Quenching Effect, Signal to Noise, Contrast to Noise Ratios on Scintillator Screens for Proton Beam Dosimetry System
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<jats:p> There has been dosimetry using scintillator screen for proton quality assurance recently. To develop a proton beam dosimetry system using scintillator, we evaluated the dosimetric properties and imaging quality for three kinds of scintillator screens. Proton beam ranges of 6, 9, and 12 g/cm<jats:sup>2</jats:sup> were determined in a water phantom using an ion chamber. Beam current was optimized about each scintillator screen at proton beam ranges of 6, 9, and 12 g/cm<jats:sup>2</jats:sup>. Dose rate was in beam condition of proton treatment. For comparison of the dosimetric properties, the quenching correction factors and standard deviations for the scintillator screens (C<jats:sub>6</jats:sub>H<jats:sub>6</jats:sub>, Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S:Tb, and Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S) were obtained using the relation between the light yield (scintillator-relative output) and the dose distribution (diode-relative output). The image qualities for the scintillator screens were compared, using the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR), in consideration of the physical properties of the scintillator materials. After correction of the quenching effect, the correction factor for scintillator screen Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S:Tb was the lowest, at 0.004 g/(cm<jats:sup>2</jats:sup> MeV). The standard deviations of the difference between the yields measured by the scintillator screens and the diode detector averaged 1, 1.3, and 1.3, respectively, at all of the ranges from origin to the peak position. The dosimetric properties of scintillator screens were no large difference. The SNRs of the scintillator screens (C<jats:sub>6</jats:sub>H<jats:sub>6</jats:sub>, Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S:Tb, and Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S) averaged 28.67, 40.18, and 24.56, respectively, at all ranges. The CNRs of the scintillator screens (C<jats:sub>6</jats:sub>H<jats:sub>6</jats:sub>, Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S:Tb, and Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S) averaged 0.44, 0.33, and 0.42, respectively, at all ranges. The highest SNR and the lowest CNR of scintillator screen Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S:Tb were more excellent than those of the other scintillator screens. We evaluated the dosimetric properties in terms of the quenching-effect correction factors, standard deviations image qualities in terms of SNR and CNR about scintillator screens. The correction factor and standard deviation for scintillator screens made no large difference. Scintillator screen Gd<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>S:Tb had the highest value of SNR and the lowest value of CNR, and accordingly was considered to be best in proton beam imaging quality. </jats:p>
収録刊行物
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- Japanese journal of applied physics : JJAP
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Japanese journal of applied physics : JJAP 51 (4), 046401-, 2012-04
Tokyo : The Japan Society of Applied Physics
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詳細情報 詳細情報について
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- CRID
- 1520572357043671680
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- NII論文ID
- 40019231354
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- NII書誌ID
- AA12295836
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- ISSN
- 00214922
- 13474065
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- NDL書誌ID
- 023588122
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- 本文言語コード
- en
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- NDL 雑誌分類
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- ZM35(科学技術--物理学)
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- データソース種別
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- NDL
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