Where does scatter radiation originate?

• A. From the tube housing
• B. From the viewer screen
• C. Within the patient or imaging objects
• D. From the room walls

Answer: (C)

Scatter radiation comes from interactions of the primary X-ray beam with matter, most often within the patient or imaging object. When the beam hits tissues, photons can undergo Compton scattering, changing direction and exiting the body as scattered photons. These exit photons contribute to image fog and increase dose to anyone nearby. The tube housing is the source of the primary beam, not scatter, and the viewer screen is a detector, not a source of radiation. Room walls can reflect some scattered photons, but they are not the origin; the dominant source is the tissue interactions inside the patient.