Welcome back to the RadOnc Smart Review Physics Series! In P12b, we defined the crucial ICRU target volumes (GTV, CTV, PTV). Now, how do we deliver dose that conforms tightly to those volumes, especially when they're complex shapes wrapped around sensitive organs? In Episode P13a: Intensity Modulated Therapy (IMRT & VMAT Principles, QA), we explore the sophisticated techniques of IMRT and VMAT that allow us to "dose paint" with remarkable precision, and the essential QA needed to ensure they work as planned.