Evaluation of the Half-Value Layer and the validity of Inverse-Square Law applied to radiology: Comparison among Deterministic Calculation, Monte Carlo Method and Experimental Results

This work provides a preliminary analysis of the influence of additional filtration composition on Half Value Layer (HVL) determination and the significance on using Inverse Square Law (ISL) in conventional radiology and mammography considering realistic geometry. It compares Deterministic Calculation (DC), Monte Carlo Method (MC) and Experimental Results (ER) in order to make the purposed analysis. Six different aluminum-alloys (1% impurity) commercialized around the world and pure Al were taken into account. In the experimental arrangement for conventional radiology, it was used a combination of Tungsten target and Al filtration for three different peak tensions (66 kVp, 81 kVp, 125 kVp). For HVL determination in mammography, it was used three different target-filtration combinations (Mo-Mo, Mo-Rh, W-Rh) for three different peak tensions (25 kVp, 30 kVp, 35 kVp). The spectra used for deterministic calculation was taken from Report No 78 of the Institute of Physics and Engineering in Medicine, 1997. Results presented show that the composition of Aluminum filters used to perform HVL test can influence significantly the HVL value and that ISL must be applied carefully to correct data for dosimetry in radiological applications.