Water Phantom 속 Conventional X-ray 중심축상의 깊이 선량 백분율
김원식;하석호;황선태;오장진;전재식;
Central Axis Percentage Depth-Dose in a Water Phantom Irradiated by Conventional X-rays
Kim, Wuon-Shik;Hah, Suck-Ho;Hwang, Sun-Tae;Oh, Jang-Jin;Jun, Jae-Shik;
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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