Tania Santos1, Maria do Carmo Lopes2, Eduard Gershkevitsh3, Filipa Vinagre4, David Faria5, Liliana Carita6, Miguel Pontes7, Sandra Vieira8, Esmeralda Poli9, Sofia Faustino10, Filipa Ribeiro11, Mauro Trindade12, Fernanda Ponte13, Carlos Marcelino14, Cláudio Batista15, Susana Oliveira16, Rita Figueira17, Joana Lencart18, Ester Gallego Diaz19, Katia Jacob20, Sandra Brás21, Rui Pirraco22, Joanna Izewska23. 1. Departamento de Física, Universidade de Coimbra, Coimbra, Portugal; Serviço de Física Médica, IPOCFG, E.P.E., Coimbra, Portugal. Electronic address: taniafssantos@gmail.com. 2. Serviço de Física Médica, IPOCFG, E.P.E., Coimbra, Portugal. 3. North Estonia Medical Centre, Tallinn, Estonia. 4. CHUC, E.P.E., Coimbra, Portugal. 5. Lenitudes Medical Center and Research, Sta Maria da Feira, Portugal. 6. IPOLFG, E.P.E., Lisboa, Portugal. 7. JCS - Centro Oncológico Dra Natália Chaves, Carnaxide, Portugal. 8. Fundação Champalimaud, Lisboa, Portugal. 9. CHULN-Hospital de Sta Maria, Lisboa, Portugal. 10. Hospital da Luz, Lisboa, Portugal. 11. CHBM, E.P.E., Barreiro, Portugal. 12. CHTMAD, E.P.E., Vila Real, Portugal. 13. Instituto CUF Porto, Porto, Portugal. 14. Lenicare, Évora, Portugal. 15. JCS - Clínica de Radioncologia de Santarém, Santarém, Portugal. 16. JCS - Clínica de Radioncologia do Algarve, Faro, Portugal. 17. CHUSJ, E.P.E., Porto, Portugal. 18. IPOPFG, E.P.E., Porto, Portugal. 19. JCS - Clínica de Radioncologia da Madeira, Madeira, Portugal. 20. Hospital CUF Descobertas, Lisboa, Portugal. 21. JCS - Clínica de Radioncologia Madalena Paiva, Açores, Portugal. 22. Hospital de Braga, Braga, Portugal. 23. Dosimetry and Medical Radiation Physics Section, International Atomic Energy Agency, Vienna, Austria.
Abstract
PURPOSE: The IAEA newly developed "end-to-end" audit methodology for on-site verification of IMRT dose delivery has been carried out in Portugal in 2018. The main goal was to evaluate the physical aspects of the head and neck (H&N) cancer IMRT treatments. This paper presents the national results. METHODS: All institutions performing IMRT treatments in Portugal, 20 out of 24, have voluntarily participated in this audit. Following the adopted methodology, a Shoulder, Head and Neck End-to-End phantom (SHANE) - that mimics an H&N region, underwent all steps of an IMRT treatment, according to the local practices. The measurements using an ionization chamber placed inside the SHANE phantom at four reference locations (three in PTVs and one in the spinal cord) and an EBT3 film positioned in a coronal plane were compared with calculated doses. FilmQA Pro software was used for film analysis. RESULTS: For ionization chamber measurements, the percent difference was within the specified tolerances of ±5% for PTVs and ±7% for the spinal cord in all participating institutions. Considering film analysis, gamma passing rates were on average 96.9%±2.9% for a criterion of 3%/3 mm, 20% threshold, all above the acceptance limit of 90%. CONCLUSIONS: The national results of the H&N IMRT audit showed a compliance between the planned and the delivered doses within the specified tolerances, confirming no major reasons for concern. At the same time the audit identified factors that contributed to increased uncertainties in the IMRT dose delivery in some institutions resulting in recommendations for quality improvement.
PURPOSE: The IAEA newly developed "end-to-end" audit methodology for on-site verification of IMRT dose delivery has been carried out in Portugal in 2018. The main goal was to evaluate the physical aspects of the head and neck (H&N) cancer IMRT treatments. This paper presents the national results. METHODS: All institutions performing IMRT treatments in Portugal, 20 out of 24, have voluntarily participated in this audit. Following the adopted methodology, a Shoulder, Head and Neck End-to-End phantom (SHANE) - that mimics an H&N region, underwent all steps of an IMRT treatment, according to the local practices. The measurements using an ionization chamber placed inside the SHANE phantom at four reference locations (three in PTVs and one in the spinal cord) and an EBT3 film positioned in a coronal plane were compared with calculated doses. FilmQA Pro software was used for film analysis. RESULTS: For ionization chamber measurements, the percent difference was within the specified tolerances of ±5% for PTVs and ±7% for the spinal cord in all participating institutions. Considering film analysis, gamma passing rates were on average 96.9%±2.9% for a criterion of 3%/3 mm, 20% threshold, all above the acceptance limit of 90%. CONCLUSIONS: The national results of the H&N IMRT audit showed a compliance between the planned and the delivered doses within the specified tolerances, confirming no major reasons for concern. At the same time the audit identified factors that contributed to increased uncertainties in the IMRT dose delivery in some institutions resulting in recommendations for quality improvement.