Cyberknife Relative Output Factor measurements using fiber-coupled luminescence, MOSFETS and RADPOS dosimetry system

N. Ploquin, Gustavo Adolfo Vladimir Kertzscher Schwencke, E. Vandervoort, J. E. Cygler, Claus Erik Andersen, P. Francescon

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    Abstract

    Novel dosimetry systems based on Al2O3:C radioluminescence (RL) and a 4D dosimetry system (RADPOS) from Best Medical Canada were used to measure the relative output factor (ROF) on Cyberknife. Measurements were performed in a solid water phantom at the depth of 1.5 cm and SSD = 78.5 cm for cones from 5 to 60 mm. ROFs were also measured using a mobileMOSFET system (Best Medical Canada) and EBT1 and EBT2 GAFCHROMIC® (ISP, Ashland) radiochromic films. For cone sizes 12.5–60 mm all detector results were in agreement within the measurement uncertainty. The microMOSFET/RADPOS measurements (published corrections applied) yielded ROFs of 0.650 ± 1.9%, 0.811 ± 0.9% and 0.843 ± 1.7% for the 5, 7.5 and 10 mm cones, respectively, and were in excellent agreement with radiochromic film values (averaged for EBT1 and EBT2) of 0.645 ± 1.4%, 0.806 ± 1.1% and 0.859 ± 1.1%. Monte‐Carlo calculated correction factors were applied to the RL readings to correct for excessive scatter due to the relatively high effective atomic number of Al2O3 (Z=10.2) compared to water for the 5, 7.5 and 10 mm cones. When these corrections are applied to our RL detector measurements, we obtain ROFs of 0.656 ± 0.3% and 0.815 ± 0.3% and 0.865 ± 0.3% for 5, 7.5 and 10 mm cones. Our study shows that the microMOSFET/RADPOS and optical fiber‐coupled RL dosimetry system are well suited for Cyberknife cone output factors measurements over the entire range of field sizes, provided that appropriate correction factors are applied for the smallest cone sizes (5, 7.5 and 10 mm).

    © 2012 American Association of Physicists in Medicine
    Original languageEnglish
    JournalMedical Physics
    Volume39
    Issue number7
    Pages (from-to)4643-4643
    ISSN0094-2405
    DOIs
    Publication statusPublished - 2012
    Event54th Annual Meeting and Exhibition of the American Association of Physicists in Medicine (AAPM) - Charlotte, NC, United States
    Duration: 29 Jul 20122 Aug 2012
    Conference number: 54

    Conference

    Conference54th Annual Meeting and Exhibition of the American Association of Physicists in Medicine (AAPM)
    Number54
    CountryUnited States
    CityCharlotte, NC
    Period29/07/201202/08/2012

    Bibliographical note

    54th Annual Meeting of the Canadian Organization of Medical Physicists and the Canadian College of Physicists in Medine

    Cite this

    Ploquin, N., Kertzscher Schwencke, G. A. V., Vandervoort, E., Cygler, J. E., Andersen, C. E., & Francescon, P. (2012). Cyberknife Relative Output Factor measurements using fiber-coupled luminescence, MOSFETS and RADPOS dosimetry system. Medical Physics, 39(7), 4643-4643. https://doi.org/10.1118/1.4740202