Which statement about filtration and beam quality is true?

• A. Inherent filtration removes low-energy photons
• B. Added filtration is built into the tube
• C. Filtration removes low-energy photons, increasing beam quality and reducing dose
• D. Filtration increases the number of high-energy photons

Answer: (C)

Filtration works by removing the lower-energy portion of the X-ray spectrum. Those soft photons are more likely to be absorbed in superficial tissues and contribute to dose without improving image quality. By absorbing them, the beam becomes “harder,” meaning the average energy rises, so beam quality improves (higher HVL) and the dose to the patient for the same image receptor exposure decreases.

Inherent filtration is the filtration built into the tube itself, while added filtration is placed in the beam path to adjust quality. Both achieve the same effect—filtering out low-energy photons to harden the beam. The idea that filtration simply increases the number of high-energy photons isn’t accurate; it’s about removing the low-energy photons to shift the spectrum toward higher energies, not creating more high-energy photons.