Newman W H, Lele P P
J Biomech Eng. 1985 Aug;107(3):219-27. doi: 10.1115/1.3138546.
Knowledge of tissue thermal transport properties is imperative for any therapeutic medical tool which employs the localized application of heat to perfused biological tissue. In this study, several techniques are proposed to measure local tissue thermal diffusion by heating with a focused ultrasound field. Transient as well as near steady-state heat inputs are discussed and examined for their suitability as a measurement technique for either tissue thermal diffusivity or perfusion rate. It is shown that steady-state methods are better suited for the measurement of perfusion; however the uncertainty in the perfusion measurement is directly related to knowledge of the tissue's intrinsic thermal diffusivity. Results are presented for a transient thermal pulse technique for the measurement of the thermal diffusivity of perfused and nonperfused tissues, in vitro and in vivo. Measurements conducted in plexiglas, animal muscle, kidney and brain concur with tabulated values and show a scatter from 5-15 percent from the mean; measurements made in perfused muscle and brain compare well with the nonperfused values. An estimate of the error introduced by the effect of perfusion shows that except for highly perfused kidney tissue the effect of perfusion is less than the experimental scatter. This validation of the tissue heat transfer model will allow its eventual extension to the simultaneous measurement of local tissue thermal diffusivity and perfusion.
对于任何采用向灌注生物组织局部施加热量的治疗性医疗工具而言，了解组织热传递特性至关重要。在本研究中，提出了几种通过聚焦超声场加热来测量局部组织热扩散的技术。讨论并检验了瞬态以及近稳态热输入作为组织热扩散率或灌注率测量技术的适用性。结果表明，稳态方法更适合测量灌注；然而，灌注测量中的不确定性与组织固有热扩散率的知识直接相关。给出了用于测量灌注和未灌注组织体外和体内热扩散率的瞬态热脉冲技术的结果。在有机玻璃、动物肌肉、肾脏和大脑中进行的测量与表格值一致，并且显示出与平均值有5% - 15%的偏差；在灌注肌肉和大脑中进行的测量与未灌注值比较良好。对灌注效应引入的误差估计表明，除了高度灌注的肾脏组织外，灌注效应小于实验偏差。对组织传热模型的这种验证将使其最终能够扩展到同时测量局部组织热扩散率和灌注。
