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KMID : 1038720140250040255
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Progress in Medical Physics
2014 Volume.25 No. 4 p.255 ~ p.263
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Feasibility Study of the microDiamond Detector for Measurement of Small Field Photon Beam
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Lee Chang-Yeol
Kim Woo-Chul
Kim Hun-Jeong
Huh Do
Ji Young-Hoon
Kim Kum-Bae
Lee Sang-Hoon
Min Chul-Kee
Jo Gwang-Hwan
Shin Dong-Oh
Kim Seong-Hoon
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Abstract
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The dosimetry of very small fields is challenging for several reasons including a lack of lateral electronic equilibrium, large dose gradients, and the size of detector in respect to the field size. The objective of this work was to evaluate the suitability of a new commercial synthetic diamond detector, namely, the PTW 60019 microDiamond, for the small field dosimetry in cyberknife photon beams of 6 different collimator size (from 5 mm to 30 mm). Measurements included dose linearity, dose rate dependence, output factors (OF), percentage depth doses (PDD) and off center ratio (OCR). The results were compared to those of pinpoint ionization chamber, diamond detector, microLion liquid Ionization chamber and diode detector. The dose linearity results for the microDiamond detector showed good linearly proportional to dose. The microDiamond detector showed little dose rate dependency throughout the range of 100~600 MU/min, while microLion liquid Ionization chamber showed a significant discrepancy of approximately 5.8%. The OF measured with microDiamond detector agreed within 3.8% with those measured with diode. PDD curves measured with silicon diode and diamond detector agreed well for all the field sizes. In particular, slightly sharper penumbras are obtained by the microDiamond detector, indicating a good spatial resolution. The results obtained confirm that the new PTW 60019 microDiamond detector is suitable candidate for application in small radiation fields dosimetry.
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KEYWORD
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microDiamond detector, Small field, Dosimetry
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