Ultrasonic Reflex Transmission Imaging

Reflex Transmission Imaging (RTI) is a new imaging method by which orthographic transmission images can be made using augmented B-mode equipment. Conventional transmission imaging requires acoustic coupling to large areas on both sides of the body, whereas RTI can be performed from one side with a single, small transducer probe. In this mode, transmission images in a plane normal to the beam are made by integrating the reverberations from beyond the focal zone of the transducer. These reverberations provide, in essence, a source of incoherent insonification from behind the focal plane.

Preliminary in-vitro images have been made using a computer-interfaced rectilinear scanner with a 1-inch diameter f/2.8 transducer. The images have good resolution and signal-to-noise ratio, and a short depth-of-field. Backscatterer inhomogeneity is well smoothed.

Transmission images provide information that is complementary to B-scans. RTI will allow both to be made with the same instrument and presented on the same display. A time-gated reflection C-scan could be generated simultaneously. Other RTI modes, including an attenuation B-mode, also are discussed.