Which of the following would NOT increase patient dose?

• A. Increasing mAs
• B. Increasing SID
• C. Increasing exposure time
• D. Increasing kVp

Answer: (B)

Distance from the X-ray source directly affects how much radiation the patient absorbs. The dose falls off with the square of the distance, so increasing the source-to-image distance spreads the beam and lowers the skin dose for the same beam intensity. That’s why increasing SID would not increase patient dose; it reduces it.

Increasing mA or the exposure time both raise the total number of photons produced, delivering more energy to the patient and increasing dose. Increasing kVp raises the energy of the photons, increasing beam penetration and energy deposited in tissue, which also tends to raise patient dose.