How does increasing kVp affect image contrast?

How does increasing kVp affect image contrast?

• A. Increases contrast
• B. Decreases contrast
• C. No effect on contrast
• D. Increases contrast only for very small parts

Answer: (B)

Raising kVp makes the x-ray beam more penetrating, so photons pass through tissues with less variation in attenuation. At low kVp, attenuation differences are largely due to photoelectric absorption, which is strongly related to tissue density and atomic number, producing high contrast. As kVp increases, Compton scattering becomes more prevalent and attenuation differences between tissues become smaller, leading to a more uniform, gray image with reduced contrast. So increasing kVp generally lowers image contrast. The other options imply no change or an increase in contrast with higher energy, which doesn’t reflect how the interaction processes alter tissue attenuation across most clinical situations.

Raising kVp makes the x-ray beam more penetrating, so photons pass through tissues with less variation in attenuation. At low kVp, attenuation differences are largely due to photoelectric absorption, which is strongly related to tissue density and atomic number, producing high contrast. As kVp increases, Compton scattering becomes more prevalent and attenuation differences between tissues become smaller, leading to a more uniform, gray image with reduced contrast. So increasing kVp generally lowers image contrast. The other options imply no change or an increase in contrast with higher energy, which doesn’t reflect how the interaction processes alter tissue attenuation across most clinical situations.