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Practical Output Dosimetry with Undefined $N_{dw}{^{Co-60}}$ of Cylindrical Ionization Chamber for High Energy Photon Beams of Linear Accelerator  

Oh, Young-Kee (Department of Radiation Oncology, School of Medicine, Keimyung University)
Choi, Tae-Jin (Department of Medical Engineering and Physics in Medicine, School of Medicine, Keimyung University)
Song, Ju-Young (Department of Radiation Oncology, Chonnam National University Hospital)
Publication Information
Progress in Medical Physics / v.23, no.2, 2012 , pp. 114-122 More about this Journal
Abstract
For the determination of absorbed dose to water from a linear accelerator photon beams, it needs a exposure calibration factor $N_x$ or air kerma calibration factor $N_k$ of air ionization chamber. We used the exposure calibration factor $N_x$ to find the absorbed dose calibration factors of water in a reference source through the TG-21 and TRS-277 protocol. TG-21 used for determine the absorbed dose in accuracy, but it required complex calculations including the chamber dependent factors. The authors obtained the absorbed dose calibration factor $N_{dw}{^{Co-60}}$ for reduce the complex calculations with unknown $N_{dw}$ only with $N_x$ or $N_k$ calibration factor in a TM31010 (S/N 1055, 1057) ionization chambers. The results showed the uncertainty of calculated $N_{dw}$ of IC-15 which was known the $N_x$ and $N_{dw}$ is within -0.6% in TG-21, but 1.0% in TRS-277. and TM31010 was compared the $N_{dw}$ of SSDL to that of PSDL as shown the 0.4%, -2.8% uncertainty, respectively. The authors experimented with good agreement the calculated $N_{dw}$ is reliable for cross check the discrepancy of the calibration factor with unknown that of TM31010 and IC-15 chamber.
Keywords
Exposure calculation factor $N_x$; Air kerma $N_k$; Absorbed dose calculation factor $N_{dw}$;
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