Which of the following statements about increasing kVp is true?

• A. As kVp increases, Compton interactions increase and image contrast increase
• B. As kVp increases, Compton interactions decrease and image contrast decrease
• C. As kVp increases, Compton interactions stay the same and image contrast stays the same
• D. As kVp increases, the percentage of Compton interactions increases and image contrast decreases

Answer: (D)

Raising kVp increases photon energy, which shifts the balance of interactions in tissue from photoelectric absorption toward Compton scattering. The photoelectric effect drops off quickly with energy, while the probability of Compton scattering stays relatively higher, so the beam ends up with a larger fraction of Compton interactions. Scatter from these Compton events reaches the image receptor and reduces image contrast, because it adds exposure without preserving tissue-dependent attenuation. So the statement that the percentage of Compton interactions increases and image contrast decreases is the best description of what happens when kVp is increased. The other options imply no change or the opposite effect on contrast, which doesn’t fit the physics of how energy affects interaction probabilities and image formation.