The updated edition of the third of three vollumes on Medical Physics presents modern physical methods for medical therapy with a focus on tumor treatment. It provides background information on radiation biology, radiation response of tissues, and linear energy transfer through radiation. Therapies with external radiation sources (x-rays, protons, neutrons) as well as internal radiation sources (brachytherapy) are discussed in detail. Other chapters deal with the use of lasers and nanoparticles in modern medicine. This volume closes with a short chapter on medical statistics. NEW: highlighted boxes emphasize specifi c topics; math boxes explain more advanced mathematical issues; each chapter concludes with a summary of the key concepts, questions, exercises, and a self-assessment of the acquired competence. The appendix provides answers to questions and solutions to exercises.