Increasing filtration thickness in an X-ray tube has which effect on beam quality?

• A. Beam quality decreases
• B. No change in beam quality
• C. Beam quality increases
• D. Dose rate increases

Answer: (C)

Increasing filtration thickness hardens the X-ray beam by removing the low-energy, less penetrating photons from the spectrum. This shifts the transmitted photons toward higher energies, raising the beam’s average energy and its penetrating power, which is what we mean by beam quality. In practical terms, the half-value layer increases, reflecting a tougher beam. While the quality goes up, the overall number of photons reaching the target or detector decreases, so the dose rate for a given exposure tends to drop rather than rise.