Which statement about adjusting PRF in practice is true?

• A. It can be adjusted by changing depth of view
• B. It can be adjusted by changing gain
• C. It can be adjusted by changing transducer frequency
• D. It cannot be adjusted

Answer: (A)

PRF equals the number of ultrasound pulses emitted per second, and it’s governed by the time the system must wait for echoes from the deepest part of the image before sending the next pulse. When you view a shallower depth, echoes return more quickly, so the system can fire pulses more often and PRF increases. When you image deeper, echoes take longer to return, so the system must pause longer between pulses, and PRF decreases. Gain and transducer frequency affect signal strength and image quality, not the timing of pulses, so they don’t change PRF. Deselecting depth isn’t required here because adjusting the depth of view is the practical way to change PRF, making this statement true.