Non-invasive measurement of thermal conductivity and thermal diffusivity of Rat liver

生物材料的热物理性质通常通过使用插入活组织中的热探针来测量。由于机械创伤会在探针周围形成一滩血液和其他液体，这将显著改变结果，因此对于活组织，最好采用非侵入性技术。为了发展一种测量生物材料热导率和热扩散率的新技术，并将其应用于大鼠肝脏，利用红外测温仪测量了CO_2激光加热后样品表面的温度历程。导热系数和热扩散率的测定数据与瞬态热传导的理论分析相同的情况下，从比较。该方法的一个重要特点是不考虑对流和辐射传热对温度历程的影响，并以丙烯酸树脂为例验证了该方法的有效性，实验结果与参考值吻合较好。然后将本技术应用于大鼠肝脏。在麻醉下对SD大鼠进行腹部手术，并在体测量肝脏的热物理性质。对CO_2激光器，在吸收系数一定的情况下，得到了适当的数据，但测量数据在很大程度上取决于吸收系数。虽然因此需要更多的研究来解决这个问题，但已证实，本技术可用于澄清血液流动对热物理性质的影响。

Thermophysical properties of biological materials are usually measured by using a thermal probe that is inserted into living tissues. Since a pool of blood and other fluids lay form around the probe because of mechanical trauma and it will significantly alter the result, a non-invasive technique is preferable for living tissues. The objective of this research was to develop a new technique to measure the thermal conductivity and the thermal diffusivity of biological materials, and to apply it to the rat liver.The temperature history of the specimen surface that was heated by a C0_2 laser was measured by an infrared thermometer. Both the thermal conductivity and the thermal diffusivity were determined from comparison of measured data with theoretical analysis of transient heat conduction for the same situation. One of the important points in the present technique was to exclude the effect of convection and radiation heat transfer on the temperature history.An acrylic resin block was chosen to check the validity of the present technique, and it was confirmed that the measured data agreed well with reference values. Then the present technique was applied to a rat liver. A SD rat was abdominally operated under anesthesia and the thermophysical properties of liver were measured in vivo. Appropriate data were obtained for a given value of absorption coefficient for the C0_2 laser, but the measured data depended largely on the absorption coefficient. Although more study is therefore needed to solve this problem, it was confirmed that the present technique was useful to clarify the effect of blood flow on the thermophysical properties.