1. In Vivo Cellular and Molecular Imaging Laboratory (ICMI), Vrije Universiteit Brussel, Brussels 1090, Belgium
2. Institute for Nuclear Materials Science, Belgian Nuclear Research Center (SCK·CEN), Mol 2400, Belgium
3. Department of Radiation Physics, Sahlgrenska Academy, University of Gothenburg, Gothenburg SE-413 45, Sweden
4. The PET and Cyclotron Unit, KF3982, Copenhagen University Hospital, Copenhagen 2100, Denmark
5. Nuclear Medicine Department, Universitair Ziekenhuis Brussel (UZ Brussel), Brussels 1090, Belgium