How does the intensity of scattered radiation 1 m from the patient compare to the intensity of the useful beam at the patient's skin?

• A. Equal to the useful beam
• B. About 1/10% of the useful beam
• C. About 1/2% of the useful beam
• D. About 1% of the useful beam

Answer: (B)

The intensity of scattered radiation 1 meter from the patient is typically about 1/10% of the intensity of the useful beam at the patient's skin. This relationship arises from the principles of radiation dispersion and attenuation.

When an X-ray beam interacts with a patient's body, a portion of the radiation is absorbed, while some is scattered in various directions. The amount of scattering that occurs diminishes sharply with distance from the patient. At a distance of 1 meter from the patient, the intensity of the scattered radiation is significantly lower due to several contributing factors including the inverse square law, which states that the intensity of radiation decreases with the square of the distance from the source, and the natural attenuation of the scattered rays as they interact with the surrounding air and other materials.

This comparative measurement highlights the importance of shielding and safety protocols in radiography to minimize the exposure to scattered radiation, especially in areas where healthcare personnel may be present. Scattered radiation is inherently weaker than the primary beam, demonstrating effective radiographic practices to protect individuals from unnecessary exposure.