The aim of intensity modulated radiation therapy (IMRT) is to kill tumor cells while at the same time protecting the surrounding tissue and organs from the damaging effect of radiation. Given the number of beams and beam directions, beam intensity optimization needs to determine beam intensity profiles that yield the best dose distribution under consideration of clinical and physical constraints. In this book, we first review existing mathematical models and computation methods for the beam intensity optimization problem. Then we formulate the beam intensity optimization problem ...