If the frame rate rises and the lines per frame remain the same, the imaging depth must do what?

If the frame rate rises and the lines per frame remain the same, the imaging depth must do what?

• A. Depth decreases
• B. Depth increases
• C. Depth remains unchanged
• D. Depth cannot be determined

Answer: (A)

Frame rate is determined by how long it takes to acquire one frame. If the number of lines per frame stays the same, boosting the frame rate means each line must be acquired more quickly. The time to acquire a line equals the round-trip travel time of the ultrasound pulse to the deepest point in the image. Since the speed of sound in tissue is essentially constant, deeper imaging requires more time for the echoes to return, which reduces the frame rate. To increase frame rate while keeping lines per frame fixed, you must shorten the maximum depth being imaged. So the imaging depth must decrease.

Frame rate is determined by how long it takes to acquire one frame. If the number of lines per frame stays the same, boosting the frame rate means each line must be acquired more quickly. The time to acquire a line equals the round-trip travel time of the ultrasound pulse to the deepest point in the image. Since the speed of sound in tissue is essentially constant, deeper imaging requires more time for the echoes to return, which reduces the frame rate. To increase frame rate while keeping lines per frame fixed, you must shorten the maximum depth being imaged. So the imaging depth must decrease.