Nuclear equations and half-lives

Explain — 4 marks

A hospital uses Technetium-99m (Tc-99m) as a radioactive tracer in medical imaging. Tc-99m has a half-life of 6 hours. A patient is injected with an initial activity of 800 MBq at 09:00. The medical team needs to understand how the activity changes over time to plan when scans should be performed and when it is safe to discharge the patient.

1. Define what is meant by the half-life of a radioactive isotope. [1 mark]
2. Calculate the activity of Tc-99m remaining in the patient's body at 21:00 (12 hours later). Show your working. [2 marks]
3. Explain why Tc-99m is suitable for use as a medical tracer, considering its half-life and the type of radiation it emits (Tc-99m undergoes gamma decay). [1 mark]