This book is written as both a text and a reference book. It contains numerous images from the biological sciences and clinical practice, tables, graphs, and fig ures, as well as exercises that are worked out to aid the reader in understanding principles or solving problems. In some cases, derivations are placed in appen dices so as not to break up the flow of the subject matter in the text. The book is intended for a broad audience interested in molecular imaging with positron emission tomography (PET). It is expected that the readers will range from undergraduate, graduate, and medical students to residents, physi cians, and scientists with backgrounds from various physical, biological, and medical specialty areas. Each chapter presents material in a straightforward man ner that is well illustrated and explained. Because of the diverse audience for the book, certain chapters or sections of chapters will be of more interest than oth ers to certain segments of the readership. Chapter 1 introduces the fundamental physics upon which PET imaging sys tems is based and discusses in detail the technologies and methods used to pro duce PET images. The chapter starts out by reviewing the physics of positron emission and annihilation and explains how positron range and photon non colinearity in coincidence detection place certain limits on spatial resolution.