Which statement correctly describes the relationship between kilovoltage peak (kVp) and differential attenuation?

• A. Increased differential attenuation
• B. Decreased differential attenuation
• C. No change
• D. Variable depending on exposure

Answer: (B)

Increasing kVp raises the energy of the X-ray beam, making it more penetrating. At lower kVp, the photoelectric effect dominates and is highly dependent on tissue atomic number, so bone and soft tissue attenuate very differently, giving strong differential attenuation (high contrast). As kVp increases, Compton scattering becomes more prevalent and depends mainly on electron density, so attenuation differences between tissues become less pronounced. The result is a decrease in differential attenuation, which lowers image contrast. Exposure changes brightness but does not alter the inherent difference in how tissues attenuate at a given energy, so it doesn’t reverse this relationship.