1. Department of Medical Physics, School of Medicine, University of Patras, Rion, Greece.
2. National Center of Scientific Research “Demokritos,” Institute for Nuclear and Radiological Sciences, Technology, Energy and Safety, Athens, Greece.
3. Department of Biomedical Technology Engineering, TEI of Athens, Athens, Greece.
4. Department of Radiology, School of Medicine, University of Patras, Rion, Greece.
5. Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.