If the spatial pulse length is 10 mm, what is the axial resolution?

If the spatial pulse length is 10 mm, what is the axial resolution?

• A. 0.5 cm
• B. 5 cm
• C. 10 mm
• D. 1 cm

Answer: (A)

Axial resolution is determined by how long the emitted pulse lasts in tissue; it’s roughly half the spatial pulse length. This is because two reflectors along the beam need to be separated by at least half the pulse length to be distinguished as separate echoes. So with a spatial pulse length of 10 mm, the axial resolution is SPL/2 = 5 mm, which is 0.5 cm. Shorter pulses (smaller SPL) give better axial resolution, while longer pulses reduce it. The other values would correspond to the full pulse length or larger, not the resolvable axial distance.

Axial resolution is determined by how long the emitted pulse lasts in tissue; it’s roughly half the spatial pulse length. This is because two reflectors along the beam need to be separated by at least half the pulse length to be distinguished as separate echoes. So with a spatial pulse length of 10 mm, the axial resolution is SPL/2 = 5 mm, which is 0.5 cm. Shorter pulses (smaller SPL) give better axial resolution, while longer pulses reduce it. The other values would correspond to the full pulse length or larger, not the resolvable axial distance.