What type of focusing is performed by delay circuitry upon reception?

• A. Elevational focusing
• B. Transmit focus
• C. Mechanical focusing
• D. Dynamic receive focusing

Answer: (D)

Focusing on reception is about aligning the signals from all array elements so that echoes from a chosen depth arrive in sync and sum constructively. The delay circuitry applies depth-dependent time shifts to each received channel, compensating for the different travel times from the focal point to each element.

Why this is dynamic: as you drill through the image depths, the system updates these delays for different focal depths, maintaining a sharp focus across the entire depth range. This is done in real time with digital beamforming, so the receive beam is continually refocused as you scan.

Elevational focusing concerns the dimension perpendicular to the imaging plane (slice thickness) and is not about the receive-time delays for depth. Transmit focus uses delays when emitting the pulse to shape the beam, and mechanical focusing relies on curved lenses or elements. The receiving-side, depth-dependent, time-shifted summation is dynamic receive focusing.