HIGH ACCURACY 3-DIMENSIONAL INVERSE ESTIMATION OF TEMPERATURE DISTRIBUTION IN A HUMAN BODY FOR ESTABLISHMENT OF HYPERTHERMIA TREATMENT

在本研究计画中，提出一种非侵入性的热疗下人体温度分布的逆数值估计方法。该方法利用多幅时间序列的单光子发射计算机断层扫描（SPECT）图像来估计每个组织的血流速度，取得了如下研究成果：（1）提出了一种同时估计每个组织的血流速度、血流速度的温度依赖性以及在治疗过程中被加热区域的温度分布的算法。采用有限元法计算了温度场分布。(2)该算法进行了测试与四层肌肉脂肪动态体模模型的温度估计程序。计算结果表明，该方法可以将温度分布估计到± 0.2 ℃以内。(3)我们的方法被应用到人体大脑的温度估计是基于X-CT图像建模。从这些结果可以看出，人体横截面上的温度分布可以估计到± 0.5 ℃以内。(4)该方法也被应用于恶性胶质瘤患者的治疗计划。结果表明，该方法可用于设计安全有效的热疗方案，并可用于热疗后的疗效检验。

In this research project, an inverse numerical estimation method of temperature distribution in a human body non-invasively under the hyperthermia treatment is proposed. In this method, the blood flow rate of each tissue is evaluated from several time sequential single photon emission computed tomography(SPECT) images of a subject under the treatment.The results obtained in our project are summarized as follows :(1) An algorithm to estimate the blood flow rates of every tissues of the subject, its temperature dependence and temperature distribution through a heated region of the subject under the treatment simultaneously is proposed. A finite element method (FEM) was used to calculate the temperature distribution.(2) The algorithm was tested with the four-layered muscle-fat dynamic phantom model by the developed temperature estimation program. The results show that the temperature distribution can be estimated to within ± 0.2 ℃.(3) Our method was applied to the temperature estimation of a human brain which is modeled based on X-CT images. From these results, it is shown that the temperature distribution over a cross-sectional area of a human body can be estimated to within ± 0.5 ℃.(4) The method was also applied to a treatment planning for patients with malignant glioma. Optimal positions of needle type applicators and the number of applicators could easily be determined in all cases.From these results, it is confirmed that the proposed method is applicable to plan effective and safety hyperthermia treatment, and also to check the effectiveness of the treatment after heating.