Dose profile measurement using an imaging plate: Evaluation of filters using Monte Carlo simulation of 4 MV x-rays

Masatoshi Hashimoto, Tetsuya Tomita, Koichi Sawada, Toshioh Fujibuchi, Teiji Nishio, Keiichi Nakagawa

研究成果: ジャーナルへの寄稿記事

抄録

Computed radiography (CR) is gradually replacing film. The application of CR for two-dimensional profiles and off-axis ratio (OAR) measurement using an imaging plate (IP) in a CR system is currently under discussion. However, a well known problem for IPs in dosimetry is that they use high atomic number (Z) materials, such as Ba, which have an energy dependency in a photon interaction. Although there are some reports that it is possible to compensate for the energy dependency with metal filters, the appropriate thicknesses of these filters and where they should be located have not been investigated. The purpose of this study is to find the most suitable filter for use with an IP as a dosimetric tool. Monte Carlo simulation (Geant4 8.1) was used to determine the filter to minimize the measurement error in OAR measurements of 4 MV x-rays. In this simulation, the material and thickness of the filter and distance between the IP and the filter were varied to determine most suitable filter conditions that gave the best fit to the MC calculated OAR in water. With regard to changing the filter material, we found that using higher Z and higher density material increased the effectiveness of the filter. Also, increasing the distance between the filter and the IP reduced the effectiveness, whereas increasing the thickness of the filter increased the effectiveness. The result of this study showed that the most appropriate filter conditions consistent with the calculated OAR in water were the ones with the IP sandwiched between two 2 mm thick lead filters at a distance of 5 mm from the IP or the IP sandwiched directly between two 1 mm lead filters. Using these filters, we measured the OAR at 10 cm depth with 100 cm source-to-surface distance and surface 10×10 cm2 field size. The results of this measurement represented that it is possible to achieve measurements with less than within 2.0% and 2.0% in the field and with less than 1.1% and 0.6% out of the field by using 2 and 1 mm lead filters, respectively.

元の言語英語
記事番号045101
ジャーナルReview of Scientific Instruments
80
発行部数4
DOI
出版物ステータス出版済み - 1 1 2009
外部発表Yes

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Imaging techniques
filters
X rays
dosage
evaluation
profiles
Radiography
x rays
simulation
Lead
radiography
Monte Carlo simulation
Measurement errors
Dosimetry
Water
Photons
Metals
water
dosimeters
energy

All Science Journal Classification (ASJC) codes

  • Instrumentation

これを引用

Dose profile measurement using an imaging plate : Evaluation of filters using Monte Carlo simulation of 4 MV x-rays. / Hashimoto, Masatoshi; Tomita, Tetsuya; Sawada, Koichi; Fujibuchi, Toshioh; Nishio, Teiji; Nakagawa, Keiichi.

:: Review of Scientific Instruments, 巻 80, 番号 4, 045101, 01.01.2009.

研究成果: ジャーナルへの寄稿記事

Hashimoto, Masatoshi ; Tomita, Tetsuya ; Sawada, Koichi ; Fujibuchi, Toshioh ; Nishio, Teiji ; Nakagawa, Keiichi. / Dose profile measurement using an imaging plate : Evaluation of filters using Monte Carlo simulation of 4 MV x-rays. :: Review of Scientific Instruments. 2009 ; 巻 80, 番号 4.
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abstract = "Computed radiography (CR) is gradually replacing film. The application of CR for two-dimensional profiles and off-axis ratio (OAR) measurement using an imaging plate (IP) in a CR system is currently under discussion. However, a well known problem for IPs in dosimetry is that they use high atomic number (Z) materials, such as Ba, which have an energy dependency in a photon interaction. Although there are some reports that it is possible to compensate for the energy dependency with metal filters, the appropriate thicknesses of these filters and where they should be located have not been investigated. The purpose of this study is to find the most suitable filter for use with an IP as a dosimetric tool. Monte Carlo simulation (Geant4 8.1) was used to determine the filter to minimize the measurement error in OAR measurements of 4 MV x-rays. In this simulation, the material and thickness of the filter and distance between the IP and the filter were varied to determine most suitable filter conditions that gave the best fit to the MC calculated OAR in water. With regard to changing the filter material, we found that using higher Z and higher density material increased the effectiveness of the filter. Also, increasing the distance between the filter and the IP reduced the effectiveness, whereas increasing the thickness of the filter increased the effectiveness. The result of this study showed that the most appropriate filter conditions consistent with the calculated OAR in water were the ones with the IP sandwiched between two 2 mm thick lead filters at a distance of 5 mm from the IP or the IP sandwiched directly between two 1 mm lead filters. Using these filters, we measured the OAR at 10 cm depth with 100 cm source-to-surface distance and surface 10×10 cm2 field size. The results of this measurement represented that it is possible to achieve measurements with less than within 2.0{\%} and 2.0{\%} in the field and with less than 1.1{\%} and 0.6{\%} out of the field by using 2 and 1 mm lead filters, respectively.",
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AU - Hashimoto, Masatoshi

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AU - Nishio, Teiji

AU - Nakagawa, Keiichi

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