Which statement about the 5 cm proximity criterion is true?

• A. Shielding is recommended only if gonads are within 5 cm of the primary beam
• B. Shielding is never considered
• C. Shielding should be used regardless of diagnostic quality
• D. Shielding is only for pediatric patients

Answer: (A)

Gonadal shielding is used when the reproductive organs are close enough to the primary beam that their exposure could be significantly reduced without harming the diagnostic quality of the image. The 5 cm proximity rule states that if the gonads are within about 5 cm of the primary beam, shielding should be used to lower the patient’s radiation dose, as long as placing the shield does not obscure anatomy or degrade the image.

This is why the statement is the best answer: it captures the conditional nature of shielding—protect the gonads when they are within 5 cm of the beam, but not if shielding would interfere with the diagnostic information. Shielding is not universally required in every case (there is no blanket rule to shield regardless of distance), and it is not limited to pediatric patients. Also, shielding is not never considered; it is considered when proximity warrants it and when it won’t compromise the study.