title: Preface.
authors.affiliation: Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva, Switzerland. Electronic address: habib.zaidi@hcuge.ch.
authors.forename: Habib
authors.initials: H
authors.lastname: Zaidi
authors.affiliation: Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA. Electronic address: abass.alavi@uphs.upenn.edu.
authors.forename: Abass
authors.initials: A
authors.lastname: Alavi