Material selection for a 3D-printed tissue-equivalent cost-effective phantom for radiotherapy quality assurance

Abstract Background and Aims: Patient-specific 3D-printed phantoms are increasingly used for radiotherapy quality assurance (QA) because they are cost-effective and reproduce individual patient anatomy. A major challenge is identifying materials that mimic human tissue.In this work we systematically evaluate radiological properties of various commonly available and industrial 3D printing materials, whereby we include a combined characterization at diagnostic (keV) and therapeutic (MeV) photon energies. Methods and Materials: Over 60 cubes of plastic samples of about 30 materials and different in-fill densities were printed using three different filament printers. CT scans were acquired and the average Hounsfield Units (HU) for each sample was determined. Massdensities (ρm), electron density (ρe), and relative electron density (RED) were assessed. All samples were compared with ICRU reference data. The response at therapeutic energies was evaluated by irradiating the samples and measuring the deposited dose using a micro-diamond detector. These were compared with Pinnacle TPS predictions.