Water equivalence of polymer gel dosimeters

To evaluate the water equivalence and radiation transport properties of polymer gel dosimeters over the wide range of photon and electron energies 14 different types of polymer gels were considered. Their water equivalence was evaluated in terms of effective atomic number (ZeffZeff), electron density (ρeρe), photon mass attenuation coefficient (μ/ρμ/ρ), photon mass energy absorption coefficient (μen/ρμen/ρ) and total stopping power (S/ρ)tot(S/ρ)tot of electrons using the XCOM and the ESTAR database. The study showed that the effective atomic number of polymer gels were very close (<1%<1%) to that of water except PAGAT, MAGAT and NIPAM which had the variation of 3%, 2% and 3%, respectively. The value of μ/ρμ/ρ and μen/ρμen/ρ for all polymer gels were in close agreement (<1%<1%) with that of water beyond 80 keV. The value of (S/ρ)tot(S/ρ)tot of electrons in polymer gel dosimeters were within 1% agreement with that of water. From the study we conclude that at lower energy (<80keV) the polymer gel dosimeters cannot be considered water equivalent and study has to be carried out before using the polymer gel for clinical application.