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Published on: May 9, 2014
The Measurement of the Air-Kerma Rate in Air and a Solid Phantom with Ionization Chambers for a 192Ir HDR
Jing Zeng1,2, Pengpeng Qu1, Qingsong Pang2
1Department of Gynecologic Oncology, Tianjin Central Hospital of Gynecology and Obstetrics, Affiliated Hospital of Nankai University, Tianjin 300100, People's Republic of China.
Introduction:
This study aims to measure the air-kerma rate of 192-Ir-HDR-afterloading source with an ionization chamber in air and a solid cylindrical phantom separately and to compare the dose calibration by the American Association of Physicists in Medicine (AAPM) Task Group TG-43U1 formalism with the Abacus treatment planning system (TPS).
Materials And Methods:
The air-kerma rate of 192Ir source was measured by an ionization chamber in air and a solid cylindrical phantom separately. For the interesting point position P (8cm, 90°), the values of the dose were calculated with the TG-43U1 formula and compared with data from the Abacus TPS with single and multiple dwell positions, respectively.
Results:
The air-kerma rate percentage deviations between the detector measurements in air and the source certificate were -1.28%, -0.91%, -0.71%, and 0.33% at the distances of 25cm, 50cm, 75cm, and 100cm, respectively. For the measurement in solid cylindrical phantom, the percent deviation from the air-kerma rate certificate was 1.85%. The percentage deviations of the dose calibration between Abacus TPS and TG-43U1 formalism at P (8cm, 90°) were -2.30%, 1.76%, and 2.10% with different distances (between the dwell positions) of 0cm, 0.5cm, and 1cm, respectively.
Conclusion:
The in-air technique was a new attempt for clinic routine measurement. Further studies are still necessary. As a treatment planning system, the Abacus TPS should apply the AAPM TG-43U1 formulism for the development required in the future.
