What is the commonly cited spatial resolution limit for screen-film mammography, expressed in line pairs per millimeter (lp/mm)?

• A. 10 lp/mm
• B. 15 lp/mm
• C. 20 lp/mm
• D. 25 lp/mm

Answer: (B)

Spatial resolution in screen-film mammography is described in line pairs per millimeter, which reflects how finely a system can distinguish alternating light and dark details. For conventional screen-film setups, the practical limit is about 15 line pairs per millimeter. This comes from the combined resolving power of the intensifying screen, the film emulsion and lattice, and the processing workflow; all contribute blur and grain that degrade high-frequency information. At around 15 lp/mm, details such as microcalcifications and subtle tissue structures are still detectable with reliable contrast, but trying to push higher leads to noticeable blur and loss of visibility, making small features harder to interpret. Values significantly lower would underestimate what these systems can resolve, while higher values (like 20 or 25 lp/mm) exceed what standard screen-film hardware typically achieves.