Which resolution is determined by the spatial pulse length?

Which resolution is determined by the spatial pulse length?

• A. Axial
• B. Radial
• C. Image
• D. Angular

Answer: (A)

Axial resolution is determined by spatial pulse length. This measures how well two reflectors that lie along the beam’s path can be distinguished from one another. The spatial pulse length is the distance of one complete pulse in tissue, equal to the number of cycles in the pulse times the wavelength. Shorter spatial pulse length means the pulse occupies less distance, so echoes from closely spaced interfaces return at more distinct times and can be separated as separate echoes. You can shorten SPL by using a higher-frequency transducer (which has a shorter wavelength) or by delivering fewer cycles per pulse, though higher frequency reduces penetration due to greater attenuation. Other forms of resolution depend on different factors—lateral (beam-width) resolution on focusing and beam width, and angular or general image resolution on geometry and scanning—so they’re not set by spatial pulse length.

Axial resolution is determined by spatial pulse length. This measures how well two reflectors that lie along the beam’s path can be distinguished from one another. The spatial pulse length is the distance of one complete pulse in tissue, equal to the number of cycles in the pulse times the wavelength. Shorter spatial pulse length means the pulse occupies less distance, so echoes from closely spaced interfaces return at more distinct times and can be separated as separate echoes. You can shorten SPL by using a higher-frequency transducer (which has a shorter wavelength) or by delivering fewer cycles per pulse, though higher frequency reduces penetration due to greater attenuation. Other forms of resolution depend on different factors—lateral (beam-width) resolution on focusing and beam width, and angular or general image resolution on geometry and scanning—so they’re not set by spatial pulse length.