(387e) Poly(vinyl alcohol) Tissue Phantoms for Robust Modeling of in Vitro Thermal Transport

Careful control of thermal transport in tissue is critical for a variety of applications including thermal ablation, cancer hyperthermia, and most recently, medical implant infection control. The ability to study thermal transport in tissues with complex geometries has been hindered by the lack of appropriate tissue phantoms. Such a material must combine three critical features: its thermal properties must be tunable to match various tissue; it must be pourable to completely occupy the geometry of interest, enveloping delicate microprobes and conforming to complex shapes; and it must be shelf-stable over the duration of the experimental trials. Here, we report the development of a tissue phantom which combines these three attributes. In this work, poly(vinyl alcohol) (PVA) tissue phantoms were synthesized by carefully timed crosslinking of 8 wt% PVA solutions in water to produce temperature and volume stable hydrogels. The pure hydrogel matches the thermal properties (heat capacity and thermal conductivity) of water but can be tuned by addition of fillers with different thermal properties. Tissue phantom composites containing up to 40 wt% microparticles are demonstrated with tunable thermal properties while still retaining their chemical and swelling stability as well as their pourability. Silicon carbide and hydrophobic, poly(methyl methacrylate) resin were dispersed uniformly throughout the PVA gel to produce phantoms with decreased and increased thermal resistance, respectively. The heat capacity of all hydrogel composites was measured using differential scanning calorimetry. Thermal modeling was achieved by pouring the PVA solution, prior to crosslinking, over a temperature controlled, electrical resistive heating element with temperature probes imbedded throughout the mimic, laterally away from the heat source. Transient temperature measurements were obtained through the tissue phantom for temperature setpoints up to 80 °C.