Thermophysical properties of swine myocardium

This paper presents the experimental technique and results for the thermal conductivity, thermal diffusivity, and density of swine myocardial tissue. These properties were measured for freshly excised tissue. Thermal properti es were measured using a self-heated thermistor probe, while the density wa s measured using a water displacement method. Thermistor probes were insert ed into the tissue of interest and were used to supply heat within the tiss ue as well as to monitor the temperature rise in the tissue. An empirical c alibration procedure was used to measure the properties of the tissue at di fferent temperatures. The measurement instrument was first calibrated again st agar-gelled water and glycerol at each temperature. The measurements wer e made at temperatures of 25, 37, 50, 62, and 76 degrees C. The uncertainty in the measurement ranges From 2% at lower temperatures to about 5% at hig her temperatures (T > 50 degrees C). The properties of the tissue depend si gnificantly on the water content. At temperatures higher than 50 degrees C, there is significant water loss from the tissue during the procedure. The water loss is found to vary exponentially with the increase in temperature relative to ambient. Consequently, there is a decrease in the thermal condu ctivity values with increasing temperature. This decrease, however, is not as much as one would expect From the water loss data. A hypothesis to expla in the relationships among water loss, cell damage, and thermal properties is proposed.