伊藤 貴司¹, 崔 宗秀¹, 河西 千廣¹, 栗田 克己², 中島 真人², 油田 信一³

Takashi ITOH¹, Jong-soo CHOI¹, Chihiro KASAI¹, Katsumi KURITA², Masato NAKAJIMA², Shin-ichi YUTA³

¹アロカ株式会社, ²慶応義塾大学理工学部, ³筑波大学電子情報工学系

¹Aloka Co., Ltd., ²Faculty of Science and Technology, Keio Univ., ³Institute of Information Sciences and Electronics, University of Tsukuba

キーワード : computed tomography, ultrasonic imaging, degradation, refraction, reflection

Image degradations on ultrasonic CT (Computed Tomography) were evaluated by experiment using agar gel phantoms and by computer simulation. The phantoms were made by mixing agar gel with graphite powder and saccharose which mainly control attenuation and velocity respectively. The experimental results showed that the attenuation constants at the centers of the phantoms are always underestimated and that the errors depend on the velocity difference between the media and not on their actual attenuation constants. From computer simulation, it was determined that the attenuation errors are due to refraction of ultrasound and that they can be reduced by measuring the maximum values in the received intensity distributions. Although this correction method is not completely accurate as reflection is not considered, it was proved to be practical from the results of experiments and computer simulation.