Which factor is least likely to limit spatial resolution in screen-film mammography?

• A. Focal spot size of the X-ray tube
• B. Film-screen contact quality
• C. Phosphor screen granularity
• D. Processing developer temperature

Answer: (D)

Spatial resolution is about how sharply small details can be seen in the image. In screen-film mammography, the sharpness is mainly governed by how the image is formed: the X-ray source is not a perfect point, so a finite focal spot size creates geometric unsharpness (penumbra) that blurs fine details. If the screen and film aren’t in intimate contact, light from the screen can spread before it reaches the film, reducing sharpness. The phosphor screen itself also matters: larger phosphor granules scatter light more, blunting fine structures, while finer granularity preserves detail.

Processing temperature, on the other hand, changes how the film develops in terms of density and contrast, not the inherent sharpness of the image. It can affect overall visibility or graininess in a broad sense, but it does not directly limit spatial resolution. So the factor least likely to limit resolution is the processing developer temperature.