Radioactive decay kinetics describes how activity changes over time. In nuclear medicine, accurate understanding of decay laws is essential for dose calculation, imaging timing, generator management, and radiation safety.

This section covers exponential decay, decay constants, half-life, mean life, and the mathematical relationship between activity and time. It also addresses physical half-life, biological half-life, and effective half-life. These are concepts central to radiopharmaceutical behaviour in vivo.

Exam questions frequently require calculation of remaining activity, comparison of isotopes with different half-lives, and interpretation of activity-time graphs. FRCR and ABR Core examinations commonly test both conceptual understanding and numerical problem-solving.

The questions in this section reinforce decay equations, graphical interpretation, and applied calculation scenarios relevant to clinical nuclear medicine practice.

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