X-ray equipment made of aluminum and located in the primary x-ray beam to preferentially absorb or eliminate the less penetrating x-rays before they reach a patient is called a(an):

• A. collimator
• B. inherent shielding
• C. added filtration
• D. grid

Answer: (C)

Beam filtration removes the least penetrating photons from the primary x‑ray beam to harden it, which lowers patient skin dose without compromising the useful image information. When aluminum is placed in the beam path, it acts as added filtration: it sits outside the tube and selectively absorbs those low-energy photons that would otherwise contribute to dose but not to image quality. This is different from inherent filtration, which is the filtration already built into the tube housing and window. A collimator, on the other hand, shapes the beam rather than filtering its energy, and a grid is used to reduce scattered radiation at the image receptor after the beam passes through the patient. So the described setup corresponds to added filtration.