Achim Krauss and Ralf-Peter Kapsch 2007 Phys. Med. Biol. 52 6243 doi:10.1088/0031-9155/52/20/011
Achim Krauss and Ralf-Peter Kapsch
Show affiliationsThe relative uncertainty of the ionometric determination of the absorbed dose to water, Dw, in the reference dosimetry of high-energy photon beams is in the order of 1.5% and is dominated by the uncertainty of the calculated chamber- and energy-dependent correction factors kQ. In the present investigation, kQ values were determined experimentally in 5 cm × 5 cm and 10 cm × 10 cm radiotherapy beams of 8 MV and 16 MV bremsstrahlung by means of a water calorimeter operated at 4 °C. Ionization chambers of the types NE 2561 and NE 2571 were calibrated directly in the water phantom of the calorimeter. The measurements were carried out at the linear accelerator of the Physikalisch-Technische Bundesanstalt. It is shown that the kQ factor of a single ionization chamber can be measured with a standard uncertainty of less than 0.3%. No significant variations of kQ were found for the different lateral sizes of the radiation fields used in this investigation.
Issue 20 (21 October 2007)
Received 31 July 2007, in final form 22 August 2007
Published 1 October 2007
An Erratum for this article has been published in 2008 Phys. Med. Biol. 53 1151
Achim Krauss and Ralf-Peter Kapsch 2007 Phys. Med. Biol. 52 6243
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