Which statement about filtration and patient dose is true?

• A. Filtration reduces the dose by removing high-energy photons
• B. Filtration reduces the dose by removing low-energy photons
• C. Filtration has no effect on patient dose
• D. Filtration increases patient dose

Answer: (B)

Filtration reduces patient dose by removing low-energy photons from the x-ray beam. Those low-energy photons contribute to dose because they are readily absorbed by superficial tissues, but they don’t help form the image since they’re absorbed before reaching the detector. Filtering them out makes the beam harder, raising the average photon energy, which lowers skin and superficial doses and often improves image quality by reducing scattered radiation that can degrade contrast.

So the true statement is that filtration reduces dose by removing low-energy photons. Removing high-energy photons would not be beneficial for this purpose and would unnecessarily weaken the beam. Filtration does have an effect on dose, and it does not increase dose.