Corss-calibration of ionization chambers in proton and carbon beams

The calibration coefficinets of a parallel plate ionization chamber are examined by comparing the coefficients obtained through three methods: a calculation from a Co-60 calibration coefficient, N[D,w,Co-60], a cross-calibration of a parallel plate ionization chamber using a cylindrical ionization chamber at the plateau region of a mono-energetic beam and a cross-calibration of the chamber using a cylindrical chamber at the middle of the SOBP of the therapeutic beams, This paper also examines reference conditions for determining absorbed dose to water in the cases of therapeutic carbon and proton beams, In the dose calibration procedure recommended by IAEA, irradiation fields should be larger than 10 cm in diameter and the water phantom should extend by at least 5 cm beyond each side of the field. These recommendations are experimentally verified for proton and carbon beams. For proton beams, the calibration coefficients obtained by these three methods epproximately agreed. For carbon beams, the calibration coefficients obtained by the second method were about 1.0 % larger thanthose obtained by the third method, and the calibration coefficinets obtained by cross-calibration using 290 MeV/u beams were 0.5% lower than those obtained using 400 MeV/u beams. The calibration coefficinet obtained by the first method agreed roughly with the results obtained by SOBP beams

Proton Beam Dosimetry Intercomparison

The Third Korea-Japan Joint Meeting on Medical Physics and The Second Asia Oceania Congress of Medical Physic

Feasibility study of glass dosimeter postal dosimetry audit of high-energy radiotherapy photon beams

INTRODUCTION: \nThe characteristics of a glass dosimeter were investigated for its potential use as a tool for postal dose audits. Reproducibility, energy dependence, field size and depth dependence were compared to those of a thermoluminescence dosimeter (TLD), which has been the major tool for postal dose audits worldwide.\nMATERIALS AND METHODS: \nA glass dosimeter, GD-302M (Asahi Techno Glass Co.) and a TLD, TLD-100 chip (Harshaw Co.) were irradiated with gamma-rays from a (60)Co unit and X-rays from a medical linear accelerator (4, 6, 10 and 20 MV).\nRESULTS: \nThe dosimetric characteristics of the glass dosimeter were almost equivalent to those of the TLD, in terms of utility for dosimetry under the reference condition, which is a 10 x 10 cm(2) field and 10 cm depth. Because of its reduced fading, compared to the TLD, and easy quality control with the ID number, the glass dosimeter proved to be a suitable tool for postal dose audits. Then, we conducted postal dose surveys of over 100 facilities and got good agreement, with a standard deviation of about 1.3%.\nCONCLUSIONS: \nBased on this study, postal dose audits throughout Japan will be carried out using a glass dosimeter

Proton Beam Dosimetry -Protocol and intercomparison in Japan

International Symposium on Standards and Codes of Practice in Medical Radiation Dosimetr