In-Vivo Measurement of Thermal Diffusivity of Living Subcutaneous Tissue

在1991学年，首先从理论上考察了测量原理及其精度，然后对已知热物理性质与生物组织和器官相似的固体材料进行了热导率和扩散率的测量。通过这些测量，澄清了该方法存在的问题。在1992学年，对固体中的三维温度分布进行了数值模拟，提出了一些新的方法，并对其在各向异性材料中的精度和适用性进行了检验。此外，还进行了测量，以获得臂和手背皮下组织的导热性和扩散率。本项目的主要成果如下：1。在局部加热、表面对流和辐射热损失的边界条件下，对二维对称热传导方程进行了数值求解。当用加热区域的平均净热流密度来定义无量纲温度时，可以得到与这些热损失无关的无量纲温度与傅里叶数之间的唯一关系。该关系式可用于同时计算导热系数和扩散系数。结果表明，当热流密度和加热半径的估计误差分别在5%和3%以内时，该方法可以在10%以内得到非金属固体的导热系数和扩散系数。利用丙烯和氯乙烯板等材料的测量结果，准确地估算了激光功率的反射率。对热流密度进行校正后，导热系数和扩散系数的误差可进一步减小到2-5%。对三维生物传热方程进行了数值分析。阐明了各向异性特性、灌注和代谢率对表面温度分布的影响。为了提高测量精度，并将该方法应用于各向异性材料，采用了受热表面温度-时间响应的多点值，并提出了一些新的扩展方法。这些方法的可用性已经过审查。记录了正常和止血条件下手臂和手背受热表面的温度-时间反应。灌注和代谢率对皮下组织热导率和扩散率的影响目前已在上述新方法的基础上进行了研究。少

In the academic year 1991, the principle of the measurement and its accuracy had been examined theoretically at first, then the thermal conductivity and diffusivity were measured for the solid materials with known thermophysical properties similar to those biological tissues and organs. From these measurements, the problems existing in the method had been clarified. In the academic year 1992, three dimensional temperature distributions in a solid were obtained numerically, then some new methods were proposed and their accuracy and applicability for the anisotropic materials were examined. Further, the measurements had been done to obtain thermal conductivity and diffusivity of the subcutaneous tissues of the brachium and the back of the hand. The main achievements of the project are concluded as follows:1. Two-dimensional symmetric heat conduction equation was solved numerically under the boundary conditions of local heating, and convection and radiation heat losses on the surface. Whe … More n the non-dimensional temperature is defined by using the average net heat flux over the heating area, an unique relation between the non-dimensional temperature and Fourier number can be obtained which is independent of these heat losses. This relation can be used to evaluate the thermal conductivity and diffusivity simultaneously.2. It is found that the present method could obtain the thermal conductivity and diffusivity of non-metal solids within an error of 10%, when the errors of heat flux and heating radius are estimated within 5% and 3%, respectively. With the help of measured results of such materials as Acryl and Chloride Vinyl plates, the reflective fraction of laser power has been estimated accurately. When the heat flux is corrected, the errors of thermal conductivity and diffusivity can be further reduced to 2-5%.3. Three-dimensional bioheat transfer equation was analyzed numerically. The effects of the anisotropic characteristic, perfusion and metabolic rate on the surface temperature distributions have been clarified.4. To improve the accuracy of measurement and to apply the method for anisotropic materials, multi-points values of the temperature-time response of the heated surface were used, and some new expanded methods have been proposed. The availability of these methods have been examined.5. The temperature-time responses of the heated surfaces of the brachium and the back of the hand have been recorded under both normal and hemostasis conditions. The effects of the perfusion and metabolic rate on thermal conductivity and diffusivity of subcutaneous tissues have now been examining based on the above new methods. Less