ABSTRACT
Megavoltage electron beams represent an important treatment modality in modern radiotherapy, often providing a unique option in treatment of superficial tumours. This chapter explores common questions and their solutions related to use of electron beams in radiotherapy. It explains the two types of stopping powers for electrons, namely the collision stopping power and radiative stopping power. The energy distribution of an electron beam varies with depth in a phantom. In a linear accelerator operating in electron mode, the X-ray target is removed from the electron beam path. Nevertheless, bremsstrahlung contamination exists in electron beam irradiation. The chapter then describes the different methods for collimating and beam shaping electron beams. The primary collimation of the electron beams is via the 'electron applicators' which are attached to the end of the collimator. The chapter also explains the characteristics of typical electron beam isodose curves.
