Measurement of the Linear Attenuation Coefficient of Resin-Based Water-Equivalent Materials

Phantoms are devices that represent the human body both in shape and composition. Phantoms materials are designed to simulate different human tissues such as bone, lung, soft tissue, muscle and others]. Liquid water is also a widely simulated material because water comprehends a significant fraction of the human body. To represent human tissues, phantom materials must simulate its physical and radiological properties. Mass density 𝜌 and effective atomic number 𝑍_𝑒𝑓𝑓 can describe the physical quantities, but radiological characterization requires knowledge of the attenuation properties because such properties are highly dependent on energy. Radiological properties can be well-represented by the linear attenuation coefficient 𝜇(𝐸). In recent publications, measurements of the linear attenuation coefficients were done for characterization of breast tissues and bone tissue substitutes. In order to characterize water-substitute materials, four resin-based water-equivalent samples developed by a mathematical algorithm were analysed and had their linear attenuation coefficient determined within the energy range from 10 to 150 keV. A poly-energetic narrow beam was adopted using a tungsten-target x-ray tube (model MG 450, Philips Medical Systems, 3000 Minuteman Road, Andover, MA) attached to a constant-potential generator. The tube was operated at constant-potential of 150 kV and had a cylindrical collimator with internal diameter of 1.5 mm placed 14 cm from the x-ray tube focal spot. An additional filtration of 4.6 mm of aluminium was also used after the collimator.