Feasibility study of using polyacrylamide gel dosimeter as brain equivalent material in therapeutic energy range of X-rays

In this paper the feasibility study of using polyacrylamide gels as a brain equivalent material has been performed. Thus, the parameters of mass energy absorption coefficient (μ_en/ρ), mass stopping power (S/ρ), effective atomic number ($Z_{eff}$), mass attenuation coefficient (μ_eff/ρ) and absorbed dose delivered to polyacrylamide gel ($D$) were determined for this gel using analytical and Monte Carlo methods and were compared with brain reference material. The calculation results reveal that the relative difference between the calculated μ_en/ρ, S/ρ, $Z_{eff}$, μ_eff/ρ and $D$ for polyacrylamide gel and those for brain are 1.32%, less than 1%, less than 2%, less than 4% and less than 1%, respectively in therapeutic energy range. Consequently, like water, polyacrylamide gel can be also used for designing and construction of head and neck phantoms applied for validation of medical algorithms used in treatment planning systems. The advantage of using polyacrylamide gel as a brain equivalent material in comparison to water is that this gel is a reliable X and gamma rays dosimeter applicable for three dimensional dose distribution determination. Also, other advantages of this gel are its low price, availability and forming it in different sizes and shapes. These properties of the polyacrylamide gel make it beneficial as brain equivalent material in designing and construction of head and neck phantoms.