This book is designed to give the reader a solid understanding of the physics and instrumentation aspects of PET, including how PET data are collected and formed into an image. Topics include basic physics, detector technology used in modern PET scanners, data acquisition, and 3D reconstruction. A variety of modern PET imaging systems are also discussed, including those designed for clinical services and research, as well as small-animal imaging. Methods for evaluating the performance of these systems are also outlined.