Radiological and physical properties of tissue equivalent mammography phantom: Characterization and analysis methods

Abstract

This article provides methods to fabricate and characterize tissue equivalent properties of mammography phantom. The characterized properties are elemental composition, effective atomic number, electron density, attenuation coefficient and CT number. Polyvinyl alcohol (PVAL), ethanol solution and graphite powder were used to develop samples of breast phantoms. First, the microstructure and elemental composition of the phantom materials were acquired from the field emission scanning electron microscopy (FESEM). FESEM micrography was a good analytical technique to indicate void spaces within the phantom. Next, the effective atomic number and electron density were calculated from the percentage of elemental composition based on the energy dispersive X-ray analysis (EDXA). Mayneord's formula and the Phy-X/ZeXTRa software were used to evaluate the effective atomic number. The calculations show that the effective atomic number ranged from 7.137 to 7.264 and 6.75–7.05 for Mayneord and Phy-X/ZeXTRa approach respectively. The electron density ranged from 3.191–3.209 × 1023/g. These values were found to be in good agreement with water and breast tissue by ICRP and AAPM standards. Then, the mass attenuation coefficients of the PVAL were calculated based on the transmission of low photons by using X-ray fluorescent (XRF) technique at 16.61–25.26 keV. The mass attenuation coefficient values were found to be close to water and breast tissue when results were compared to XCOM values. Finally, CT images were acquired to measure CT numbers, which were found to be near to CT number of breast tissues, −21.40 to 24.13 HU. Based on the ICRP, AAPM, BIRADS and XCOM standards, the study successfully showed methods to fabricate and characterized mammography phantoms.