Decreasing filtration thickness has what effect on beam quality?

• A. Increased beam quality
• B. Decreased beam quality
• C. No change in beam quality
• D. Increased exposure time

Answer: (B)

Filtration shapes the energy spectrum of the x-ray beam. Beam quality reflects how penetrating the beam is, often described by its HVL (half-value layer). If you decrease filtration thickness, you remove fewer low-energy photons, so the beam becomes softer with more low-energy photons. Softer beams penetrate less, so the overall beam quality decreases. Increasing filtration would do the opposite—harder, more penetrating beam with higher quality. The choice about exposure time isn’t about beam quality itself, which is why the correct answer is that beam quality decreases.