Characterization of the urethane based tissue equivalent substitute for phantom construction: model molding, XCOM and MCNPX studies

Abstract

The Soft and Lung tissue equivalent substitute (STES and LTES) were developed from urethane PMC121/30 Dry (A and B) of Smooth-On, USA. The part A and B were mixed in the ratio 1:1 and further mixed with calcium carbonate (CaCO3) at a ratio 2:1 by mass. Air moisture was extracted from the mixture for 10minutes. This is the STES and the density after air extraction was 1.04gcm-3. The LTES was developed by mixing the STES and polystyrene beads at a ratio 10:1 by mass. The density of the LTES was 0.25gcm-3 after air extraction. The STES and the LTES were subjected to compression test for stress-strain analysis. The elemental composition of STES and LTES was achieved using XCOM software with the IUPAC nomenclatures of the source compounds as inputs. The elemental composition obtained was used to modify the lung and the soft tissue material of the AMALE and AFEMALE computational phantom of ORNL. The phantom was subjected to photon exposure (0.06MeV-15.00MeV) using MCNPX Version 27e. The results from MCNPX provided the bremsstrahlung, positron annihilation, and the fluorescence energies that was used to estimate the g-factor. The mass-energy transfer coefficient (μtra/ρ) and the mass-energy absorption coefficient (μen/ρ) were calculated using the values of g-factor, the fluence and the Kerma. The μen/ρ of the tissue-equivalent agrees with the National Institute of Standard values and the ICRU 44. The STES and LTES are technically proper research and teaching models for dose measurements with these results.