Which statement is not true regarding lateral resolution?

Which statement is not true regarding lateral resolution?

• A. It is equal to beam width
• B. It is improved by focusing
• C. It is defined as the minimum separation required to resolve two structures perpendicular to the beam axis
• D. It remains constant throughout scanning depth

Answer: (D)

Lateral resolution is determined by the width of the ultrasound beam perpendicular to its axis, and that width changes with depth due to diffraction. The beam tends to be narrow at the focus, where focusing sharpens the resolution, and it broadens as you move away from the focal zone, which worsens the resolution. Because of this depth-dependent beam width, lateral resolution does not stay constant throughout scanning depth. It is best at the focus and deteriorates with increased distance from that focus, while still representing the minimum lateral separation needed to distinguish two structures side by side at a given depth.

Lateral resolution is determined by the width of the ultrasound beam perpendicular to its axis, and that width changes with depth due to diffraction. The beam tends to be narrow at the focus, where focusing sharpens the resolution, and it broadens as you move away from the focal zone, which worsens the resolution. Because of this depth-dependent beam width, lateral resolution does not stay constant throughout scanning depth. It is best at the focus and deteriorates with increased distance from that focus, while still representing the minimum lateral separation needed to distinguish two structures side by side at a given depth.