Which of the following is NOT listed as a factor affecting the quantity of scattered radiation?

• A. kVp
• B. Field Size
• C. Part Thickness
• D. Film Speed

Answer: (D)

The amount of scattered radiation produced during an exposure depends on three main influences: the beam energy, the size of the area being irradiated, and the thickness or density of the part. Higher kVp means more photons have enough energy to undergo scattering interactions (like Compton scattering), so scatter increases with higher beam energy. Wider field size irradiates more tissue, producing more opportunities for scatter. A thicker or denser part provides more tissue for interactions, also boosting scatter production.

Film speed, by contrast, is a characteristic of the imaging receptor system—the sensitivity of the film-screen or digital detector to recorded exposure. It affects how the image appears and the dose required for a given image, but it does not change how many scatter photons are generated in the patient. Therefore, film speed is not a factor that affects the quantity of scattered radiation.