Changing from SP-100 screens to SP-400 screens will reduce exposure settings and patient dose by what percent for the same film density?

Changing from SP-100 screens to SP-400 screens will reduce exposure settings and patient dose by what percent for the same film density?

• A. 50%
• B. 75%
• C. 25%
• D. 0%

Answer: (B)

Increasing the screen speed means more light is emitted per X-ray photon, so much less X-ray exposure is needed to reach the same film density. Moving from SP-100 to SP-400 is about four times faster, so the required exposure drops to roughly one-quarter of the original. That translates to about a 75% reduction in exposure settings and patient dose for the same film density. In practice, the exact percentage can vary with processing and imaging geometry, but the general rule is that a fourfold speed increase cuts dose by about three-quarters.

Increasing the screen speed means more light is emitted per X-ray photon, so much less X-ray exposure is needed to reach the same film density. Moving from SP-100 to SP-400 is about four times faster, so the required exposure drops to roughly one-quarter of the original. That translates to about a 75% reduction in exposure settings and patient dose for the same film density. In practice, the exact percentage can vary with processing and imaging geometry, but the general rule is that a fourfold speed increase cuts dose by about three-quarters.