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
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.