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Experimental verification of gain drop due to general ion recombination for a carbon-ion pencil beam
https://repo.qst.go.jp/records/47603
https://repo.qst.go.jp/records/47603b0e3fc86-19b4-4ac2-a088-107a6d7068e8
| Item type | 学術雑誌論文 / Journal Article(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2017-01-04 | |||||
| タイトル | ||||||
| タイトル | Experimental verification of gain drop due to general ion recombination for a carbon-ion pencil beam | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | journal article | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Tansho, Ryohei
× Tansho, Ryohei× Furukawa, Takuji× Hara, Yousuke× Mizushima, Kota× Saotome, Naoya× Saraya, Yuichi× Shirai, Toshiyuki× Noda, Koji× 丹正 亮平× 古川 卓司× 原 洋介× 水島 康太× 早乙女 直也× 皿谷 有一× 白井 敏之× 野田 耕司 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Purpose: Accurate dose measurement in radiotherapy is critically dependent on correction for gain drop, which is the difference of the measured current from the ideal saturation current due to general ion recombination. Although a correction method based on the Boag theory has been employed, the theory assumes that ionized charge density in an ionization chamber (IC) is spatially uniform throughout the irradiation volume. For particle pencil beam scanning, however, the charge density is not uniform, because the fluence distribution of a pencil beam is not uniform. The aim of this study was to verify the effect of the nonuniformity of ionized charge density on the gain drop due to general ion recombination. Methods: The authors measured the saturation curve, namely the applied voltage versus measured current, using a large plane-parallel IC and 24-channel parallel-plate IC with concentric electrodes. To verify the effect of the nonuniform ionized charge density on the measured saturation curve, we calculated the saturation curve using a method which takes into account the nonuniform ionized charge density and compared it with the measured saturation curves. Results: Measurement values of the different saturation curves in the different channels of the concentric electrodes differed, and were consistent with the calculated values. The saturation curves measured by the large plane-parallel IC were also consistent with the calculation results, including the estimation error of beam size and of setup misalignment. Although the impact of the nonuniform ionized charge density on the gain drop was clinically negligible with the conventional beam intensity, it was expected that the impact would increase with higher ionized charge density. Conclusions: For pencil beam scanning, the assumption of the conventional Boag theory is not valid. Furthermore, the nonuniform ionized charge density affects the prediction accuracy of gain drop when the ionized charge density is increased by a higher dose rate and/or lower beam size. |
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| 書誌情報 |
Medical Physics 巻 43, 号 2, p. 635-642, 発行日 2016-02 |
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| 出版者 | ||||||
| 出版者 | AIP publishing | |||||
| ISSN | ||||||
| 収録物識別子タイプ | ISSN | |||||
| 収録物識別子 | 0094-2405 | |||||
