How does increasing line density affect frame rate in 2D ultrasound?

• A. Reduces frame rate
• B. Increases frame rate
• C. Has no effect
• D. Only affects depth penetration

Answer: (A)

Increasing line density means more scan lines are needed to cover the same area in one frame. Each line requires an ultrasound pulse and the corresponding data to be acquired and processed. So as you add more lines, the time to complete a single frame grows, and the number of frames you can display per second (the frame rate) goes down. This is a trade-off: higher line density gives better lateral resolution, but it slows the frame rate. If line density doubles, the frame rate roughly halves, assuming other factors stay the same. It doesn’t primarily change depth penetration, which is governed more by frequency, power, and attenuation, not by how many lines are used per frame.