Which concept describes the ability to distinguish closely spaced structures in an image?

• A. Spatial resolution
• B. Modulation transfer function
• C. Contrast resolution
• D. Bit depth

Answer: (A)

Spatial resolution describes the imaging system’s ability to distinguish two closely spaced structures as separate. When two details are near each other, high spatial resolution lets you see them as distinct edges rather than a single blurred feature. This is influenced by factors like using a smaller focal spot, maintaining an optimal source-to-image distance, employing a detector with finer pixel size, and minimizing motion to reduce blur. The modulation transfer function is a related, quantitative way to describe how well the system preserves contrast at different spatial frequencies, but the fundamental concept asked for is the ability to resolve small, nearby details. Contrast resolution focuses on gray-scale differences rather than spatial separation, and bit depth affects the number of gray levels, not the ability to distinguish adjacent structures.