If lines per frame are changed while imaging depth remains constant, what else would change?

If lines per frame are changed while imaging depth remains constant, what else would change?

• A. PRF
• B. Period
• C. Frame rate
• D. Image contrast

Answer: (C)

When depth is fixed, the time needed to acquire each line is basically constant because it’s determined by the round‑trip travel time to that depth. If you increase the number of lines per frame, you must spend more time filling that frame, so frames per second drop. The pulse repetition frequency (and thus the period) is set by depth and speed of sound, so it stays essentially the same. Image contrast is governed by signal processing and tissue properties, not by how many lines you sample per frame, so it doesn’t change in this scenario. Therefore, the frame rate is the quantity that changes.

When depth is fixed, the time needed to acquire each line is basically constant because it’s determined by the round‑trip travel time to that depth. If you increase the number of lines per frame, you must spend more time filling that frame, so frames per second drop. The pulse repetition frequency (and thus the period) is set by depth and speed of sound, so it stays essentially the same. Image contrast is governed by signal processing and tissue properties, not by how many lines you sample per frame, so it doesn’t change in this scenario. Therefore, the frame rate is the quantity that changes.