Chapter 12: Photon Beam Treatment Planning: Part I

The previous chapters presented methods for calculating doses to a point. While this is useful for learning purposes, modern clinical practice often requires not just a calculation of dose to a single point but a calculation of dose to an entire 3D volume. This is accomplished with a “treatment planning system” (TPS), i.e., a computer software package used to create plans and calculate dose in 3D space. TPS systems most often use a CT scan acquired at the time of “simulation,” which is typically several days before treatment starts. This chapter will explore treatment planning, the associated dose calculation methods, and techniques that are frequently employed to achieve high-quality plans. Much of the discussion here also applies to software that performs secondary dose calculations. Secondary dose calculation systems are commonly used in radiation therapy as a second, independent check of dose for each treatment plan.