The skin temperature distribution of a healthy human body exhibits a contralateral symmetry. Some lesions of facial nerve function are associated with an alteration of the thermal distribution of the human body. Since the dissipation of heat through the skin occurs for the most part in the form of infrared radiation, infrared thermography is the method of choice to capture the alteration of the infrared thermal distribution. This paper presents a new method of analysis of the thermal asymmetry named effective thermal area ratio, which is a product of two variables. The first variable is mean temperature difference between the specific facial region and its contralateral region. The second variable is a ratio, which is equal to the area of the abnormal region divided by the total area Using this new method, we performed a controlled trial to assess the facial nerve function of the healthy subjects and the patients with Bell's palsy respectively. The results show: that the mean specificity and sensitivity of this method are 0. 90 and 0. 87 respectively, improved by 7% and 26% compared with conventional methods. Spearman correlation coefficient between effective thermal area ratio and the degree of facial nerve function is an average of 0. 664. Hence, concerning the diagnosis and assessment of facial nerve function, infrared thermography is a powerful tool; while the effective thermal area ratio is an efficient clinical indicator.%健康人体的温度分布存在一种双侧对称性,当面神经功能受损时,将改变这种热分布的对称性.人体热量大多通过红外辐射的形式散发,因此利用红外热成像技术可以有效捕捉这种红外热辐射分布的改变.本文提出一种新的热不对称分析的方法——有效热面积比,即计算面部特定区域与对侧区域的温差乘以温度异常区面积与总面积之比.利用这种方法对面神经功能损伤的患者和健康人群作对照性试验,结果显示:此方法的特异性和敏感性平均为0.90和0.87,比常规方法提高了7％和26％,有效热面积比与面神经功能的损伤程度正相关,平均为0.664.因此,关于诊断和评估面神经功能,红外热成像是一种有力的工具,有效热面积比是一项高效的临床指标.
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