Scanning orientation and polarization effects for XRQA radiochromic film |
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| Authors: | Hani Alnawaf Martin J Butson Tsang Cheung Peter KN Yu |
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| Institution: | 1. City University of Hong Kong, Dept. of Physics and Materials Science, Kowloon Tong, Hong Kong;2. Illawarra Cancer Care Centre, Department of Medical Physics, Crown St., Wollongong, NSW 2500, Australia;3. Centre for Medical Radiation Physics, University of Wollongong, Northfields Ave., Gwynneville, NSW, Australia;1. Dipartimento di Scienze Ambientali, Seconda Università di Napoli, Via A Vivaldi 43, Caserta, Italy;2. Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Via Cinthia, Napoli, Italy;3. Istituto Nazionale di Fisica Nucleare—Sezione di Napoli, Napoli, Italy;1. BMW Group Research and Technology, München, Germany;2. Technische Universität München, Lehrstuhl für Mensch Maschine Kommunikation, München, Germany;3. Technische Universität München, Lehrstuhl für Betriebssysteme, Garching bei München, Germany;1. Department of Mathematics and Statistics, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus;2. Department of Mathematics, South Kensington Campus, Imperial College London, SW7 2BZ England, UK;3. Institute for the Information Transmission Problems, Russian Academy of Sciences, 19 Bolshoi Karetnyi, Moscow, 127994, Russia;1. Department of Medical Imaging and Radiological Sciences, I-Shou University, Kaohsiung, Taiwan;2. Department of Radiation Oncology, Chi Mei Medical Center, Liouying, Tainan, Taiwan;3. Medical Physics and Informatics Laboratory, Department of Electronics Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan;4. Department of Radiation Oncology, E-Da Hospital, Kaohsiung, Taiwan;5. Department of Radiation Oncology, Sinlau Christian Hospital, Tainan, Taiwan |
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| Abstract: | Gafchromic XRQA radiochromic film, is an effective tool for quality assurance and dose assessment in kilovoltage radiotherapy and diagnostic applications. Like other Gafchromic film products, XRQA film exhibits a variation in dose to reflected optical density response with angle of rotation when analysed with a light source that is partially or fully polarised such as a desktop scanner. Although warnings are not given on manufacturers specifications, this can affect dosimetry accuracy and we recommend that it is essential to scan all XRQA films in the same orientation. The effect is not as pronounced as EBT Gafchromic film. The magnitude of this variation has been measured and shown to be up to 16 ± 2% (1SD) using a fully linear polarised light source was seen with a 90° angle rotation. This would be the maximum variation seen on a desktop scanner with a fully polarised light source. For our standard desktop scanner (Epson v700) a mean variation of 2 ± 1% from 0 cGy to 20 cGy applied dose was measured as compared to 8 ± 2% for EBT Gafchromic. We recommend that to decrease uncertainty in dose measurement, accurate alignment of the calibration films to experimental films be performed on a regular basis. This is especially important if your desktop scanner has a high degree of polarization of its light source. |
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