When imaging deeper, PRF is ______.

When imaging deeper, PRF is ______.

• A. Higher
• B. Lower
• C. Related
• D. Depth dependent

Answer: (B)

Pulse repetition frequency is governed by how quickly echoes from the deepest part of the image can return before the next pulse is fired. The deeper you image, the longer the round-trip travel time (2 × depth) for sound to reach that depth and come back. To avoid overlap of echoes from successive pulses, the system must reduce how often it sends pulses as depth increases. In practical terms, the maximum PRF is limited by roughly c/(2 × depth), where c is the speed of sound in tissue, so deeper imaging requires a lower PRF. Higher PRF would lead to range ambiguity and misinterpretation of where echoes originate. The choice that best fits is a lower PRF.

Pulse repetition frequency is governed by how quickly echoes from the deepest part of the image can return before the next pulse is fired. The deeper you image, the longer the round-trip travel time (2 × depth) for sound to reach that depth and come back. To avoid overlap of echoes from successive pulses, the system must reduce how often it sends pulses as depth increases. In practical terms, the maximum PRF is limited by roughly c/(2 × depth), where c is the speed of sound in tissue, so deeper imaging requires a lower PRF. Higher PRF would lead to range ambiguity and misinterpretation of where echoes originate. The choice that best fits is a lower PRF.