About what percent of the X-rays interacting with intensifying screens actually interact?

• A. 10%
• B. 60%
• C. 30%
• D. 90%

Answer: (C)

Intensifying screens convert some of the incoming X-rays into visible light, but only a portion actually interact with the phosphor layer. For diagnostic-energy X-rays, the interaction efficiency is moderate, around one-third of the incident photons. In other words, about 30% of the X-rays interact with the screen, while the rest pass through or fail to produce light. This balance explains why screen speeds are finite and why exposure factors are set accordingly. The other values would imply unusually high or low interaction rates for typical screens, which isn’t characteristic of standard radiographic screens.