Which factor is NOT a determinant of internal radiation exposure?

Which factor is NOT a determinant of internal radiation exposure?

• A. The sites of deposition
• B. The route of entry into the body
• C. Its biological half-life
• D. Shielding from external sources

Answer: (D)

When evaluating internal radiation exposure, the key factors are how much radionuclide gets into the body and how it behaves inside. The amount and distribution determine which tissues receive dose, the route of entry affects where it tends to deposit, and the biological half-life tells you how long it stays in the body, controlling the duration of radiation exposure. Shielding from external sources, on the other hand, reduces dose from radiation outside the body and does not change the amount, location, or residence time of radionuclides that are already inside. So shielding from external sources is not a determinant of internal radiation exposure.

When evaluating internal radiation exposure, the key factors are how much radionuclide gets into the body and how it behaves inside. The amount and distribution determine which tissues receive dose, the route of entry affects where it tends to deposit, and the biological half-life tells you how long it stays in the body, controlling the duration of radiation exposure. Shielding from external sources, on the other hand, reduces dose from radiation outside the body and does not change the amount, location, or residence time of radionuclides that are already inside. So shielding from external sources is not a determinant of internal radiation exposure.