Assessment of out-of-field doses in radiotherapy treatments of paediatric patients using Monte Carlo methods and measurements |
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| Affiliation: | 1. Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Campus Tecnológico e Nuclear, Estrada Nacional 10, km 139,7, 2695-066 Bobadela LRS, Portugal;2. Universidade de Lisboa, Faculdade de Ciências, Instituto de Biofísica e Engenharia Biomédica, Campo Grande, Lisboa 1749-016, Portugal;3. Escola Superior de Tecnologia da Saúde de Lisboa – Instituto Politécnico de Lisboa, Av. D. João II, lote 4.69.01, Lisboa 1990-096, Portugal;4. Escola Superior de Saúde Drº Lopes Dias – Instituto Politécnico de Castelo Branco, Campus da Talagueira, Avenida do Empresário, Castelo Branco 6000-767, Portugal;5. Serviço de Radioterapia, Instituto Português de Oncologia de Lisboa Francisco Gentil, R. Prof° Lima Basto, 1099-023 Lisboa, Portugal;6. Department of Medical Physics, Wisconsin Institutes for Medical Research, University of Wisconsin-Madison, 1111 Highland Ave., L5-176, Madison, WI 53705-2275, USA;7. Mediclinic City Hospital FZ L.L.C., PO Box 505004, Building 35&37, Dubai Healthcare City, Dubai, United Arab Emirates;8. Laboratório de Proteção e Segurança Radiológica, Instituto Superior Técnico, Campus Tecnológico e Nuclear, Estrada Nacional 10, km 139,7, 2695-066, Bobadela LRS, Portugal;1. Département de Physique Médicale, Centre de Recherche Nucléaire d''Alger, 2 Bd Frantz Fanon BP399 Alger RP, Algiers, Algeria;2. Service de Radiothérapie, Centre Pierre et Marie Curie, 1 Rue Battandier Place du 1er Mai, Algiers, Algeria;3. Service de Radiothérapie, Centre Anti-Cancer d''Oran, Oran, Algeria;1. Division of Medical Physics, Department of Information Technology and Medical Engineering, Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan;2. Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan;3. Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan;4. Kansai BNCT Medical Center, Osaka Medical College, 2-7 Daigaku-Machi, Takatsuki, Osaka 569-8686, Japan;5. Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2 Asashiro-nishi Kumatori-cho, Osaka 590-0494, Japan;1. Department of Physics, University of Zurich, Zurich, Switzerland;2. Radiotherapy Hirslanden, Hirslanden Medical Center, Aarau, Switzerland;1. Department of Radiological Technology, Yamaguchi University Hospital, 1-1-1 Minamikogushi, Ube 755-8505, Japan;2. Department of Health Sciences, Faculty of Life Sciences, Kumamoto University, 4-24-1 Kuhonji, Kumamoto 862-0976, Japan;1. Instituto de Física del Sur (IFISUR, UNS-CONICET), Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahía Blanca, Argentina;2. International Medical Centre, Centre for Radiotherapy, Dvanaest beba bb, 78000 Banja Luka, Bosnia and Herzegovina |
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| Abstract: | PurposeTo assess out-of-field doses in radiotherapy treatments of paediatric patients, using Monte Carlo methods to implement a new model of the linear accelerator validated against measurements and developing a voxelized anthropomorphic paediatric phantom.MethodsCT images of a physical anthropomorphic paediatric phantom were acquired and a dosimetric planning using a TPS was obtained. The CT images were used to perform the voxelization of the physical phantom using the ImageJ software and later implemented in MCNP. In order to validate the Monte Carlo model, dose measurements of the 6 MV beam and Linac with 120 MLC were made in a clinical setting, using ionization chambers and a water phantom. Afterwards TLD measurements in the physical anthropomorphic phantom were performed in order to assess the out-of-field doses in the eyes, thyroid, c-spine, heart and lungs.ResultsThe Monte Carlo model was validated for in-field and out-of-field doses with average relative differences below 3%. The average relative differences between TLD measurements and Monte Carlo is 14,3% whilst the average relative differences between TLD and TPS is 55,8%. Moreover, organs up to 22.5 cm from PTV center show TLD and MCNP6 relative differences and TLD and TPS relative differences up to 21.2% and 92.0%, respectively.ConclusionsOur study provides a novel model that could be used in clinical research, namely in dose evaluation outside the treatment fields. This is particularly relevant, especially in pediatric patients, for studying new radiotherapy treatment techniques, since it can be used to estimate the development of secondary tumours. |
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| Keywords: | Out-of-field doses Clinical measurements Monte Carlo methods Anthropomorphic paediatric phantom |
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