Drew A. Torigian, MD, MA, FSAR 
Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA
Andreas Kjær, MD, PhD, DMSc 
Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging, Rigshospitalet and University of Copenhagen, KF-4012, Blegdamsvej 9, 2100 Copenhagen, Denmark
Habib Zaidi, PhD, PD 
Division of Nuclear Medicine & Molecular Imaging, Geneva University Hospital, CH-1211 Geneva, Switzerland
Abass Alavi, MD, MD (Hon), PhD (Hon), DSc (Hon) 
Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA