Investigation of the aptness of newly developed epoxy-based equivalent tissues for newborn and 5-years old in paediatric radiology

The varied radiological applications of tissue equivalent (TE) materials encompass quality checks, diagnostic imaging and dose evaluations. Nevertheless, the availability of compounds representative of paediatric patient tissues for scientific use in lower diagnostic photon energy spectra is limited. In this study, several TE substitutes were developed which replicate the radiographic characteristics of human tissue within these energy ranges, i.e. TE materials for neonatal soft tissue (ESST-NB), neonatal skeletal tissue (ESTB-NB), and the equivalent tissue types representative of a 5 year old child (ESST and ESBT, respectively). The ORNL stylised computational model series was used as a source for the desired elemental proportions. The density, effective atomic number, CT numbers and electron densities calculated for the developed tissue substitutes approximated those of the phantom system used as a reference. Additionally, in keeping with the material choice and production limitations, as close correlations as possible were achieved for all the materials in relation to the reference data for mass densities, mass attenuation coefficients and mass energy-absorption coefficients. The TE substitutes for the newborn over an energy range of 47 keV to 66 keV exhibited maximum discrepancies for {\mu}/\r{ho} of 1.6% to -3.01%, and for {\mu}_en/\r{ho} of 1.15% to -1.4% in relation to the ORNL reference samples. The respective equivalent data ranges were 1.09 % to -3.02% and 1.92% to -2.53% for the TE materials representative of a 5-year-old. Given the excellent concordance achieved between the newly constructed TE materials and the reference data, these compounds can subsequently be utilised to create physical phantoms representative of tissue types in neonates and children aged 5 years.