As depth of view increases, PRP tends to

• A. Decrease
• B. Increase
• C. Remain the same
• D. Oscillate

Answer: (B)

The concept here is how imaging depth affects the timing between ultrasound pulses. PRP, or pulse repetition period, is the time interval between sending one pulse and the next. When you image deeper into tissue, echoes from the deepest structures take longer to return. To ensure those echoes are received before the next pulse is emitted, the system must wait longer, so PRP increases with depth. Since the speed of sound in tissue is fairly constant, PRP is effectively proportional to depth, making deeper views require a longer PRP. A shorter PRP wouldn’t give enough time for deep echoes to return, and PRP staying the same or oscillating wouldn’t reflect the need to accommodate deeper imaging. Also, increasing PRP means the pulse repetition frequency decreases, which is the reciprocal relationship you’d expect. So the correct result is that PRP increases as depth of view increases.