Which statement is true about field size and scattered radiation?

• A. Increasing field size decreases scattered radiation
• B. Field size has no effect on scattered radiation
• C. Larger field size increases scattered radiation
• D. Field size only affects patient dose, not scatter

Answer: (C)

Scatter radiation comes from photons that interact with tissue inside the patient. The amount of scatter depends on the volume of tissue exposed to the primary beam. When field size increases, more tissue is irradiated, which raises the number of Compton interactions and sends more scattered photons toward the image receptor. This extra scatter degrades image contrast and contributes to patient dose as well. So larger field sizes increase scattered radiation, while tighter collimation reduces scatter and improves image quality.