Measurement of Temperature Distribution in Phantom Body by an Ultrasonic CT Method

自从热疗出现在癌症的治疗中以来，测量体内温度就变得越来越重要。在这种治疗中，重要的是将肿瘤的温度保持在42.5ﾟ℃以上，以避免对正常组织的热损伤。提出了一种间接测量人体任意横截面内部温度分布并显示图像进行监测的技术。本文研究了一种超声CT(计算机层析成像)方法，该方法通过一系列相对于人体不同方位的声音投影来间接测量人体内部的温度分布。超声CT主要是像X-射线CT一样获得人体横断面图像的方法之一，但它没有X-射线CT那样的辐射损伤，具有仪器简单的优点，利用…测量声波到达时间可以得到物体内部的声速分布更多的超声CT。本研究的目的是发展一种利用加热和非加热时声速的差异间接测量物体内部温度分布的方法。首先，我们比较了三种重建算法，以最小化所需的投影数目。接下来，我们对水中温度与声速的关系进行了实验，得到了水中温度与声速之间的关系。然后，将琼脂制成的体模放入水浴中，当一对超声波探测器平移和旋转时，测量一系列声音投影。用加热时的声分布减去非加热时的声分布，可以得到体模内的温度分布，精度为0.1ﾟc。血液、肌肉、脏器等水组织的结构差异不会影响温度分布的测量，因为加热时的声速减去了非加热时的声速，从而不影响温度分布的测量。最后，我们进行了横截面上有一块骨头横跨超声测量的实验。当骨骼或气体在测量区域时，投影包括数据缺失部分。实验结果表明，对投影进行修正可以得到近似的重建图像，如果缺失部分较小，还可以得到重建图像的温度分布。但是，如果漏掉的部分很大，我们就不能精确地计算出温度分布。较少

It has been getting importance to measure the interior temperature in the body since hyperthermia appeared in treatment of cancer. In this treatment, it is important to hold the temperature of tumor over 42.5ﾟc to avoid the heat damage of normal tissue. We anticipate a technology measuring indirectly the interior temperature distribution of the arbitrary transverse section in the body and displying the image for monitoring.In this paper, An ultrasonic CT (Computed tomography) method is researched for measuring indirectly the interior temperature distribution from a series of sound projections that are taken at several different orientations relative to a phantom body. Ultrasonic CT is mainly one of the methods getting the transverse image of the body as the same as X-ray CT.But it has the advantage of simpler instrument because it doesn't have the radiation injury like X-ray CT.We can obtain the sound speed distribution within the object by measuring the arrival time of sound wave with … More ultrasonic CT.The purpose of this study is to develop the method measuring indirectly the interior temperature distribution of an object from the difference of sound speed between heating and non-heating, using the characteristics the sound speed depends on the temperature.First, we compare three reconstruction algorithms to minimize a number of required projections. Next, we make an experiment about the dependence of temperature on sound speed in water and get a relation between the temperature and the sound speed in water. Then, phantoms made of agar are placed in a water bath, and a series of sound projections is measured when a pair of ultrasonic detectors are both translated and rotated. We can obtain the temperature distribution in phantom with accuracy 0.1ﾟc by subtracting the sound distribution when non-heating from one when heating. The structure differences of watery tissue like blood, musculature, and the viscera do not effect on the measurement of the temperature distribution, because it is deleted by subtracting the sound speed when non-heating from the sound speed when heating.Lastly, We make an experiment in which there is a bone crossing the transverse section of the ultrasonic measurement. When bone or gas is in the area of measurement, the projections include a data missing part. As a result of the experiment, we could obtain approximately the reconstructed image by the modification of the projections, and the temperature distribution, too, if the missing part is small. But we can not calculate precisely the temperature distribution, if the missing part is large. Less