Which interaction is primarily responsible for dose deposition via recoil electrons and deflection of photons?

Which interaction is primarily responsible for dose deposition via recoil electrons and deflection of photons?

• A. Compton scattering
• B. Photoelectric absorption
• C. Coherent scattering
• D. Bremsstrahlung

Answer: (A)

Compton scattering is the interaction that best explains dose deposition via recoil electrons and deflection of photons. In this process, a photon collides with a loosely bound or free electron and transfers part of its energy to that electron, producing a recoil electron. The photon is scattered at an angle with reduced energy. The energy imparted to the recoil electron localizes as ionization and excitation along its path, contributing to the dose, while the scattered photon leaves in a different direction and may undergo further interactions. The amount of energy given to the electron depends on the scattering angle, with larger angles transferring more energy. Photoelectric absorption also deposits energy by ejecting an electron, but it results in the photon being absorbed rather than scattered, so there isn’t a deflected photon to account for. Coherent scattering involves scattering without meaningful energy transfer, so it contributes negligibly to dose. Bremsstrahlung involves electrons producing photons as they slow, which is a secondary pathway and not the primary mechanism described by recoil electrons accompanied by photon deflection.

Compton scattering is the interaction that best explains dose deposition via recoil electrons and deflection of photons. In this process, a photon collides with a loosely bound or free electron and transfers part of its energy to that electron, producing a recoil electron. The photon is scattered at an angle with reduced energy. The energy imparted to the recoil electron localizes as ionization and excitation along its path, contributing to the dose, while the scattered photon leaves in a different direction and may undergo further interactions. The amount of energy given to the electron depends on the scattering angle, with larger angles transferring more energy.

Photoelectric absorption also deposits energy by ejecting an electron, but it results in the photon being absorbed rather than scattered, so there isn’t a deflected photon to account for. Coherent scattering involves scattering without meaningful energy transfer, so it contributes negligibly to dose. Bremsstrahlung involves electrons producing photons as they slow, which is a secondary pathway and not the primary mechanism described by recoil electrons accompanied by photon deflection.