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KMID : 0384620090200020097
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Korean Journal of Medical Physics
2009 Volume.20 No. 2 p.97 ~ p.105
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Study on Absorbed Dose Determination of Electron Beam Quality for Cross-calibration with Plane-parallel Ionization Chamber
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Rah Jeong-Eun
Shin Dong-Oh
Park So-Hyun
Jeong Ho-Jin
Hwang Ui-Jung
Ahn Sung-Hwan
Lim Young-Kyung
Kim Dong-Wook
Yoon Myong-Geun
Shin Dong-Ho
Lee Se-Byeong
Suh Tae-Suk
Park Sung-Yong
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Abstract
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Absorbed dose to water based protocols recommended that plane-parallel chambers be calibrated against calibrated cylindrical chambers in a high energy electron beam with R50＞7 g/cm2 (E ?16 MeV). However, such high-energy electron beams are not available at all radiotherapy centers. In this study, we are compared the absorbed dose to water determined according to cross-calibration method in a high energy electron beam of 16 MeV and in electron beam energies of 12 MeV below the cross-calibration quality remark. Absorbed dose were performed for PTW 30013, Wellhofer FC65G Farmer type cylindrical chamber and for PTW 34001, Wellhofer PPC40 Roos type plane-parallel chamber. The cylindrical and the plane-parallel chamber to be calibrated are compared by alternately positioning each at reference depth, zref =0.6R50-0.1 in water phantom. The DW of plane-parallel chamber are derived using across-calibration method at high-energy electron beams of 16, 20 MeV. Then a good agreement is obtained the DW of plane-parallel chamber in 12 MeV. The agreement between 20 MeV and 12 MeV are within 0.2% for IAEA TRS-398.
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KEYWORD
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Electron beam, Absorbed dose to water calibration coefficient, Plane-parallel ionization chamber, Cross-calibration, Beam quality
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