Welcome back to Rad Onc Smart Review, the podcast that helps you master the core concepts of radiation oncology and radiobiology. This is Episode 12 Part A, Cell Cycle Kinetics - Phases & Measurement. In our previous episodes, we've explored how tumors grow and respond to their microenvironment, including the crucial role of hypoxia and angiogenesis. Today, we're diving into the engine that drives cell growth and division: the cell cycle. We'll review its phases, discuss how radiosensitivity changes as cells progress through these phases, and explore key laboratory techniques used to measure and analyze cell cycle kinetics.