Welcome back to Radiation Oncology Smart Review – the targeted prep for your radiation oncology boards! I’m your guide, diving deep into the calculations that matter. This is Episode 17a of our Calculation Toolkit series, titled Radiation Oncology Calculations 1: Half-Lives and Seed Sleuths. Today we’ll master three bread-and-butter RAPHEX problem families: first, radioactive decay and time-activity puzzles, second, effective half-life mash-ups, and third, permanent implant total-dose questions. By the end you’ll know why lambda keeps physicists up at night, how to find the Goldilocks half-life combining body and physics, and how one sleepy iodine one twenty-five seed still manages to deliver its full punch over months.