Central Axis Percentage Depth-Dose in a Water Phantom Irradiated by Conventional X-rays

Water Phantom 속 Conventional X-ray 중심축상의 깊이 선량 백분율

  • Kim, Wuon-Shik (Radiation Laboratory, Korea Standards Research Institute) ;
  • Hah, Suck-Ho (Radiation Laboratory, Korea Standards Research Institute) ;
  • Hwang, Sun-Tae (Radiation Laboratory, Korea Standards Research Institute) ;
  • Oh, Jang-Jin (Department of Physics, Chungnam National University) ;
  • Jun, Jae-Shik (Department of Physics, Chungnam National University)
  • 김원식 (한국표준연구소 방사선연구실) ;
  • 하석호 (한국표준연구소 방사선연구실) ;
  • 황선태 (한국표준연구소 방사선연구실) ;
  • 오장진 (충남대학교 자연과학대학 물리학과) ;
  • 전재식 (충남대학교 자연과학대학 물리학과)
  • Published : 1987.06.15

Abstract

Central axis percentage depth-doses, P(%), were measured at the points from the 2.5cm depth of reference point to 20 cm depth with 2.5 cm interval. Distance from the X-ray target to the water phantom($30{\times}30{\times}30cm^3$) surface was 1 m, and at this point three different beam sizes of $5cm{\phi},\;10cm{\phi},\;and\;15cm{\phi}$ were used. While the X-ray tube voltage varied from 150 to 250 kV, the tube current remained constant at 5 mA. Absorbed dose rate in water, $\dot{D}_w$, was determined using the air kerma calibration factor, $N_k$, which was derived from the exposure calibration factor, $N_x$, of the NE 2571 ion chamber. The reference exposure rate, $\dot{X}_c$, was measured using the Exradin A-2 ion chamber calibrated at ETL, Japan. The half value layers of the X-rays determined to meet ETL calibration qualities. The absorbed dose rates determined at the calibration point were compared to the values obtained from Burlin's general cavity theory, and the percentage depth-dose values determined from $N_k$ showed a good agreement with the values of the published depth dose data(BJR Suppl. 17).

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