What is the difference between inherent filtration and added filtration in terms of beam hardening and patient dose?

• A. Inherent filtration is fixed inside the tube; added filtration is adjustable; added filtration reduces low-energy photons, lowering patient dose and hardening the beam.
• B. Inherent filtration is adjustable; added filtration is fixed; added filtration increases low-energy photons.
• C. Inherent filtration reduces patient dose; added filtration does not affect beam quality.
• D. Inherent filtration increases beam hardening; added filtration decreases it.

Answer: (A)

Filtration shapes the x-ray beam by removing low-energy photons that would be absorbed by the patient without improving image quality. Inherent filtration is built into the tube assembly—the glass envelope, window, and any permanently fixed filters—and it cannot be changed during imaging. Added filtration is placed outside the tube along the beam path and is adjustable, allowing you to tailor the beam quality for different exams.

Because low-energy photons contribute most to patient skin dose but little to image formation, removing them with added filtration lowers the dose for a given image quality and hardens the beam (shifts the spectrum to higher energies). The more filtration you add, the harder the beam becomes, which can improve penetration and reduce dose efficiency demands, though it may require technique adjustments to maintain image brightness. So, the correct understanding is that inherent filtration is fixed inside the tube, added filtration is adjustable, and adding filtration reduces low-energy photons, lowers patient dose, and hardens the beam.