The ability to distinguish between adjacent structures that produce echoes of similar amplitude is termed:

• A. Spatial resolution
• B. Axial resolution
• C. Contrast resolution
• D. Temporal resolution

Answer: (C)

Contrast resolution is the capacity to distinguish adjacent tissues that return echoes with similar strength. When two nearby structures have echoes of nearly the same amplitude, they can appear with similar brightness on the image unless there are enough gray-scale levels to reveal subtle differences in echogenicity. This is separate from spatial resolution (how close two structures can be and still be seen as separate) and temporal resolution (how quickly frames are acquired). Improving contrast resolution involves using a wider gray-scale range so subtle differences in echogenicity become visible, allowing those similar-amplitude echoes to be distinguished.