Which major interaction between x-ray photons and tissue results in total absorption of the incident photon?

Which major interaction between x-ray photons and tissue results in total absorption of the incident photon?

• A. Photoelectric effect
• B. Compton scatter
• C. Bremsstrahlung
• D. Coherent/Classical

Answer: (A)

The key idea is a photon being fully absorbed by an atom. In the photoelectric effect, the incoming x-ray photon is completely absorbed, and its energy is used to overcome the binding energy of an inner-shell electron, which is then ejected. The photon disappears from the beam, leaving no scattered photon behind. This contrasts with other interactions: Compton scatter transfers only part of the photon's energy to an electron and results in a photon that is deflected with lower energy, so the incident photon isn’t fully absorbed. Bremsstrahlung is radiation produced by accelerating electrons and not a mechanism for absorbing the incident photon. Coherent (elastic) scattering transfers little to no energy and the photon exits the interaction essentially unchanged. Therefore, the photoelectric effect is the interaction that results in total absorption of the incident photon.

The key idea is a photon being fully absorbed by an atom. In the photoelectric effect, the incoming x-ray photon is completely absorbed, and its energy is used to overcome the binding energy of an inner-shell electron, which is then ejected. The photon disappears from the beam, leaving no scattered photon behind. This contrasts with other interactions: Compton scatter transfers only part of the photon's energy to an electron and results in a photon that is deflected with lower energy, so the incident photon isn’t fully absorbed. Bremsstrahlung is radiation produced by accelerating electrons and not a mechanism for absorbing the incident photon. Coherent (elastic) scattering transfers little to no energy and the photon exits the interaction essentially unchanged. Therefore, the photoelectric effect is the interaction that results in total absorption of the incident photon.