Which interaction contributes MOST to a patient's radiation dose during diagnostic radiography?

Which interaction contributes MOST to a patient's radiation dose during diagnostic radiography?

• A. Compton Scattering
• B. Photoelectric Effect
• C. Coherent Scattering
• D. Pair Production

Answer: (B)

The amount of radiation dose a patient receives is determined by how much energy is deposited in the body. The photoelectric interaction is most influential here because when a photon is absorbed by a bound inner-shell electron, the photon’s energy is deposited locally as the ejected photoelectron (and any subsequent shell transitions). This means a large portion of the incident photon’s energy ends up heating and ionizing the tissue right at the interaction site. The probability of photoelectric absorption is relatively high at diagnostic energies, especially in materials with higher effective atomic numbers, making it a major contributor to dose in typical imaging ranges. In contrast, coherent (Rayleigh) scattering involves almost no energy transfer to the tissue, pair production requires energies well above diagnostic X-rays and is negligible, and while Compton scattering does deposit energy via recoil electrons, the scattered photons can escape the body, so the energy deposited per interaction is generally less than the full energy absorbed in a photoelectric event. Therefore, photoelectric absorption contributes the most to patient dose during diagnostic radiography.

The amount of radiation dose a patient receives is determined by how much energy is deposited in the body. The photoelectric interaction is most influential here because when a photon is absorbed by a bound inner-shell electron, the photon’s energy is deposited locally as the ejected photoelectron (and any subsequent shell transitions). This means a large portion of the incident photon’s energy ends up heating and ionizing the tissue right at the interaction site. The probability of photoelectric absorption is relatively high at diagnostic energies, especially in materials with higher effective atomic numbers, making it a major contributor to dose in typical imaging ranges. In contrast, coherent (Rayleigh) scattering involves almost no energy transfer to the tissue, pair production requires energies well above diagnostic X-rays and is negligible, and while Compton scattering does deposit energy via recoil electrons, the scattered photons can escape the body, so the energy deposited per interaction is generally less than the full energy absorbed in a photoelectric event. Therefore, photoelectric absorption contributes the most to patient dose during diagnostic radiography.