A new method for measuring small local vibrations in the heart using ultrasound

In order to diagnose ventricular dysfunction based on the acoustic characteristics of the heart muscle of the ventricle, it is necessary to detect vibration signals from various parts of the ventricular wall. This is, however, difficult using previously proposed ultrasonic diagnostic methods or systems. The reason is that the amplitude of the cardiac motion is large during one beat period which produces large fluctuations in the transit time required for ultrasonic waves to travel from the transducer to the heart and back. This paper proposes a new method for overcoming this problem and accurately measuring small vibrations of the ventricle wall using ultrasound. In this method, the demodulated ultrasound signal reflected at the heart wall is converted from analogue to digital (A/D) signal at a high sampling frequency; from the resultant digital signal, the velocity of the wall is accurately obtained over a wide dynamic range based on the Doppler effect. The proposed method is preliminarily applied to the detection of small vibrations on the aortic wall and the interventricular septum. The new method offers potential for research in acoustical diagnosis of heart and artery dysfunction.