Kilian-Simon Baumann, Ana Lourenço, Jörg Wulff, Gloria Vilches-Freixas, Hugo Palmans
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 Approach: Monte Carlo simulations were performed to calculate the chamber-specific factor f<sub>Q</sub>in monoenergetic proton beams for six different plane-parallel ionization chambers while positioning the chambers with a) their reference point and b) their effective point of measurement accounting for the water equivalent thickness of the entrance window.
Main results: For all ionization chamber models investigated in this study, the difference in f<sub>Q</sub>between both positioning approaches was larger for steeper dose gradients and bigger differences between the geometrical thickness and water-equivalent thickness of the entrance window. The largest effect was 1.2% for the IBA PPC-05 ionization chamber at an energy of 60 MeV.
Significance: The positioning of plane-parallel ionization chambers in proton beams has a systematic impact on the f<sub>Q</sub>factor. This is especially of relevance for the k<sub>Q,Q0</sub>factors presented in the recently updated TRS-398 Code of Practice (CoP) from IAEA. The background is that a positioning with the effective point of measurement is prescribed in TRS-398 CoP, however, all Monte Carlo derived data that have been employed for the update are based on a positioning of the ionization chambers with their reference point. Hence, the updated k<sub>Q,Q0</sub>factors for plane-parallel ionization chambers in proton beams are subject to systematic errors that are as large as 0.5%.
.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3000,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics in medicine and biology","FirstCategoryId":"5","ListUrlMain":"https://doi.org/10.1088/1361-6560/ad9e7c","RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, BIOMEDICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Objective: To investigate the impact of the positioning of plane-parallel ionization chambers in proton beams on the calculation of the chamber-specific factor fQand, hence, the beam quality correction factor kQ,Q0.
Approach: Monte Carlo simulations were performed to calculate the chamber-specific factor fQin monoenergetic proton beams for six different plane-parallel ionization chambers while positioning the chambers with a) their reference point and b) their effective point of measurement accounting for the water equivalent thickness of the entrance window.
Main results: For all ionization chamber models investigated in this study, the difference in fQbetween both positioning approaches was larger for steeper dose gradients and bigger differences between the geometrical thickness and water-equivalent thickness of the entrance window. The largest effect was 1.2% for the IBA PPC-05 ionization chamber at an energy of 60 MeV.
Significance: The positioning of plane-parallel ionization chambers in proton beams has a systematic impact on the fQfactor. This is especially of relevance for the kQ,Q0factors presented in the recently updated TRS-398 Code of Practice (CoP) from IAEA. The background is that a positioning with the effective point of measurement is prescribed in TRS-398 CoP, however, all Monte Carlo derived data that have been employed for the update are based on a positioning of the ionization chambers with their reference point. Hence, the updated kQ,Q0factors for plane-parallel ionization chambers in proton beams are subject to systematic errors that are as large as 0.5%.
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期刊介绍:
The development and application of theoretical, computational and experimental physics to medicine, physiology and biology. Topics covered are: therapy physics (including ionizing and non-ionizing radiation); biomedical imaging (e.g. x-ray, magnetic resonance, ultrasound, optical and nuclear imaging); image-guided interventions; image reconstruction and analysis (including kinetic modelling); artificial intelligence in biomedical physics and analysis; nanoparticles in imaging and therapy; radiobiology; radiation protection and patient dose monitoring; radiation dosimetry