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Thermal ablative techniques have been used in kidney tumour treatments; these treatments use electromagnetic energy to increase the temperature of the target tissue in order to destroy it. Dielectric and thermal properties influence the deposition of electromagnetic energy and the heat distribution into the tissue, respectively. Accurate knowledge of dielectric and thermal properties permits accurate modelling of the therapeutic results. Extensive research has been conducted on dielectric property characterisation of tissue, while significantly less data are available in literature on thermal property characterisation. The aim of this study is to experimentally investigate the kidney thermal properties in ex vivo ovine models (n = 4) in a temperature range from room to ablative temperatures (95–96 °C). Results show changes in thermal properties at temperatures approaching the water transition to gas, i.e. above 95 °C.

Electromagnetic-based hyperthermic therapies induce a controlled increase of temperature in a specific tissue target in order to increase the tissue perfusion or metabolism, or even to induce cell necrosis. These therapies require accurate knowledge of dielectric and thermal properties to optimise treatment plans. While dielectric properties have been well investigated, only a few studies have been conducted with the aim of understanding the changes of thermal properties as a function of temperature, i.e., thermal conductivity, volumetric heat capacity and thermal diffusivity. In this study, we experimentally investigate the thermal properties of ex vivo ovine liver in the hyperthermic temperature range, from 25 &deg, C to 97 &deg, C. A significant increase in thermal properties is observed only above 90 &deg, C. An analytical model is developed to model the thermal properties as a function of temperature. Thermal properties are also investigated during the natural cooling of the heated tissue. A reversible phenomenon of the thermal properties is observed, during the cooling, thermal properties followed the same behaviour observed in the heating process. Additionally, tissue density and water content are evaluated at different temperatures. Density does not change with temperature, mass and volume losses change proportionally due to water vaporisation. A 30% water loss was observed above 90 &deg, C.

In electromagnetic hyperthermic applications, the thermal properties of the biological tissue under treatment, as well as its dielectric properties, influence the deposition of the electromagnetic energy and the heat distribution into the tissue. Thus, their knowledge can allow to accurately model the therapeutic results. The induced heat distribution and the consequent temperature increase rate are ruled by the thermal properties of the biological tissues. The aim of this work is to experimentally investigate the thermal properties of ex vivo liver, lung, kidney, muscle and bone marrow at room (N=66) and body (N=45) temperatures; and to correlate these properties with the density and water content of the tissue.