Acoustic beam anomalies in automated breast imaging

Abstract

In B-mode imaging of the dependent or compressed breast, wave incidence at steep angles can change propagation directions and induce areas of signal dropout. To evaluate the image anomalies in reasonable simulation times, we performed full-wave studies for center frequencies of 1 and 4 MHz. Speed of sound and density of skin, typical coupling gel, and adipose tissue were assigned to the test couplant. Compared with commercial gel, skin-like couplant reduced the dropout area at 1 and 4 MHz by 57.1% and 96.7%, respectively, consistent with a decreased average beam deflection in the breast. Conversely, the adipose-like couplant increased the dropout area from that of simulated commercial gel by 26.5% and 36.7% at 1 and 4 MHz, respectively. In addition, the skin-like couplant resulted in the greatest beam deflection inside the breast among all couplants. The findings could aid the use of three-dimensional simulations to design ultrasound couplants for beam passage through tissue boundaries at steep angles to improve corrections of signal dropout and defocusing and in compound imaging.

Ultrasonic Imaging: Physics and Mechanism

“…21 shows simulation and imaging examples of beam refraction[57]. In the simulation (left panel) a sound beam travels upwards through ultrasound gel (medium 1 ) towards a human skin interface (double parallel curved lines, medium 2 ).…”

“…1.21 Examples of refraction image artifacts. Left panel: Simulation of an acoustic beam emerging from the bottom, traveling through ultrasound coupling gel (medium 1 ) and being refracted to the right by the curved skin surface (medium 2 ) into breast tissue (medium 3 ) [57].Right panel: Clinical refraction example of a hypoechoic region below the skin surface[57]…”