| The Comparison the Output dose of a Linear Accelerator Photon Beams by Using the
Ionization Chamber IC-10 Series Through TG-21 Protocol to Postal Monitoring Output of
MDACC for One and Half Decade |
| IC-10계열의 이온전리함과 TG-21을 이용한 장기간 선형가속기의 출력선량 평가 비교 |
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최태진; 김진희; 김옥배 |
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| Abstract |
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This study is to provided the accuracy and stability of the output dose of linear accelerator photon
beams by using the IC-10 and IC-15 air ionization chambers through the Task Group 22
protocol. The gas absorbed dose calibration factor Ngas is determined using the Bragg-Gray
cavity theory for the air exposure calibration factor Nx of Co-60 gamma rays which is delivered
from manufacture through NBS calibration. The ionization chamber of IC-10 series composit the
Shonka C-552 material with density 1.76 g/ml which is equivalent to air material. the authors
provided the Awall from correction equation for air absorbed calibration factor Ngas and ion
recombination correction factor Aion from Pion analytic measurement. The absorbed dose in water
phantorm is derived from the Ngas including the correction factors mass stopping power ratio of
water to that of gas; ion recombination and replacement for 6 and 23 MV X rays; respectively.
The determined absorbed dose of water phantom exposed to a postal TLD block for output
evaluation in MDACC’s postal monitoring program. The results of comparisons of evaluated
absorbed dose to that of MDACC have shown the 1.000 ± 0.012 for 6 MV and 1.001 0.013
discrepancy for 23 MV X rays for a long term followed. This study shows the evaluated outputs for linear accelerator photon beams are very close to that of international output monitor with
small discrepancy of 1.3% for one and half decade. |
| Key Words:
Ngas, Nx, Output dose, TG-22, TLD monitor |
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