{"title":"蒙特卡罗计算的氦、碳和氖离子束的光束质量和微扰校正因子。","authors":"Yuka Urago, Makoto Sakama, Dousatsu Sakata, Tetsurou Katayose, Weishan Chang","doi":"10.1002/mp.70024","DOIUrl":null,"url":null,"abstract":"<div>\n \n \n <section>\n \n <h3> Purpose</h3>\n \n <p>A new technique, multi-ion radiotherapy, which uses He, O, and Ne ions in addition to C ions, has been proposed, though there is still limited information on the dosimetric quantities, such as the beam quality and perturbation correction factors, necessary to determine the absorbed dose-to-water for various ion species. In this study, beam-quality correction factors, <i>k</i><sub>Q</sub>, for He, C, and Ne ions in five types of ionization chambers were derived through Monte Carlo simulations. Additionally, perturbation effects attributed to the ionization chambers were analyzed in detail, and differences in these effects across chamber types and ions were clarified.</p>\n </section>\n \n <section>\n \n <h3> Methods</h3>\n \n <p>The <i>k</i><sub>Q</sub> values for 150 MeV/u-He, 290 MeV/u-C, and 400 MeV/u-Ne ions were evaluated using the Geant4 Monte Carlo code. The <i>f</i><sub>Q</sub> (the product of the water-to-air stopping power ratio and the perturbation correction factor) was obtained using the absorbed doses to water and to air inside the active volume of the ionization chamber. The <i>k</i><sub>Q</sub> values were then calculated from the <i>f</i><sub>Q</sub> and the literature-extracted factors, <span></span><math>\n <semantics>\n <msub>\n <mi>f</mi>\n <msub>\n <mi>Q</mi>\n <mn>0</mn>\n </msub>\n </msub>\n <annotation>${f_{{Q_0}}}$</annotation>\n </semantics></math> and <i>W</i><sub>air</sub>. To evaluate individual perturbation effects, each chamber component (such as the central electrode, wall, and stem in the modeled chambers) was replaced by water in turn, and the dose was recalculated for each modified geometry. From the ratio of these doses, the contribution of each component to the perturbation effect was estimated.</p>\n </section>\n \n <section>\n \n <h3> Results</h3>\n \n <p>The derived <i>k</i><sub>Q</sub> values were consistent with the code of practice for dosimetry, the revised TRS-398, and varied slightly with the ion species, from He to Ne ions. Additionally, the <i>k</i><sub>Q</sub> values increased by up to 1% compared with the current protocol values, particularly in plane-parallel chambers. Analysis of contributions to the perturbation factors revealed that the perturbation effect due to the cavity, <i>P</i><sub>cav</sub>, is significantly greater for light ions than for protons and had the most substantial impact among the evaluated individual perturbation factors.</p>\n </section>\n \n <section>\n \n <h3> Conclusions</h3>\n \n <p>The revision of <i>k</i><sub>Q</sub> values for light ions may result in the absorbed dose-to-water varying by up to 1% compared with doses calculated using the currently recommended <i>k</i><sub>Q</sub> values. At the current stage, it has been confirmed that common <i>k</i><sub>Q</sub> values can be applied to light ions from He to Ne in both Farmer and Markus type ionization chambers.</p>\n </section>\n </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 10","pages":""},"PeriodicalIF":3.2000,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Monte Carlo–calculated beam–quality and perturbation correction factors for helium–, carbon–, and neon–ion beams\",\"authors\":\"Yuka Urago, Makoto Sakama, Dousatsu Sakata, Tetsurou Katayose, Weishan Chang\",\"doi\":\"10.1002/mp.70024\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div>\\n \\n \\n <section>\\n \\n <h3> Purpose</h3>\\n \\n <p>A new technique, multi-ion radiotherapy, which uses He, O, and Ne ions in addition to C ions, has been proposed, though there is still limited information on the dosimetric quantities, such as the beam quality and perturbation correction factors, necessary to determine the absorbed dose-to-water for various ion species. In this study, beam-quality correction factors, <i>k</i><sub>Q</sub>, for He, C, and Ne ions in five types of ionization chambers were derived through Monte Carlo simulations. Additionally, perturbation effects attributed to the ionization chambers were analyzed in detail, and differences in these effects across chamber types and ions were clarified.</p>\\n </section>\\n \\n <section>\\n \\n <h3> Methods</h3>\\n \\n <p>The <i>k</i><sub>Q</sub> values for 150 MeV/u-He, 290 MeV/u-C, and 400 MeV/u-Ne ions were evaluated using the Geant4 Monte Carlo code. The <i>f</i><sub>Q</sub> (the product of the water-to-air stopping power ratio and the perturbation correction factor) was obtained using the absorbed doses to water and to air inside the active volume of the ionization chamber. The <i>k</i><sub>Q</sub> values were then calculated from the <i>f</i><sub>Q</sub> and the literature-extracted factors, <span></span><math>\\n <semantics>\\n <msub>\\n <mi>f</mi>\\n <msub>\\n <mi>Q</mi>\\n <mn>0</mn>\\n </msub>\\n </msub>\\n <annotation>${f_{{Q_0}}}$</annotation>\\n </semantics></math> and <i>W</i><sub>air</sub>. To evaluate individual perturbation effects, each chamber component (such as the central electrode, wall, and stem in the modeled chambers) was replaced by water in turn, and the dose was recalculated for each modified geometry. From the ratio of these doses, the contribution of each component to the perturbation effect was estimated.</p>\\n </section>\\n \\n <section>\\n \\n <h3> Results</h3>\\n \\n <p>The derived <i>k</i><sub>Q</sub> values were consistent with the code of practice for dosimetry, the revised TRS-398, and varied slightly with the ion species, from He to Ne ions. Additionally, the <i>k</i><sub>Q</sub> values increased by up to 1% compared with the current protocol values, particularly in plane-parallel chambers. Analysis of contributions to the perturbation factors revealed that the perturbation effect due to the cavity, <i>P</i><sub>cav</sub>, is significantly greater for light ions than for protons and had the most substantial impact among the evaluated individual perturbation factors.</p>\\n </section>\\n \\n <section>\\n \\n <h3> Conclusions</h3>\\n \\n <p>The revision of <i>k</i><sub>Q</sub> values for light ions may result in the absorbed dose-to-water varying by up to 1% compared with doses calculated using the currently recommended <i>k</i><sub>Q</sub> values. At the current stage, it has been confirmed that common <i>k</i><sub>Q</sub> values can be applied to light ions from He to Ne in both Farmer and Markus type ionization chambers.</p>\\n </section>\\n </div>\",\"PeriodicalId\":18384,\"journal\":{\"name\":\"Medical physics\",\"volume\":\"52 10\",\"pages\":\"\"},\"PeriodicalIF\":3.2000,\"publicationDate\":\"2025-09-18\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Medical physics\",\"FirstCategoryId\":\"3\",\"ListUrlMain\":\"https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.70024\",\"RegionNum\":2,\"RegionCategory\":\"医学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Medical physics","FirstCategoryId":"3","ListUrlMain":"https://aapm.onlinelibrary.wiley.com/doi/10.1002/mp.70024","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING","Score":null,"Total":0}
Monte Carlo–calculated beam–quality and perturbation correction factors for helium–, carbon–, and neon–ion beams
Purpose
A new technique, multi-ion radiotherapy, which uses He, O, and Ne ions in addition to C ions, has been proposed, though there is still limited information on the dosimetric quantities, such as the beam quality and perturbation correction factors, necessary to determine the absorbed dose-to-water for various ion species. In this study, beam-quality correction factors, kQ, for He, C, and Ne ions in five types of ionization chambers were derived through Monte Carlo simulations. Additionally, perturbation effects attributed to the ionization chambers were analyzed in detail, and differences in these effects across chamber types and ions were clarified.
Methods
The kQ values for 150 MeV/u-He, 290 MeV/u-C, and 400 MeV/u-Ne ions were evaluated using the Geant4 Monte Carlo code. The fQ (the product of the water-to-air stopping power ratio and the perturbation correction factor) was obtained using the absorbed doses to water and to air inside the active volume of the ionization chamber. The kQ values were then calculated from the fQ and the literature-extracted factors, and Wair. To evaluate individual perturbation effects, each chamber component (such as the central electrode, wall, and stem in the modeled chambers) was replaced by water in turn, and the dose was recalculated for each modified geometry. From the ratio of these doses, the contribution of each component to the perturbation effect was estimated.
Results
The derived kQ values were consistent with the code of practice for dosimetry, the revised TRS-398, and varied slightly with the ion species, from He to Ne ions. Additionally, the kQ values increased by up to 1% compared with the current protocol values, particularly in plane-parallel chambers. Analysis of contributions to the perturbation factors revealed that the perturbation effect due to the cavity, Pcav, is significantly greater for light ions than for protons and had the most substantial impact among the evaluated individual perturbation factors.
Conclusions
The revision of kQ values for light ions may result in the absorbed dose-to-water varying by up to 1% compared with doses calculated using the currently recommended kQ values. At the current stage, it has been confirmed that common kQ values can be applied to light ions from He to Ne in both Farmer and Markus type ionization chambers.
期刊介绍:
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