The main purpose of time delays during receive focusing is to compensate for differences in distances to the reflector.

• A. To align echoes from different depths
• B. To compensate for distance differences to the reflector
• C. To attenuate noise
• D. To adjust echo amplitudes

Answer: (B)

Receive focusing uses time delays across the array to align echoes from a specific point in the tissue. Because echoes travel different distances to each element, they don’t arrive at the same time unless we compensate for those travel-time differences. By applying the right delays, the reflections from that point arrive simultaneously at the beamformer, so they add up coherently. This makes the received signal stronger and the image sharper at that depth.

So, the main purpose of these delays is to compensate for differences in distances to the reflector, not to attenuate noise or adjust amplitudes. As you change the focal point with different delays, the receive beam is steered and refocused to other depths.