If the gonads are properly shielded with 0.5 mm lead equivalent, approximately what percentage of the incident primary beam radiation dose can the gonads still receive from internal scatter?

• A. 5%
• B. 10%
• C. 20%
• D. 30%

Answer: (A)

Protective shielding reduces exposure not just to the direct beam but also to radiation that is scattered inside the patient. Internal scatter comes from interactions within tissues and, even with a shield in place, a small portion of that scattered energy can still reach the gonads. A 0.5 mm lead equivalent shield significantly attenuates those scatter photons, and the geometry of scatter plus the energy distribution at diagnostic x-ray levels means only a small fraction of the incident dose remains as gonadal exposure. In practical terms, this results in roughly 5% of the incident primary-beam dose reaching the gonads via internal scatter. The remaining options would imply less attenuation or a larger scatter fraction than is typical in standard shielding scenarios.