Using lower kilovoltage peak (kVp) increases the proportion of which interaction type during radiography?

• A. Photoelectric interactions
• B. Compton scatter
• C. Coherent scatter
• D. Pair production

Answer: (A)

Lower kilovoltage peak shifts the interaction balance toward photoelectric absorption. At lower photon energies, photoelectric interactions become more probable, especially with higher-atomic-number tissues, because their likelihood rises sharply as energy decreases (roughly inversely with the cube of energy). This means more photons are absorbed by atoms rather than scattered. Compton scattering, which involves scattered photons and is more prominent at higher energies, becomes less dominant in comparison as energy drops. Pair production isn’t a factor in diagnostic radiography because it requires energies above 1.022 MeV, far beyond typical kVp ranges, and coherent scattering, while possible at low energies, contributes less to image formation in this setting. So lowering kVp increases the proportion of photoelectric interactions.