
Answer
Radiation Dose Equivalence – Tc-99m Beta vs Gamma & Effect of Mass
🔹 Part G: Beta Ray vs Gamma Ray (Same Energy)
The equivalent dose depends on the type of radiation and its biological effect. The radiation weighting factor (WR) differs for various radiation types:
- Gamma rays: WR = 1
- Beta particles: WR = 1
For beta and gamma rays of the same energy, the biological damage per unit absorbed dose is nearly the same because they both are low linear energy transfer (LET) radiations. Therefore, the equivalent dose would remain similar, and any change would be small and negligible.
✔ Correct Answer: The equivalent dose would go up by a small factor.
🔹 Part H: Effect of Mass on Dose Received
The equivalent dose is calculated as:
If the same amount of radioactive material is administered to a smaller animal (e.g., a dog of 2 kg compared to a human of ~80 kg), the absorbed energy is spread over a much smaller mass, leading to a significantly higher dose.
Assuming the human mass is 80 kg:
✔ Correct Answer: The equivalent dose would increase by a factor of 40.
