Experimental and Monte Carlo-simulated spectra of standard mammography-quality beams

A spectrometric study of standard mammography-quality beams by using experimental and Monte Carlo simulation methods was carried out in this work. The qualities of these beams are described according to the International Electrotechical Commission 61267 standard and the Technical Report Series 457 International Atomic Energy Agency report. Specifically, the non-attenuated RQR-M beam series was studied.

A Si-PIN diode-based spectrometer and the PENELOPE Monte Carlo code (v. 2008F1) were used for experiments and simulations, respectively. In addition, an ionization chamber was used to determine the half-value layers (HVLs) of each beam quality. The measurements were done in the mammography dosimeter calibration setup of our laboratory, and the Monte Carlo simulations reproduced such conditions.

The relative differences between the HVLs calculated from experimental and simulated spectra were lower than 2.4% for all the beam qualities studied. These differences are 1.2% and 3.1% when comparing the HVLs calculated from the experimental and simulated spectra to those determined by using the ionization chamber, respectively. A semi-empirical relation was found to obtain the nominal tube potential from the effective tube potential.

According to our results, the mammography beams used in this work have energy spectra similar to clinical beams.