Which interaction is most associated with scatter radiation reaching the operator?

• A. Photoelectric effect
• B. Compton effect
• C. Coherent scattering
• D. Pair production

Answer: (B)

The key idea is why scattered photons reach the operator in diagnostic X-ray work. In this energy range, photons most often interact with tissue by Compton scattering, where a photon transfers part of its energy to an outer electron and is deflected in a new direction. The scattered photon remains energetic enough to escape the patient and travel toward the operator, especially if shielding or distance isn’t enough to block it. This makes Compton scattering the primary source of occupational exposure from scatter.

In contrast, photoelectric absorption mostly removes photons within the patient and doesn’t produce a scattered photon that can reach the operator. Coherent (Rayleigh) scattering does occur but contributes much less to operator dose because it involves minimal energy transfer and often results in photons that don’t escape in directions toward the clinician. Pair production requires photon energies well above diagnostic levels and is not a major factor in typical radiography.

So, scattering reaching the operator is most closely linked to Compton scattering.