Which of the following statements is true regarding gonad dose when shielding is used and internal scatter is present?

• A. The gonads receive 0% of the incident primary beam
• B. The gonads can still receive about 5% of the incident dose
• C. The gonads receive more than 50% of the incident dose
• D. Shielding eliminates all dose to the gonads

Answer: (B)

Shielding lowers gonadal exposure but cannot make it zero because radiation is produced inside the patient and can scatter to the gonads, as well as some secondary radiation can leak around the shield. Blocking the primary beam with a lead shield drastically reduces dose, but a small fraction still gets through due to internal scatter. In typical scenarios, this residual dose is about 5% of what the gonads would receive from the primary beam if there were no shielding. This reflects the balance between effective attenuation of the direct beam and unavoidable scatter reaching the gonads.