The long-awaited third edition of this classic text is here! The book is designed primarily as a useful reference for radiation oncology physicists, whether in training or established in their careers. The material is also intended to be accessible to radiation oncologists, dosimetrists, and radiation therapists who want a deeper understanding of the physical principles behind the technology they interact with on a daily basis. Unlike some other texts, this book does not skimp on many key concepts. As such, it is the book many practicing medical physicists pull when they want a detailed, but understandable explanation. The third edition is printed in full color to aid in understanding key imaging and treatment concepts. It includes an appendix with detailed answers to the many study questions asked at the end of chapters and it is also fully indexed.