How does increasing filtration thickness affect the quantity of the x-ray beam?

• A. No Change in quantity
• B. Decreased quantity
• C. Increased quantity
• D. Variable

Answer: (B)

Increasing filtration thickness cuts down the number of photons that make it to the patient or detector. The filter absorbs photons as they pass through, and low-energy photons are absorbed more readily. As you add more material, a larger fraction of the beam is attenuated, so the total photon count reaching the image receptor decreases. The beam ends up with a higher average energy (better quality), but fewer photons in total. So the quantity goes down, while the quality goes up. If you still need the same receptor exposure, you’d need to increase exposure factors accordingly.