小川 俊雄¹, 片倉 景義¹, 梅村 晋一郎¹, 児玉 真塩², 林 信成³, 玉木 長良³, 中島 言子³, 山本 和高³, 米倉 義晴³, 鳥塚 莞爾³

Toshio OGAWA¹, Kageyoshi KATAKURA¹, Shinichiro UMEMURA¹, Mashio KODAMA², Nobushige HAYASHI³, Nagara TAMAKI³, Kotoko NAKAJIMA³, Kazutaka YAMAMOTO³, Yoshiharu YONEKURA³, Kanji TORIZUKA³

¹日立中央研究所第9部, ²日立メディコ柏工場, ³京都大学医学部附属病院放射線核医学科

¹9th Department, Central Research Lab., Hitachi Ltd., ²Hitachi Medical Co.,Kashiwa, ³Department of Radiology and Nuclear Medicine, Kyoto University Hospital

キーワード : Ultrasonic scanner, IN VIVO measurement, Sound speed, Delay line, Synthetic aperture

　This paper describes a new method of IN-VIVO sound-speed measurement in the reflection mode. The mean sound speed between the reflector and the linear array transducer is measured using the following two parameters, time of flight and the distance between two receiver elements. To detect the time of flight, we adjust the delay line time compensator in the system to get the sharpest image of the reflector. The value of this compensated time corresponds to the sound speed in the medium.
　A new ultrasonic scanner employing a large modified-synthetic receiver aperture provides a high resolution image and high sound-speed measurement accuracy. This system also uses dynamic focusing in the time compensator, focusing in real time the ultrasonic beam at each reflector at each depth. Using this approach, the time required for this measurement is about 1 sec.
　System measurement error was less than 0.5% in water in the temperature range 5 to 40°C. For an IN VIVO measurement, we applied this method to a human liver, obtaining the mean sound speed between the diaphragm and the transducer. This method has potential application for detecting tissue abnormality in clinical use.