Determination of water equivalent ratio for some dosimetric materials in proton therapy using MNCPX simulation tool

The water equivalent ratio (WER) was calculated for polypropylene (PP), paraffin, polyethylene (PE), polystyrene (PS), polymethyl methacrylate (PMMA), and polycarbonate materials with potential applications in dosimetry and medical physics. This was performed using the Monte Carlo simulation code, MCNPX, at different proton energies. The calculated WER values were compared with National Institute of Standards and Technology (NIST) data, available experimental and analytical results, as well as the FLUKA, SRIM, and SEICS codes. PP and PMMA were associated with the minimum and maximum WER values, respectively. Good agreement was observed between the MCNPX and NIST data. The biggest difference was 0.71% for PS at 150 MeV proton energy. In addition, a relatively large positive correlation between the WER values and the electron density of the dosimetric materials was observed. Finally, it was noted that PE presented the most analogous Depth Dose Characteristics to liquid water.