Which value is frequently cited as the practical limit of spatial resolution in screen-film mammography?

• A. 10 lp/mm
• B. 12 lp/mm
• C. 18 lp/mm
• D. 15 lp/mm

Answer: (D)

The practical spatial resolution in screen-film mammography is set by the whole imaging chain, not just the film, and is commonly described in line pairs per millimeter (lp/mm). The system’s ability to separate fine alternating light and dark patterns is limited by factors such as focal spot blur, screen-film interaction, film grain, and viewing conditions. Historically, this combination yields about 15 lp/mm as the typical upper limit for what can be reliably resolved in clinical practice. That corresponds to roughly 0.03 mm features (about 33 microns per line or space), which is why 15 lp/mm is often cited as the practical limit. Values like 10 or 12 lp/mm are lower than what's routinely achievable, while 18 lp/mm exceeds the standard capability of conventional screen-film systems.