Welcome back to Radiation Oncology Smart Review – Episode 17 part B: Dosimetry Detectives and Chamber Charades. Last time, we tackled the ticking clocks of decay and permanent implants. Today, we put on our detective hats to investigate how we actually measure radiation and make sure the right dose goes to the right place. We’ll decode the secrets of ion chambers and their sneaky temperature-pressure dependence, master the Monitor Unit, or M U, calculations for both S A D and S S D setups – the absolute bedrock of clinical physics – figure out how dose changes with depth using P D Ds and T M Rs, and learn how linacs play geometric tricks with field sizes.