Which of the following interactions represents the highest contribution to occupational exposure during a radiographic procedure?

• A. Photoelectric Absorption
• B. Compton Scatter
• C. Coherent Scatter
• D. Pair Production

Answer: (B)

Compton scattering is the main source of occupational exposure in diagnostic radiography. When x-ray photons pass through the patient, many interact by ejecting electrons and producing scattered photons that change direction. These scattered photons exit the patient and travel in various directions, some toward the radiographer and other staff. Because this scattered radiation is what reaches people outside the primary beam, it becomes the dominant contributor to dose outside the patient.

Photoelectric absorption, while important for patient dose and image contrast, involves photons being absorbed in tissue rather than scattered, so it doesn’t add as much to staff exposure. Coherent (Rayleigh) scattering has very low probability at diagnostic energies and transfers little energy, contributing negligibly. Pair production requires photon energies above 1.022 MeV and is not a factor in typical diagnostic radiography, so it also has minimal impact on occupational exposure.