Which type of focusing decreases the frame rate?

• A. Mechanical focusing
• B. Dynamic receive focusing
• C. Multiple transmit focusing
• D. Curved crystal focusing

Answer: (C)

Frame rate is how many image frames you can display per second, and it’s driven by how long it takes to send pulses, receive echoes, and process the data for each scan line. When you use multiple transmit focusing, several focused beams are sent to create multiple focal zones at different depths. Each additional transmit adds travel time for the pulse and its echoes, so the time per line increases and the overall frame rate drops. Dynamic receive focusing, on the other hand, adjusts the receive delays to improve focus without needing extra transmitted pulses, so it doesn’t reduce frame rate. Fixed focusing methods like mechanical or curved crystal focusing rely on hardware geometry to set a single focal point and don’t require extra transmissions, so they don’t inherently lower frame rate.