Which basic principles can be used to reduce radiation dose?

• A. time
• B. distance
• C. shielding
• D. all of the above

Answer: (D)

Reducing radiation dose hinges on three practical controls: time, distance, and shielding. Dose is proportional to how long you’re exposed, so shortening exposure time—using techniques like pulsed fluoroscopy or minimizing unnecessary imaging—directly lowers the amount of radiation you receive. Distance matters because radiation intensity drops off quickly as you move away from the source; increasing your distance or using remote controls keeps you farther from the beam, cutting exposure dramatically (the dose roughly falls off with the square of the distance). Shielding provides a barrier between you and the radiation, with lead or equivalent materials absorbing a portion of the beam and protecting you and others in the room.

When you combine these approaches—putting the shortest necessary exposure time into practice, maximizing distance from the source whenever feasible, and using appropriate shielding—you achieve the greatest reduction in dose. That’s why all of the above is the best answer.