Temperature Dependence of Thermal Properties of Ex Vivo Porcine Heart and Lung in Hyperthermia and Ablative Temperature Ranges

This work proposes the characterization of the temperature dependence of the thermal properties of heart and lung tissues from room temperature up to > 90 degrees C. The thermal diffusivity (alpha), thermal conductivity (k), and volumetric heat capacity (C-v) of ex vivo porcine hearts and deflated lungs were measured with a dual-needle sensor technique. alpha and k associated with heart tissue remained almost constant until similar to 70 and similar to 80 degrees C, accordingly. Above similar to 80 degrees C, a more substantial variation in these thermal properties was registered: at 94 degrees C, alpha and k respectively experienced a 2.3- and 1.5- fold increase compared to their nominal values, showing average values of 0.346 mm(2)/s and 0.828 W/(m center dot K), accordingly. Conversely, C-v was almost constant until 55 degrees C and decreased afterward (e.g., C-v = 2.42 MJ/(m(3)center dot K) at 94 degrees C). Concerning the lung tissue, both its alpha and k were characterized by an exponential increase with temperature, showing a marked increment at supraphysiological and ablative temperatures (at 91 degrees C, alpha and k were equal to 2.120 mm(2)/s and 2.721 W/(m center dot K), respectively, i.e., 13.7- and 13.1-fold higher compared to their baseline values). Regression analysis was performed to attain the best-fit curves interpolating the measured data, thus providing models of the temperature dependence of the investigated properties. These models can be useful for increasing the accuracy of simulation-based preplanning frameworks of interventional thermal procedures, and the realization of tissue-mimicking materials.

Automated summary

This study characterizes the temperature dependence of thermal properties of heart and lung tissues, focusing on ex vivo porcine hearts and deflated lungs. The thermal diffusivity, thermal conductivity, and volumetric heat capacity of these tissues were measured and analyzed. The results showed that the thermal properties of heart tissue remained nearly constant until around 80 degrees C, while a more significant variation was observed above that temperature. For lung tissue, there was an exponential increase in the thermal diffusivity and thermal conductivity with temperature, especially at supraphysiological and ablative temperatures. Regression analysis was used to develop temperature-dependent models for these properties, which can be useful for simulation-based preplanning of thermal procedures and tissue-mimicking materials.