What happens to axial resolution when the pulse duration is shortened?

What happens to axial resolution when the pulse duration is shortened?

• A. It improves
• B. It worsens
• C. It remains the same
• D. It becomes unpredictable

Answer: (A)

Shorter pulse duration reduces the spatial pulse length, which directly improves axial resolution. Axial resolution is tied to how long the pulse occupies tissue along the beam—the spatial pulse length (SPL). SPL equals the number of cycles in the pulse times the wavelength, so fewer cycles in the same time frame mean a shorter SPL. Since axial resolution is roughly SPL/2, a shorter SPL lets the system distinguish reflectors that are closer together along the axis, enhancing resolution. The other options would imply no improvement, a worsening, or unpredictability, which conflicts with the clear link between shorter pulse duration, shorter SPL, and better axial separation.

Shorter pulse duration reduces the spatial pulse length, which directly improves axial resolution. Axial resolution is tied to how long the pulse occupies tissue along the beam—the spatial pulse length (SPL). SPL equals the number of cycles in the pulse times the wavelength, so fewer cycles in the same time frame mean a shorter SPL. Since axial resolution is roughly SPL/2, a shorter SPL lets the system distinguish reflectors that are closer together along the axis, enhancing resolution. The other options would imply no improvement, a worsening, or unpredictability, which conflicts with the clear link between shorter pulse duration, shorter SPL, and better axial separation.