Scattered radiation coming from the patient, compared to the primary incident radiation, is:

• A. Less energetic
• B. Equally energetic
• C. More energetic
• D. None of the above

Answer: (A)

Scattered radiation from the patient is less energetic than the primary incident radiation. In diagnostic radiology, the main interaction that creates scatter is Compton scattering, where the incoming photon transfers some of its energy to a recoil electron while changing direction. Because energy is conserved, the scattered photon exits with less energy than the incident photon, with the amount of loss depending on the scattering angle—the larger the angle, the more energy is lost. Coherent (Rayleigh) scattering can occur with little to no energy change, but it is much less likely at diagnostic energies, so it does not change the overall conclusion.