In Vivo internal dosimetry is defined as?

• A. Direct measurement of radiation emitted from the body from internally deposited radionuclides.
• B. Measurement of RAM exterior to the body, excreted or removed.
• C. Absorbed dose to the head, neck, and thyroid.
• D. Dose to the lens of the eye from external exposure.

Answer: (A)

In vivo internal dosimetry is the direct measurement of radiation emitted from the body by radionuclides that have deposited inside the body. This means using detectors placed on or around the person to pick up photons or particles emitted by radionuclides located inside, providing a direct estimate of the internal radiological burden and the resulting absorbed dose. This approach is different from measuring material outside the body that has been excreted or removed (which infers internal contamination indirectly) and from focusing on radiation incident to specific outside regions or from external exposure. The key idea is capturing the actual emissions from inside the body to quantify the dose, which is exactly what the definition describes.