In which interaction is the average energy of the photon approximately one-third of the kilovolt peak (kVp) selected at the control panel?

In which interaction is the average energy of the photon approximately one-third of the kilovolt peak (kVp) selected at the control panel?

• A. Compton interaction
• B. Photoelectric interaction
• C. Characteristic interaction
• D. Bremsstrahlung interaction

Answer: (D)

Bremsstrahlung radiation is produced when high-speed electrons are decelerated in the nuclear field of the target. This creates photons over a broad, continuous spectrum that runs from near zero up to a maximum energy equal to the incident electron energy (the kVp setting). Because the spectrum is weighted toward lower-energy photons, its average energy ends up around one-third of the maximum energy. Since the maximum corresponds to the kVp, the average photon energy is roughly one-third of kVp in this interaction. Other interactions don’t fit this pattern. In photoelectric absorption, the emitted photon energy is tied to the incident photon energy minus binding energy and has no characteristic value tied to a simple fraction of kVp. Characteristic radiation produces photons with fixed energies determined by atomic transitions, unrelated to the tube kVp. Compton scattering yields scattered photons whose energy depends on the scattering angle, not a fixed fraction of kVp.

Bremsstrahlung radiation is produced when high-speed electrons are decelerated in the nuclear field of the target. This creates photons over a broad, continuous spectrum that runs from near zero up to a maximum energy equal to the incident electron energy (the kVp setting). Because the spectrum is weighted toward lower-energy photons, its average energy ends up around one-third of the maximum energy. Since the maximum corresponds to the kVp, the average photon energy is roughly one-third of kVp in this interaction.

Other interactions don’t fit this pattern. In photoelectric absorption, the emitted photon energy is tied to the incident photon energy minus binding energy and has no characteristic value tied to a simple fraction of kVp. Characteristic radiation produces photons with fixed energies determined by atomic transitions, unrelated to the tube kVp. Compton scattering yields scattered photons whose energy depends on the scattering angle, not a fixed fraction of kVp.