[Dosimetry of HDR afterloading machines with Ir-192- und Co-60-sources: comparison of different international protocols].

The air kerma rate in air at a reference distance of 1 meter from the source is the recommended quantity for the specification of gamma ray source in brachytherapy. The absorbed dose for the patients is directly proportional to the air kerma rate. Therefore the air kerma rate should be determined before the first use of the source on patients by a medical physicist who is independent from the source manufacturer. The air kerma rate will then be applied in the calculation of the dose delivered to patients. In practice, high dose rate (HDR) Ir-192 afterloading machines are mostly used in brachytherapy treatment. Currently HDR-Co-60 increasingly come into operation, too. The essential advantage of the use of Co-60 sources is its longer half-life compared to Ir-192. In addition, the purchasing and disposal costs are lower. The use of HDR-Co-60- afterloading machines is also quite interesting for developing countries. This work describes the dosimetry at HDR afterloading machines according to the protocols DIN 6809-2 (1993) in relation to the DGMP-Report 13 (2006), IAEA-TECDOC-1274 (2002) and AAPM Report 41 (1993) with the nuclides Ir-192 and Co-60. We have used 3 different measurement methods (with a cylindrical chamber in solid phantom and in free air and with a well chamber) in dependence of each of the protocols. We have shown that the standard deviations of the measured air kerma rate for the Co-60 source are generally larger than those of the Ir-192 source. The measurements with the well chamber had the lowest deviation from the certificate value. In all protocols and methods the deviations stood for both nuclides by a maximum of about 1.2% for Ir-192 and 2.5% for Co-60-sources respectively.

Zakaria GA ，Schütte W ，Azhari HA 《Zeitschrift fur Medizinische Physik》

The IPEM code of practice for determination of the reference air kerma rate for HDR (192)Ir brachytherapy sources based on the NPL air kerma standard.

Bidmead AM ，Sander T ，Locks SM ，Lee CD ，Aird EG ，Nutbrown RF ，Flynn A ，IPEM Working Party ... -  《-》

Dosimetric verification of source strength for HDR afterloading units with Ir-192 and Co-60 photon sources: Comparison of three different international protocols.

Azhari HA ，Hensley F ，Schütte W ，Zakaria GA ... -  《-》

Comparison of 60cobalt and 192iridium sources in high dose rate afterloading brachytherapy.

Richter J ，Baier K ，Flentje M 《-》

Correction factors for source strength determination in HDR brachytherapy using the in-phantom method.

For the purpose of clinical source strength determination for HDR brachytherapy sources, the German society for Medical Physics (DGMP) recommends in their report 13 the usage of a solid state phantom (Krieger-phantom) with a thimble ionization chamber. In this work, the calibration chain for the determination of the reference air-kerma rate Ka,100 and reference dose rate to waterDw,1 by ionization chamber measurement in the Krieger-phantom was modeled via Monte Carlo simulations. These calculations were used to determine global correction factors k(tot), which allows a user to directly convert the reading of an ionization chamber calibrated in terms of absorbed dose to water, into the desired quantity Ka,100 or Dw,1. The factor k(tot) was determined for four available (192)Ir sources and one (60)Co source with three different thimble ionization chambers. Finally, ionization chamber measurements on three μSelectron V2 HDR sources within the Krieger-phantom were performed and Ka,100 was determined according to three different methods: 1) using a calibration factor in terms of absorbed dose to water with the global correction factor [Formula: see text] according DGMP 13 2) using a global correction factor calculated via Monte Carlo 3) using a direct reference air-kerma rate calibration factor determined by the national metrology institute PTB. The comparison of Monte Carlo based [Formula: see text] with those from DGMP 13 showed that the DGMP data were systematically smaller by about 2-2.5%. The experimentally determined [Formula: see text] , based on the direct Ka,100 calibration were also systematically smaller by about 1.5%. Despite of these systematical deviations, the agreement of the different methods was in almost all cases within the 1σ level of confidence of the interval of their respective uncertainties in a Gaussian distribution. The application of Monte Carlo based [Formula: see text] for the determination of Ka,100 for three μSelectron V2 sources revealed the smallest deviation to the manufacturer's source certificate. With the calculated [Formula: see text] for a (60)Co source, the user is now able to accurately determine Ka,100 of a HDR (60)Co source via in-phantom measurement. Moreover, using the presented global correction factor [Formula: see text] , the user is able to determine the future source specification quantity Dw,1 with the same in-phantom setup.

Ubrich F ，Wulff J ，Engenhart-Cabillic R ，Zink K ... -  《-》