An increase in x-ray beam filtration would

• A. Increases the number of Compton interactions
• B. All of the above
• C. Reduces contrast
• D. Increases the average photon energy

Answer: (B)

Increasing filtration trims off the low-energy part of the X-ray spectrum, so the beam becomes harder and the average photon energy rises. That higher-energy beam penetrates more efficiently and is more likely to undergo Compton scattering than photoelectric absorption in soft tissue, shifting the interaction pattern toward Compton events. At the same time, removing the soft photons reduces the differential attenuation between tissues, which lowers the image contrast. Because all of these effects occur with added filtration, the best choice is that all of the above are true.