Ultrasonic imaging of sum frequency components by crossed beam contrast echo method

Abstract

In a breast cancer diagnosis, the clinical usefulness of the contrast echo harmonic imaging has been reported. The authors proposed a contrast echo method by crossing the two ultrasonic beams to improve the accuracy. The microbubbles in the crossed region re-emit the secondary wave including the sum frequency components. It is capable of discriminating between the echo from microbubbles and the echo from tissue without microbubbles, since the sum frequency are not generated during the nonlinear propagation of primary wave outside the crossed region. Thus the contrast of the resultant image is improved. This study measured the sum frequency components in the echoes from the microbubbles of Sonazoid® in degassed water by using the ultrasonic imaging system with 64 channels. The ultrasonic wave of 5 MHz was transmitted from the array probe of central frequency of 6 MHz equipped with the imaging system. Since the beam formed by the array probe crossed the other beam of 2 MHz at the position 8 cm apart from th...