Which method specifically reduces peak skin dose by limiting the beam to the smallest necessary area?

• A. Collimation
• B. Shielding
• C. Distance
• D. Dose rate limits

Answer: (A)

Limiting the beam to the smallest area needed directly reduces the amount of tissue exposed and the amount of scatter produced. Collimation shapes and confines the x-ray beam to the region of interest, so only the necessary skin area is irradiated. With less tissue being irradiated and less scatter generated, the highest dose that skin receives—the peak skin dose—also decreases.

Shielding protects specific organs but doesn’t change the size of the beam or the amount of scatter produced within the irradiated field. Distance reduces dose to some extent via the inverse square law, but it doesn’t directly limit the area irradiated on the skin for a given projection. Dose rate limits control how fast dose is delivered, not the field size.