Which statement about the effect of filtration on patient dose is true?

• A. Filtration Reduces Low-Energy Photons And Thereby Reduces Patient Dose
• B. Filtration Reduces High-Energy Photons And Reduces Dose
• C. Filtration Increases Patient Dose
• D. Filtration Has No Effect On Patient Dose

Answer: (A)

Filtration works by hardening the x-ray beam: it absorbs the low-energy photons that would mostly be absorbed by the patient’s superficial tissues. Those low-energy photons contribute to skin dose without improving image quality, so removing them lowers the dose the patient receives while still preserving enough higher-energy photons to create a diagnostic image. The filter doesn’t primarily remove high-energy photons; it shifts the spectrum toward higher average energy, which means less energy deposited in superficial tissues and thus a lower overall patient dose. This is why the statement about filtration reducing low-energy photons and thereby reducing patient dose is the best choice.