Basic study on angular dependence of ultrasonic scattering from wire phantom mimicking myocardium

Abstract

It is reported that the ultrasonic scattering from myocardium varies periodically during a cardiac cycle. One of the reasons is considered to be the change of the angle between the ultrasonic beam and the direction of myocardial fibers. Therefore, it is expected that ultrasonic scattering from myocardium quantitatively characterizes the condition of myocardium. To investigate the angle dependence of ultrasonic scattering in relation to the fiber direction, in this study, ultrasonic echoes from a wire phantom (thinner than a wavelength in diameter) that mimics myocardium were measured as a function of the insonification angle. Two ultrasonic transducers of 7 MHz were employed for transmitting and receiving ultrasonic pulses. Focal points of these transducers were set at the same point on the phantom. A custom-made experimental system can change the azimuth and elevation angles while keeping the focal points at the same point. Measured ultrasonic scattering showed a significant change depending on the azimuth angle. Such changes depending on the azimuth angle were decreased by increasing the elevation angle. These preliminary findings support the hypothesis that the change in the angle between the ultrasonic beam and myocardial fibers due to the heartbeat varies the ultrasonic scattering property.