In clinical practice, the spatial resolution of screen-film mammography is commonly quoted as approximately

• A. 15 lp/mm
• B. 9 lp/mm
• C. 25 lp/mm
• D. 6 lp/mm

Answer: (A)

Spatial resolution in screen-film mammography is about how finely details can be resolved, quantified as line pairs per millimeter (lp/mm). In everyday clinical practice, the screen-film setup typically yields around 15 lp/mm, which is the level of detail that radiologists expect to be able to discern when evaluating mammograms. This value reflects the practical limits imposed by the physical components—the film grain and the screen phosphor size—along with the x-ray geometry, all of which shape the system’s ability to reproduce high-frequency details without excessive noise or loss of contrast. Values much higher, like 25 lp/mm, would require unrealistically fine film and screen characteristics for standard screening conditions, while values noticeably lower, such as 9 or 6 lp/mm, would indicate a system with poorer resolution than what is routinely used for diagnostic mammography.