Which term refers to the measurement of how clearly small, closely spaced structures can be resolved in an image?

• A. Spatial resolution
• B. Detective Quantum Efficiency
• C. Radioactive contamination
• D. Biologic half-life

Answer: (A)

Spatial resolution is a measure of how clearly small, closely spaced structures can be resolved in an image. It describes the ability to distinguish two nearby features as separate rather than merging into one. The higher the spatial resolution, the smaller the distance between features that can still be told apart. This depends on the imaging system’s optics or detector, sampling density, and how blurred the image is by the system’s inherent blur (the point spread function). In practice, resolution is often described in terms of line pairs per millimeter or the minimum resolvable distance. To improve it, you can use finer sampling (smaller pixels), sharper optics or shorter effective wavelengths, and reduction of blur and noise. The other terms don’t measure this clarity of detail: Detective Quantum Efficiency relates to how efficiently the detector converts photons into signal while preserving signal-to-noise, whereas radioactive contamination and biologic half-life pertain to radiation safety and biological kinetics, not image resolution.