Measurement of some dosimetric parameters for two mammography systems using thermoluminescent dosimetry

Abstract

Abstract The Backscatter Factors (BSF), Entrance-Surface Dose (ESD) and Relative Depth Dose (RDD) were assessed by Thermoluminescent Dosimetry (TLD) technique. The measurements have been made varying the geometric and spectral conditions, corresponding to the most radiographic techniques employed in conventional and computer mammographic procedures, i.e., beam qualities in the range of 0.35–0.43 mmAl, tube voltages from 25 kV to 32 kV, anode/filter combinations (Mo/Mo, Mo/Rh and Rh/Rh), different focus-image detector distances from 56 cm to 66 cm, area of irradiation (81, 157, 234 and 432 cm2) and thickness of the phantom. Results indicate that BSF values show a slight dependence on the various parameters considered, except with the variation of the focus-film distance, where found that this parameter does not have influence on the BSF. ESD values show a strong dependence on the various parameters considered, showing substantially lower values (40%) for computer mammography. RDD curves decrease nearly exponentially with the depth and depend strongly on the spectral conditions. The obtained values show a satisfactory agreement with other studies obtained through Monte Carlo simulation, ionization chambers and thermoluminescent dosimeters.