Which statement correctly describes the effect of short pulse duration on axial resolution?

Which statement correctly describes the effect of short pulse duration on axial resolution?

• A. Worse
• B. No effect
• C. Better
• D. Only affects lateral resolution

Answer: (C)

Short pulse duration reduces the spatial pulse length, which determines axial resolution. Axial resolution is roughly half the spatial pulse length, so with fewer cycles in the pulse (at the same center frequency) the pulse occupies less distance in tissue. That lets the system distinguish two reflectors that are closer along the beam path, so axial resolution improves. Lateral resolution depends on beam width and focusing, not on how long the pulse lasts, so changing pulse duration doesn’t improve lateral resolution.

Short pulse duration reduces the spatial pulse length, which determines axial resolution. Axial resolution is roughly half the spatial pulse length, so with fewer cycles in the pulse (at the same center frequency) the pulse occupies less distance in tissue. That lets the system distinguish two reflectors that are closer along the beam path, so axial resolution improves. Lateral resolution depends on beam width and focusing, not on how long the pulse lasts, so changing pulse duration doesn’t improve lateral resolution.