Dose-response curve of EBT, EBT2, and EBT3 radiochromic films to synchrotron-produced monochromatic x-ray beams

Journal Article · Sat Dec 15 00:00:00 EST 2012 · Medical Physics

DOI:https://doi.org/10.1118/1.4767770· OSTI ID:22097001

Brown, Thomas A. D.; Hogstrom, Kenneth R.; Alvarez, Diane; Matthews, II, Kenneth L.; Ham, Kyungmin; Dugas, Joseph P. ^[1]

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1. Mary Bird Perkins Cancer Center, 4950 Essen Lane, Baton Rouge, Louisiana 70809 and Department of Physics and Astronomy, Louisiana State University and A and M College, 202 Nicholson Hall, Baton Rouge, Louisiana 70803 (United States)

Purpose: This work investigates the dose-response curves of GAFCHROMIC{sup Registered-Sign} EBT, EBT2, and EBT3 radiochromic films using synchrotron-produced monochromatic x-ray beams. EBT2 film is being utilized for dose verification in photoactivated Auger electron therapy at the Louisiana State University Center for Advanced Microstructures and Devices (CAMD) synchrotron facility. Methods: Monochromatic beams of 25, 30, and 35 keV were generated on the tomography beamline at CAMD. Ion chamber depth-dose measurements were used to determine the dose delivered to films irradiated at depths from 0.7 to 8.5 cm in a 10 Multiplication-Sign 10 Multiplication-Sign 10-cm{sup 3} polymethylmethacrylate phantom. AAPM TG-61 protocol was applied to convert measured ionization into dose. Films were digitized using an Epson 1680 Professional flatbed scanner and analyzed using the net optical density (NOD) derived from the red channel. A dose-response curve was obtained at 35 keV for EBT film, and at 25, 30, and 35 keV for EBT2 and EBT3 films. Calibrations of films for 4 MV x-rays were obtained for comparison using a radiotherapy accelerator at Mary Bird Perkins Cancer Center. Results: The sensitivity (NOD per unit dose) of EBT film at 35 keV relative to that for 4-MV x-rays was 0.73 and 0.76 for doses 50 and 100 cGy, respectively. The sensitivity of EBT2 film at 25, 30, and 35 keV relative to that for 4-MV x-rays varied from 1.09-1.07, 1.23-1.17, and 1.27-1.19 for doses 50-200 cGy, respectively. For EBT3 film the relative sensitivity was within 3% of unity for all three monochromatic x-ray beams. Conclusions: EBT and EBT2 film sensitivity showed strong energy dependence over an energy range of 25 keV-4 MV, although this dependence becomes weaker for larger doses. EBT3 film shows weak energy dependence, indicating that it would be a better dosimeter for kV x-ray beams where beam hardening effects can result in large changes in the effective energy.

• OSTI ID: 22097001
• Journal Information: Medical Physics, Vol. 39, Issue 12; Other Information: (c) 2012 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
60 APPLIED LIFE SCIENCES
AUGER ELECTRON SPECTROSCOPY
BRACHYTHERAPY
CALIBRATION
COMPUTERIZED TOMOGRAPHY
DEPTH DOSE DISTRIBUTIONS
DOSEMETERS
DOSIMETRY
ENERGY DEPENDENCE
FILMS
IONIZATION CHAMBERS
KEV RANGE 10-100
MONOCHROMATIC RADIATION
NEOPLASMS
PHANTOMS
RADIATION DOSES
SENSITIVITY
SYNCHROTRON RADIATION
X RADIATION