Pavel Kazantsev1, Wolfgang Lechner2,3, Eduard Gershkevitsh4, Catharine H Clark5,6, Daniel Venencia7, Jacob Van Dyk8, Paulina Wesolowska1, Victor Hernandez9, Nuria Jornet10, Milan Tomsej11, Tomislav Bokulic1, Joanna Izewska1. 1. International Atomic Energy Agency, Vienna, Austria. 2. Department of Radiation Oncology, Division of Medical Physics, Medical University of Vienna, Vienna, Austria. 3. Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria. 4. North Estonia Medical Centre, Tallinn, Estonia. 5. Department of Medical Physics, Royal Surrey County Hospital, Guildford, UK. 6. Metrology for Medical Physics (MEMPHYS), National Physical Laboratory, Teddington, UK. 7. Instituto Privado de Radioterapia, Cordoba, Argentina. 8. Department of Oncology and Medical Biophysics, Western University, London, Canada. 9. Department of Medical Physics, Hospital Sant Joan de Reus, IISPV, Tarragona, Spain. 10. Servei de Radiofisica i Radioproteccio, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. 11. CHU Charleroi, Hopital Andre Vesale, Montigny-le-Tilleul, Belgium.
Abstract
Background: The IAEA has developed and tested an on-site, end-to-end IMRT/VMAT dosimetry audit methodology for head and neck cases using an anthropomorphic phantom. The audit methodology is described, and the results of the international pilot testing are presented.Material and methods: The audit utilizes a specially designed, commercially available anthropomorphic phantom capable of accommodating a small volume ion chamber (IC) in four locations (three in planning target volumes (PTVs) and one in an organ at risk (OAR)) and a Gafchromic film in a coronal plane for the absorbed dose to water and two-dimensional dose distribution measurements, respectively. The audit consists of a pre-visit and on-site phases. The pre-visit phase is carried out remotely and includes a treatment planning task and a set of computational exercises. The on-site phase aims at comparing the treatment planning system (TPS) calculations with measurements in the anthropomorphic phantom following an end-to-end approach. Two main aspects were tested in the pilot study: feasibility of the planning constraints and the accuracy of IC and film results in comparison with TPS calculations. Treatment plan quality was scored from 0 to 100. Results: Forty-two treatment plans were submitted by 14 institutions from 10 countries, with 79% of them having a plan quality score over 90. Seventeen sets of IC measurement results were collected, and the average measured to calculated dose ratio was 0.988 ± 0.016 for PTVs and 1.020 ± 0.029 for OAR. For 13 film measurement results, the average gamma passing rate was 94.1% using criteria of 3%/3 mm, 20% threshold and global gamma.Conclusions: The audit methodology was proved to be feasible and ready to be adopted by national dosimetry audit networks for local implementation.
Background: The IAEA has developed and tested an on-site, end-to-end IMRT/VMAT dosimetry audit methodology for head and neck cases using an anthropomorphic phantom. The audit methodology is described, and the results of the international pilot testing are presented.Material and methods: The audit utilizes a specially designed, commercially available anthropomorphic phantom capable of accommodating a small volume ion chamber (IC) in four locations (three in planning target volumes (PTVs) and one in an organ at risk (OAR)) and a Gafchromic film in a coronal plane for the absorbed dose to water and two-dimensional dose distribution measurements, respectively. The audit consists of a pre-visit and on-site phases. The pre-visit phase is carried out remotely and includes a treatment planning task and a set of computational exercises. The on-site phase aims at comparing the treatment planning system (TPS) calculations with measurements in the anthropomorphic phantom following an end-to-end approach. Two main aspects were tested in the pilot study: feasibility of the planning constraints and the accuracy of IC and film results in comparison with TPS calculations. Treatment plan quality was scored from 0 to 100. Results: Forty-two treatment plans were submitted by 14 institutions from 10 countries, with 79% of them having a plan quality score over 90. Seventeen sets of IC measurement results were collected, and the average measured to calculated dose ratio was 0.988 ± 0.016 for PTVs and 1.020 ± 0.029 for OAR. For 13 film measurement results, the average gamma passing rate was 94.1% using criteria of 3%/3 mm, 20% threshold and global gamma.Conclusions: The audit methodology was proved to be feasible and ready to be adopted by national dosimetry audit networks for local implementation.
Authors: Wolfgang Lechner; Rodolfo Alfonso; Mehenna Arib; M Saiful Huq; Anas Ismail; Rajesh Kinhikar; José M Lárraga-Gutiérrez; Karthick Raj Mani; Nkosingiphile Maphumulo; Otto A Sauer; Shaima Shoeir; Sivalee Suriyapee; Karen Christaki Journal: Med Phys Date: 2022-07-08 Impact factor: 4.506