Angular scatter imaging in medical ultrasound

Ultrasonic imaging plays a critical diagnostic role in a broad range of medical specialties; however, there continue to be areas of clinical medicine where the advantages of ultrasound cannot be brought to bear because the targets of most interest do not exhibit sufficient image contrast. We have investigated a novel imaging method that utilizes modified ultrasonic imaging equipment to interrogate a previously unexploited source of image contrast, namely ultrasonic angular scatter variations. This technique takes advantage of the fact that the ultrasonic scattering from tissue changes with the angle between the incident (transmitted) ultrasonic wave and the observed (received) ultrasonic wave. Angular scatter variations result from spatial variations in the intrinsic material properties of density and compressibility, as well as the geometry of the tissue microstructure. We present experimental results from tissue mimicking and in vivo human tissues indicating that angular scatter differentiates targets that are indistinguishable in conventional ultrasound images. We also present cases where angular scatter images improve the contrast of interesting targets relative to conventional images. Early in vivo results from the myotendinous junction of the human gastrocnemius muscle indicate that different soft tissues have different angular scatter profiles and that these profiles can be used to discern between tissues.