Which of the following is accomplished by appropriate filtration?

• A. 1, 2 and 3
• B. 1 and 2
• C. 2 and 3
• D. 1 and 3

Answer: (A)

Filtration shapes the x-ray beam by removing the lowest-energy photons before they reach the patient. Those soft photons would be absorbed in superficial tissues and contribute to dose without providing meaningful information, so eliminating them reduces patient dose, including skin dose. In doing so, the beam becomes harder and more penetrating, which improves the quality of the image by reducing soft-tissue attenuation and scatter that can blur contrast. The result is a beam with a higher average energy (a defined HVL) that still delivers enough exposure to the image receptor but with less unnecessary dose to the patient. Because of these effects, appropriate filtration accomplishes all the intended outcomes: lower patient dose, better image quality, and a properly hardened beam for consistent imaging.