Adriaan A Lammertsma1,2. 1. Medical Imaging Center, Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. aa.lammertsma@amsterdamumc.nl. 2. Department of Radiology and Nuclear Medicine, Amsterdam UMC, Vrije Universiteit, Amsterdam, The Netherlands. aa.lammertsma@amsterdamumc.nl.