Which focusing technique forms a beam with a fixed focus during transmission using programmed delays?

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

Answer: (D)

Focusing during transmission using programmed delays is electronic transmit focusing. By applying precise time delays to each element of the transducer during emission, the emitted wavefronts are arranged to meet at a chosen focal point. This makes the beam converge at that depth, giving a fixed focus as the sound leaves the probe. Dynamic receive focusing would adjust focus while the echoes are received, not during transmission; elevational focusing targets the beam in the perpendicular (out-of-plane) direction; mechanical focusing uses a fixed physical lens. So, the transmit focus description matches the idea of forming a beam with a fixed focal point during transmission via delays.