Which statement best describes the relationship among primary, secondary, and scatter radiation?

• A. Primary radiation is produced at the cathode; Scatter radiation is the primary beam.
• B. Primary radiation is produced at the anode; Secondary radiation is produced when the primary beam interacts with matter; Scatter radiation is secondary radiation deflected from its original path.
• C. Secondary radiation is produced at the anode.
• D. Scatter radiation is produced only outside the body.

Answer: (B)

Primary radiation is produced at the anode in the x-ray tube and forms the useful beam that exits the tube toward the patient. When this primary beam interacts with matter, some photons are absorbed or cause other changes, and a portion of the emitted radiation becomes secondary radiation. Scatter radiation is a type of secondary radiation that is deflected from the photon’s original direction as it interacts with matter. This scattered portion travels in different directions and contributes to exposure outside the intended path. The other statements misidentify where the primary beam is generated, what secondary radiation is, or where scatter radiation originates, so they don’t fit as well.