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Initial Experience of the Testing of the IAEA-AAPM Code of Practice for the Dosimetry of Small Static Photon Fields Used in External Beam Radiotherapy

M Huq

M Huq1*, L Wolfgang2 , B Moftah3 , M Arib4 , K Christaki5 , P Francescon6 , F Garcia-Yip7 , R ALFONSO-LAGUARDIA8 , A Ismail9 , R Kinhikar10 , J Larraga-Gutierrez11 , K Raj Mani12 , D van der Merwe13 , O Sauer14 , S Shoeir15 , S Suriyapee16 , A Meghzifene17 , (1) University of Pittsburgh Cancer Institute , Pittsburgh, PA, (2) Medical University Vienna, Vienna, Austria, (3) King Faisal Specialist Hospital and Research Centre, MbC 03, P.O. Box 3354, Saudi Arabia,(4) King Faisal Specialist Hospital and Research Centre, MbC 03, P.O. Box 3354, Saudi Arabia, (5) International Atomic Energy Agency, Vienna, Austria, (6) Ospedale Di Vicenza, Vicenza, (7) Instituto Nacional de Oncologia y Radiobiologia, La Habana, Cuba, (8) Instituto Superior de Ciencias y Tecnologias Aplicadas, INSTEC (9) Protection and Safety Department, Damascus, Syria, (10) Tata Memorial Hospital, Mumbai, Maharashtra, (11) Instituto Nacional de Neurologia y Neurocirugia, Mexico City, Mexico City, (12) Department of Radiation Oncology, United Hospital Ltd, Bangladesh, Bangladesh, (13) University of the Witwatersrand, Johannesburg, South Africa, (14) Univ Wurzburg, Wuerzburg, (15) Radiotherapy Department, Children's Cancer Hospital, Cairo, Egypt, (16) Chulalongkorn Univ, Bangkok,(17) International Atomic Energy Agency, Vienna,


SU-I-GPD-T-495 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The International Atomic Energy Agency (IAEA) and AAPM have jointly developed a new code of practice (CoP), TRS 483, for the dosimetry of small static photon fields. A coordinated research project, consisting of members from twelve countries, was established to test the clinical implementation of the recommendations given in this CoP. This work presents the results of the initial experience of this group in testing of the recommendations of this CoP.

Methods: The task for this group was as follows: i) Performing reference dosimetry in machine-specific reference (msr) fields for 6 MV flattened beam ii) Determination of beam quality index [TPR20,10(10) and %dd(10)X] in msr fields for a 6 MV beam based on measurements in different field sizes, iii) measurements of field output factors for field sizes ranging from 0.5 x0.5 to 10 x 10cm2.

Results: Initial data were available from nine of the twelve countries. Measurements were made in 12 different accelerators from three vendors; a total of 45 detectors were available for all measurements. Reference dosimetry measurements showed consistency among different detectors used for measurements. TPR20,10(10) values ranged between 0.667 and 0.685; %dd (10)X values ranged between 66.4% and 67.6%. The mean value of the differences between calculated TPR20,10(10) and experimentally determined TPR20,10(10) in the 10 x 10 cm² field was -0.05% with a standard deviation of 0.4%; for %dd(10)X, this was -0.5% with a standard deviation of 0.6%. Field output factor measurements were made for 6MV beams. For the majority of the centers, the standard deviations of field output factors were below 1% over a wide range of field sizes and detectors.

Conclusion: The preliminary results of testing the joint IAEA/AAPM CoP has not identified any implementation issue and confirm the consistency of its recommendations for the relative and absolute dosimetry in small static photon fields.

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