What is the percentage intensity of scattered radiation perpendicular to and 1 m from the patient, compared to the useful beam at the patient's surface?

The intensity of scattered radiation can vary based on several factors, including the type of imaging or therapeutic procedure, the energy of the radiation, and the distance from the patient. Typically, scattered radiation at a distance of 1 meter from the patient is significantly less compared to the intensity of the useful beam at the patient's surface.

In this context, the percentage intensity of scattered radiation is generally considered to be very low, reflecting the fact that most of the useful beam's energy is deposited at the surface and diminishes quickly with distance. Research and guidelines in radiological safety indicate that at 1 meter from the patient, scattered radiation typically amounts to about 0.1% of the original useful beam intensity. This low percentage underscores the effectiveness of decreasing radiation exposure with distance, as well as the nature of scattering as it occurs in soft tissue or other materials.

This makes the option indicating 0.1% the correct answer, as it aligns closely with the established principles of radiation safety and the behavior of radiation as it scatters away from the primary beam.