What technique enables focusing at multiple depths and across the beam, and how does it affect image quality?

• A. Dynamic focusing (phased-array techniques) improves lateral resolution at multiple depths and stabilizes beamwidth
• B. Static focusing improves frame rate but worsens lateral resolution
• C. No focusing technique can affect multiple depths
• D. Dynamic focusing reduces penetration depth without improving resolution

Answer: (A)

Dynamic focusing using phased-array techniques allows the beam to be focused at multiple depths and across the beam by applying electronic delays to the array elements. During transmission, these delays steer and converge the wavefront at chosen depths; during reception, the delays are adjusted so echoes from those depths are coherently summed. This creates several focal zones along the beam, keeping the beam narrow over a wider depth range. The payoff is improved lateral resolution across the image, with more uniform sharpness and better separation of adjacent structures, because the beam does not blur as it travels deeper. It doesn’t inherently change penetration depth, and while using multiple focal zones can impact frame rate, modern systems balance focusing with imaging speed to maintain overall image quality.