1. Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
2. Medical Faculty, Trakia University, 11 Armeiska Str., Stara Zagora 6000, Bulgaria
3. Institute of Biophysics
and Biomedical Engineering, Bulgarian Academy of Sciences, 23 Avad.
G. Bonchev Str., Sofia 1000, Bulgaria
4. Medical Faculty, Sofia University, 1 Koziak Str., Sofia 1407, Bulgaria