As beam filtration increases, image contrast typically changes how?

• A. Contrast increases
• B. There is no effect on contrast
• C. Contrast decreases
• D. Contrast increases because the beam is harder

Answer: (C)

Hardening the beam by increasing filtration removes low-energy photons, leaving a higher-energy spectrum. Those low-energy photons are more likely to be absorbed differently by various tissues, which boosts the contrast on the image. When they’re filtered out, the remaining photons penetrate more uniformly and interact with tissues in a way that reduces the differences in attenuation between structures. So the image contrast tends to decrease as filtration increases.