The book bridges the gap between existing health physics textbooks and reference material needed by a practicing health physicist as the 21st century progresses. This material necessarily encompasses emerging radiation-generating technologies, advances in existing technology, and applications of existing technology to new areas. The book is written for advanced undergraduate and graduate science and engineering courses. It is also be a useful reference for scientists and engineers.The book bridges the gap between existing health physics textbooks and reference material needed by a practicing health physicist as the 21st century progresses. This material necessarily encompasses emerging radiation-generating technologies, advances in existing technology, and applications of existing technology to new areas. The book is written for advanced undergraduate and graduate science and engineering courses. It is also be a useful reference for scientists and engineers.