1. Department of Nuclear Medicine‑PET/CT, General Hospital of Athens ‘Evaggelismos’, 10676 Athens, Greece
2. Research Center of Mathematics, Academy of Athens, 11527 Athens, Greece
3. Institute for Nuclear and Radiological Sciences and Technology, Energy and Safety, National Center for Scientific Research ‘Demokritos’, 15310 Athens, Greece
4. Center for Gamma‑Ray Imaging, Department of Medical Imaging, University of Arizona, Tucson, AZ 85724, USA