Increasing the number of transmit focal zones and optimizing their location primarily improves which aspect?

• A. Increases frame rate
• B. Narrows the beam width at depth
• C. Degrades axial resolution
• D. Reduces penetration

Answer: (B)

Focusing the transmit beam to narrow its width at the depth of interest is what happens when you add more transmit focal zones and optimize their locations. This narrower beam at the focal depth sharpens lateral detail, so structures that are side by side along the scan line are distinguished more clearly. Axial resolution depends on pulse length and frequency, not on focusing, and penetration isn’t directly improved or worsened by adding focal zones. The trade-off is typically frame rate, which can decrease because more transmitting is required to cover multiple focal zones.