title: Performance of two commercial electron beam algorithms over regions close to the lung-mediastinum interface, against Monte Carlo simulation and point dosimetry in virtual and anthropomorphic phantoms.
abstract: Electron radiotherapy is applied to treat the chest wall close to the mediastinum. The performance of the GGPB and eMC algorithms implemented in the Varian Eclipse treatment planning system (TPS) was studied in this region for 9 and 16 MeV beams, against Monte Carlo (MC) simulations, point dosimetry in a water phantom and dose distributions calculated in virtual phantoms. For the 16 MeV beam, the accuracy of these algorithms was also compared over the lung-mediastinum interface region of an anthropomorphic phantom, against MC calculations and thermoluminescence dosimetry (TLD). In the phantom with a lung-equivalent slab the results were generally congruent, the eMC results for the 9 MeV beam slightly overestimating the lung dose, and the GGPB results for the 16 MeV beam underestimating the lung dose. Over the lung-mediastinum interface, for 9 and 16 MeV beams, the GGPB code underestimated the lung dose and overestimated the dose in water close to the lung, compared to the congruent eMC and MC results. In the anthropomorphic phantom, results of TLD measurements and MC and eMC calculations agreed, while the GGPB code underestimated the lung dose. Good agreement between TLD measurements and MC calculations attests to the accuracy of "full" MC simulations as a reference for benchmarking TPS codes. Application of the GGPB code in chest wall radiotherapy may result in significant underestimation of the lung dose and overestimation of dose to the mediastinum, affecting plan optimization over volumes close to the lung-mediastinum interface, such as the lung or heart.
authors.affiliation: Department of Oncology, Unit of Radiotherapy, Tampere University Hospital, P.O. Box 2000, FI-33521 Tampere, Finland; Department of Electronics and Communications Engineering, Tampere University of Technology, P.O. Box 527, FI-33101 Tampere, Finland. Electronic address: jarkko.ojala@pshp.fi.
authors.forename: J
authors.initials: J
authors.lastname: Ojala
authors.affiliation: Department of Oncology, Unit of Radiotherapy, Tampere University Hospital, P.O. Box 2000, FI-33521 Tampere, Finland; Department of Electronics and Communications Engineering, Tampere University of Technology, P.O. Box 527, FI-33101 Tampere, Finland; Department of Medical Physics, Medical Imaging Center, Tampere University Hospital, P.O. Box 2000, FI-33521 Tampere, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Hyödynmaa
authors.affiliation: Radiation Protection Unit, Directorate-General for Energy, European Commission, L-2920, Luxembourg.
authors.forename: R
authors.initials: R
authors.lastname: Barańczyk
authors.affiliation: Centre of Oncology, Kraków Division, Kraków, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Góra
authors.affiliation: Centre of Oncology, Kraków Division, Kraków, Poland; Institute of Nuclear Physics, Polish Academy of Sciences, Kraków, Poland.
authors.forename: M P R
authors.initials: MP
authors.lastname: Waligórski
mesh_terms: D000465:Algorithms; D004583:Electrons / Q000627:therapeutic use*; D006801:Humans; D008168:Lung / Q000528:radiation effects*; D008482:Mediastinum / Q000528:radiation effects*; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*
keywords: Dose calculation; Electron beam radiotherapy; Monte Carlo; TLD