Which of the following is considered secondary radiation?

• A. Primary beam
• B. Scatter radiation
• C. Leakage radiation from the x-ray tube head
• D. Cosmic radiation

Answer: (B)

Secondary radiation is radiation produced when the primary beam interacts with matter, such as patient tissues. Scatter radiation is the classic example: photons from the primary beam strike the body, undergo scattering (often Compton interactions), and are deflected in new directions. These deflected photons exit the patient and can expose the operator and others, which is why shielding and proper technique are important. The primary beam is the original photons before any interaction. Leakage radiation originates from the x-ray tube housing and escapes without interacting with patient tissue, so it’s not considered secondary radiation. Cosmic radiation is natural background radiation unrelated to the imaging process.