Measurement of thermal properties of biological tissues and tissue-mimicking phantom with a dual-needle sensor

This work presents the measurement of the thermal properties of ex vivo biological tissues (i.e., porcine liver and kidney tissues) as a function of temperature, along with the thermal characterization of a tissue-mimicking agar-based phantom. The evaluation of the thermal properties was performed by the dual needle technique, adopting a sensor equipped with two needles, capable to deliver thermal energy to the biomaterial and monitor the related tissue thermal behavior. Measurements of thermal conductivity, thermal diffusivity, and volumetric heat capacity were conducted at room temperature and at temperatures relevant from a biological point of view, namely, body temperature and temperatures of
$\boldsymbol{\sim 60\ ^{\circ}\mathrm{C}-65\ ^{\circ}\mathrm{C}}$
, which are typically correlated to instantaneous thermal damage in tissue. Thermal properties of biological tissue remained rather constant at the investigated temperatures: average values of thermal conductivity ranged from 0.515 W/(m·K) to 0.575 W/(m·K), thermal diffusivity ranged from 0.144 mm
²
/s to 0.163 mm
²
/s, whilst the average volumetric heat capacity was from 3.48 MJ/(m
³
·K) to 3.72 MJ/(m
³
·K). Furthermore, the thermal properties of the realized agar phantom were comparable to the ones of biological tissues. The results of this study provide valuable information for the characterization of porcine liver and kidney tissues, in terms of their thermal properties, to be used in predictive mathematical models of thermal therapies and validate the usage of agar phantoms as tissue-mimicking materials.