This fourth edition of the classic textbook has been updated and revised by a renowned team of experienced health physicists and book authors, to include current physiokinetic and dosimetric models as recommended by the International Commission on Radiological Protection. In addition, all units are now given using the SI system, making the book even more useful to an international audience, while the sections on statistics have been completely rewritten to make them more accessible. As a result, the text offers advanced students and professionals comprehensive coverage of the major concepts behind the origins and transport of ionizing radiation in matter. It covers the detection and measurement of radiation and the statistical interpretation of the data, thoroughly describing the procedures that are used to protect humans and the environment from the potential harmful effects. Throughout, the basic principles are elucidated using numerous worked examples that exemplify practical applications and each chapter includes problem sets (with partial answers) and extensive tables and graphs for continued use as a reference work.