|Budget Amount *help
¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1996 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1995 : ¥2,300,000 (Direct Cost : ¥2,300,000)
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
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