If the frame rate increases and lines per frame are unchanged, what option best describes the change that occurs?

If the frame rate increases and lines per frame are unchanged, what option best describes the change that occurs?

• A. Ultrasound speed increases
• B. Frequency increases
• C. Depth increases
• D. Depth decreases

Answer: (D)

Frame rate is how many images are produced each second, and it depends on how long it takes to scan the depth of the frame for all lines. The time to acquire a frame is tied to the round-trip travel distance of the ultrasound pulse to the deepest point in the image. If the number of lines per frame stays the same and the speed of sound in tissue is unchanged, making depth shallower shortens the travel time per line. Shorter travel times allow more lines to be acquired in the same amount of time, so the frame rate increases. Therefore, when frame rate increases while lines per frame are unchanged, depth must decrease. The other options don’t explain this direct relationship under the given conditions: the speed of sound remains constant in tissue, deeper imaging would slow the frame rate, and changing frequency doesn’t directly affect frame rate in this scenario.

Frame rate is how many images are produced each second, and it depends on how long it takes to scan the depth of the frame for all lines. The time to acquire a frame is tied to the round-trip travel distance of the ultrasound pulse to the deepest point in the image. If the number of lines per frame stays the same and the speed of sound in tissue is unchanged, making depth shallower shortens the travel time per line. Shorter travel times allow more lines to be acquired in the same amount of time, so the frame rate increases. Therefore, when frame rate increases while lines per frame are unchanged, depth must decrease. The other options don’t explain this direct relationship under the given conditions: the speed of sound remains constant in tissue, deeper imaging would slow the frame rate, and changing frequency doesn’t directly affect frame rate in this scenario.