What is another name for longitudinal resolution?

• A. depth
• B. lateral
• C. axial
• D. transverse

Answer: (C)

Longitudinal resolution is the same as axial resolution. It describes how well two reflectors that lie along the path of the ultrasound beam (in the depth direction) can be distinguished from one another. This resolution is determined by the spatial pulse length—the length of the ultrasound pulse itself. Shorter pulses, achieved by using higher frequency or fewer cycles per pulse, reduce the spatial pulse length and improve axial resolution, letting closely spaced structures along the beam be resolved more clearly. Depth is simply how far away structures are, while lateral (or transverse) resolution concerns the ability to distinguish structures side by side across the image, perpendicular to the beam.