1 aNuclear Medicine Department bRenal Transplant Unit, Hospital Clínic, Barcelona, Spain cNuclear Medicine Department, Hospital and Biophysics Centre, University of Charles Mérieux, Lyon, France dCancer Imaging Department, Division of Imaging Sciences and Biomedical Engineering, King's College London, St Thomas' Hospital, London, UK eNuclear Medicine Department, Santa Maria della Misericordia Hospital, Rovigo, Italy.