making the EBT3 film available to us for these measurements.