How far from a patient should we be to minimise scattered radiation?

• A. 1 metre
• B. 3 metres
• C. 2 metres
• D. 5 metres

Answer: (C)

The key idea is that scattered radiation from a patient drops off quickly as you move away. When X-rays pass through tissue, some photons scatter in all directions, creating a secondary source of radiation that can reach the operator. The intensity of this scatter decreases with distance roughly according to the inverse square law: if you double the distance, the exposure from scatter is reduced to about a quarter.

Being at a practical distance helps keep exposure low while you position and take the radiograph. Standing about two metres away from the patient provides a good balance between safety and being able to work effectively. It significantly lowers scatter exposure compared with being closer, and it’s a commonly recommended stand-off distance when you don’t have a shielding barrier in place.

Of course, using protective barriers (lead screens, aprons, thyroid shields) and minimizing exposure time are also essential parts of minimizing dose. Being farther away beyond two metres offers even less scatter, but in real settings, two metres is a practical and effective standard to maintain safety while still performing the procedure efficiently.