Introduction: To meet unique demands and stretch budgets, simulations will often be made rather than purchased. Although 3-dimensional printing can be useful, there are significant physical limitations of these materials. This project is intended to begin examining the physical properties of materials used in casting/molding that may be useful for simulant soft tissue creation.
Methods: A variety of materials (foams and rubbers, urethanes and silicones, ballistic and food grade gels) were cast in standardized forms for analysis and visualized via computed tomography scanner and ultrasound (US). Each sample was also tested using 18ga and 22ga needles to determine force required for penetration.
Results: Silicone rubbers were generally well visualized via US, with computed tomography imaging showing between 100 and 200 Hounsfield units. Ballistic and food grade gels measured in the areas of -175 and 8 Hounsfield units, respectively, while being clear under US. Foams, particularly the urethane, demonstrated low Hounsfield units and were essentially opaque to US because of air cell artifact. Needle force requirements ranged from 0.05 to 23.34 N. Gels and foams were in the lower range, but there was overlap with the silicone. The use of additives in the silicones allowed for a wide range of needle forces and tactile experiences.
Conclusions: Silicone and urethane materials can mimic soft tissues, for both imaging and interventions. Although there is significant potential for independent production of custom, high-fidelity simulants, further work is required to identify preferable combinations of materials and optimal techniques for their use.