1. Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
2. Faculty of Psychology, Vita-Salute San Raffaele University, Milan, Italy.
3. Unit of Nuclear Medicine, Department of Diagnostic Imaging, N.O.P.—S. Stefano, U.S.L. Toscana Centro, Prato, Italy.
4. UFC Farmacotossicodipendenze, Department of Drug Addiction, N.O.P.—S. Stefano, U.S.L. Toscana Centro, Prato, Italy.
5. Department of Physics G. Occhialini, Università degli Studi di Milano Bicocca, Milan, Italy.
6. In Vivo Human Molecular and Structural Neuroimaging Unit, Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy.
7. Nuclear Medicine Unit, San Raffaele Hospital, Milan, Italy.