Pulse-echo imaging

Pulse-echo imaging sends a short acoustic pulse and records echoes returning from interfaces or scatterers. If sound speed is approximately constant and the path is straight, an echo delay $t$ corresponds to range $r=ct/2$, because sound travels to the scatterer and back.

Scanning beam direction and measuring echo strength produces an image. Pulse duration and bandwidth affect axial resolution, while beam width affects transverse resolution. Incorrect sound-speed assumptions distort inferred positions, and multiple reflections can create echoes that do not correspond to a single direct round trip.