Development of a permeable phantom for dynamic contrast enhanced (DCE) imaging quality assurance: material characterization and testing

The wide-spread use of contrast-enhanced imaging is often combined with pharmaco-kinetic modeling to estimate the level of perfusion and/or permeability of the tissue or tumour under investigation. Despite the availability of advanced experimental methods and phantoms to test the accuracy of blood flow and transfer rates, the reliable estimation of tissue permeability following kinetic modeling against a known truth is still outstanding. This work reports on the first two phases of the development of a tissue mimicking permeable hepatic perfusion phantom being tested under DCE-CT: material selection and fabrication, as well as property testing. The required properties of these synthetic materials include a tailored porous structure, tumor mimicking pore size and tumor mimicking permeability. Three phantom materials were investigated for their capabilities to address these requirements, i.e. polydimethylsiloxane (PDMS), thermoplastic polyurethane (TPU) and agar gel. Porous structures were made using different techniques such as phase separation micro-molding (for PDMS) and a particular leaching process (for PDMS and TPU). Manual pores were made on agar gel and all were characterized under SEM, micro-CT scan and pycnometer. TPU was selected as the phantom material of choice moving forward due to its high homogeneity in pore size ranging from 200 to 400 m, which mimics tumor vasculature the best. TPU also has the highest permeability of the three materials and its stable structure provides good repeatability.