Analysis of X-ray beam parameters used to implement reference radiations for calibrating dosimetric systems for diagnostic radiology

Ionizing radiation metrology is the base to achieve reliable dose measurements in all areas; it is also part of the framework of a radiological protection program that requires the use of reliable instruments that comply with standard performance criteria worldwide accepted. The International Electrotechnical Commission (IEC) established the X-ray reference radiations that are recommended to be used for calibrating dosimetric systems for diagnostic dosimetry. In this work, X-ray beam qualities were implemented in the Dosimeter Calibration Laboratory of the Development Centre of Nuclear Technology; the characteristics of the beams were analyzed through the measurement of parameters like inherent tube filtration, beam uniformity; beam field size, energy spectra and peak voltage. The influence of using 99.425% and 99.999% purity filters was also investigated. The first half-value layers and the homogeneity coefficients were measured for the three RQR2, RQR6 and RQR10 IEC beam qualities. An ionization chamber was also calibrated against a standard chamber in all implemented reference radiations and the relevant sources of uncertainties were estimated. Beam parameters were adjusted to comply with IEC standard; the main source of uncertainty during the calibration process was due to the ionization chamber positioning set-up and the purity of the filters did not cause relevant influence on the beam energy spectra. (author)