Comparisons of various water-equivalent materials with water phantom using the Geant4/GATE simulation program

The aim of this study was to compare the dosimetric properties of various water- equivalent phantom materials, such as solid water WT1 (WT1), solid water RMI457 (RMI457), plastic water, virtual water, polymethyl methacrylate (PMMA), polystyrene and A150, with water phantom.

Percentage depth dose values were obtained with IBA Blue Phantom2 and solid water phantom (RW3) used in clinical radiotherapy. The measurements were carried out at 6 and 18 MV photon energies with a field size of 10 x 10 cm2 and source-skin distance (SSD) at 100 cm. Simulations for the commercial solid phantoms were performed under these same conditions using Geant4 Application for Tomographic Emission (Geant4/GATE) simulation code.

PMMA (3.66±1.43) % and A150 (2.40±2.20)% phantom materials were determined to have a low rate of water equivalence at 6 MV photon energy while WT1 (-2.80±2.17)% and plastic water (-2.04±2.13)% phantom materials showed a low rate of water equivalence at 18 MV photon energy. Solid water WT1 (0.13±1.11)% and RMI457 (-0.29±0.91)% phantom materials were seen to be good water-equivalent materials at 6 MV photon energy, while PMMA (-0.08±1.39)% and A150 (-1.08±1.53)% were the closest equivalent materials to  water at 18 MV photon energy.

All the materials examined in this study were found to be suitable for the daily dosimetric measurements in clinical applications. The most appropriate choice would seem to be to use water phantom for the dosimetric measurements in radiotherapy clinics depending on the possibilities and time.