Asa Carlsson Tedgren1, Hans Bjerke2, Jan-Erik Grindborg3, Per-Otto Hetland2, Antti Kosunen4, Taran Paulsen Hellebust5, Linda Persson3, Petri Sipila4. 1. Swedish Radiation Safety Authority, Stockholm, Sweden; Radiation Physics, Department of Medical and Health Sciences and Center for Medical Image Science and Visualization, Linköping University, Faculty of Health Sciences, Linköping, Sweden. Electronic address: asa.carlsson.tedgren@liu.se. 2. Norwegian Radiation Protection Authority, Österås, Norway. 3. Swedish Radiation Safety Authority, Stockholm, Sweden. 4. STUK-Radiation and Nuclear Safety Authority, Helsinki, Finland. 5. Department of Medical Physics, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway; Department of Physics, University of Oslo, Oslo, Norway.
Abstract
PURPOSE: According to the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism used for dose calculation in brachytherapy treatment planning systems, the absolute level of absorbed dose is determined through coupling with the measurable quantity air-kerma strength or the numerically equal reference air-kerma rate (RAKR). Traceability to established standards is important for accurate dosimetry in laying the ground for reliable comparisons of results and safety in adoption of new treatment protocols. The purpose of this work was to compare the source strength for a high-dose rate (HDR) (192)Ir source as measured using equipment traceable to different standard laboratories in Europe and the United States. METHODS AND MATERIALS: Source strength was determined for one HDR (192)Ir source using four independent systems, all with traceability to different primary or interim standards in the United States and Europe. RESULTS: The measured HDR (192)Ir source strengths varied by 0.8% and differed on average from the vendor value by 0.3%. Measurements with the well chambers were 0.5% ± 0.1% higher than the vendor-provided source strength. Measurements with the Farmer chamber were 0.7% lower than the average well chamber results and 0.2% lower than the vendor-provided source strength. All of these results were less than the reported source calibration uncertainties (k=2) of each measurement system. CONCLUSIONS: In view of the uncertainties in ion chamber calibration factors, the maximum difference in source strength found in this study is small and confirms the consistency between calibration standards in use for HDR (192)Ir brachytherapy.
PURPOSE: According to the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism used for dose calculation in brachytherapy treatment planning systems, the absolute level of absorbed dose is determined through coupling with the measurable quantity air-kerma strength or the numerically equal reference air-kerma rate (RAKR). Traceability to established standards is important for accurate dosimetry in laying the ground for reliable comparisons of results and safety in adoption of new treatment protocols. The purpose of this work was to compare the source strength for a high-dose rate (HDR) (192)Ir source as measured using equipment traceable to different standard laboratories in Europe and the United States. METHODS AND MATERIALS: Source strength was determined for one HDR (192)Ir source using four independent systems, all with traceability to different primary or interim standards in the United States and Europe. RESULTS: The measured HDR (192)Ir source strengths varied by 0.8% and differed on average from the vendor value by 0.3%. Measurements with the well chambers were 0.5% ± 0.1% higher than the vendor-provided source strength. Measurements with the Farmer chamber were 0.7% lower than the average well chamber results and 0.2% lower than the vendor-provided source strength. All of these results were less than the reported source calibration uncertainties (k=2) of each measurement system. CONCLUSIONS: In view of the uncertainties in ion chamber calibration factors, the maximum difference in source strength found in this study is small and confirms the consistency between calibration standards in use for HDR (192)Ir brachytherapy.
Authors: Selma Hurem; Leonardo Martín Martín; Dag Anders Brede; Eystein Skjerve; Rasoul Nourizadeh-Lillabadi; Ole Christian Lind; Terje Christensen; Vidar Berg; Hans-Christian Teien; Brit Salbu; Deborah Helen Oughton; Peter Aleström; Jan Ludvig Lyche Journal: PLoS One Date: 2017-06-19 Impact factor: 3.240