山越 芳樹, 岡本 恭明

Yoshiki YAMAKOSHI, Takaaki OKAMOTO

群馬大学工学部

Gunma University, Faculty of Engineering

キーワード : Displacement, Doppler, Measurement accuracy

In order to measure the displacement of internal tissues using ultrasonic waves, several methods have been proposed and some are used in medical diagnosis. In these methods, a technique based on the ultrasonic Doppler method may be the most promising, because the internal movements can be measured with high accuracy. To detect the phase shift due to the ultrasonic Doppler effect, two different type of the method are known. The first method is based on the use of phase locked loop technique and the internal movements are measured by tracking, for example, zero cross points of the received ultrasonic waves. The second method is based on the use of a quadrature detector and the internal movements are calculated from the variation of the quadrature detector output signals. However in the latter method, it is also known that the measuring accuracy is decreased under proper conditions of the received signals. In this paper, the measuring accuracy of the internal displacement estimation based on the use of the quadrature detector is analyzed theoretically. Numerical experiments which were carried out in order to evaluate the estimation error quantitatively are shown.