On the conversion of dose to bone to dose to water in radiotherapy treatment planning systems
Autor: | Edmond Sterpin, F. Crop, Hugo Palmans, Nick Reynaert, Iwan Kawrakow |
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Jazyk: | angličtina |
Rok vydání: | 2018 |
Předmět: |
lcsh:Medical physics. Medical radiology. Nuclear medicine
Electron density Materials science Dose to water lcsh:R895-920 Monte Carlo method Physics::Medical Physics lcsh:RC254-282 Imaging phantom 030218 nuclear medicine & medical imaging 03 medical and health sciences 0302 clinical medicine Dosimetry Stopping power (particle radiation) Radiology Nuclear Medicine and imaging Original Research Article Absorption (electromagnetic radiation) Monte Carlo TPS comparison Radiation Généralités Radiotherapy treatment planning lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens 030220 oncology & carcinogenesis Attenuation coefficient Atomic physics |
Zdroj: | Physics and Imaging in Radiation Oncology, 5 Physics and Imaging in Radiation Oncology, Vol 5, Iss, Pp 26-30 (2018) Physics and Imaging in Radiation Oncology |
Popis: | Background and purpose: Conversion factors between dose to medium (Dm,m) and dose to water (Dw,w) provided by treatment planning systems that model the patient as water with variable electron density are currently based on stopping power ratios. In the current paper it will be illustrated that this conversion method is not correct. Materials and methods: Monte Carlo calculations were performed in a phantom consisting of a 2 cm bone layer surrounded by water. Dw,w was obtained by modelling the bone layer as water with the electron density of bone. Conversion factors between Dw,w and Dm,m were obtained and compared to stopping power ratios and ratios of mass-energy absorption coefficients in regions of electronic equilibrium and interfaces. Calculations were performed for 6 MV and 20 MV photon beams. Results: In the region of electronic equilibrium the stopping power ratio of water to bone (1.11) largely overestimates the conversion obtained using the Monte Carlo calculations (1.06). In that region the MC dose conversion corresponds to the ratio of mass energy absorption coefficients. Near the water to bone interface, the MC ratio cannot be determined from stopping powers or mass energy absorption coefficients. Conclusion: Stopping power ratios cannot be used for conversion from Dm,m to Dw,w provided by treatment planning systems that model the patient as water with variable electron density, either in regions of electronic equilibrium or near interfaces. In regions of electronic equilibrium mass energy absorption coefficient ratios should be used. Conversions at interfaces require detailed MC calculations. SCOPUS: ar.j info:eu-repo/semantics/published |
Databáze: | OpenAIRE |
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