This book, now in its fourth edition, is unique in detailing in depth the technological basis of radiation therapy. Compared with the previous edition, all chapters have been rewritten and updated. In addition, new chapters have been included on various topics, including the use of imaging in treatment planning, second malignant neoplasms due to irradiation, and quality assurance in radiation oncology. The book is divided into two sections. The first covers basic concepts in treatment planning, including essential physics, and explains the various approaches to radiation therapy, such as intensity-modulated radiation therapy, tomotherapy, and high and low dose rate brachytherapy. The second part documents the practical clinical applications of these concepts in the treatment of different cancers. All of the chapters have been written by leaders in this field. This book will provide an invaluable guide to the basic technological factors and approaches in radiation therapy.