Book excerpt: Linear Accelerators for Radiation Therapy, Second Edition focuses on the fundamentals of accelerator systems, explaining the underlying physics and the different features of these systems. This edition includes expanded sections on the treatment head, on x-ray production via multileaf and dynamic collimation for the production of wedged and other intensity modulated beams, on electron scattering systems, and on dosimetry. With high-quality illustrations and practical examples throughout, it contains a detailed description of electron beam optics and linear accelerator components. The final chapter explains how to use other equipment, such as scanners and simulators, in conjunction with linear accelerators for optimum treatment of cancers.