1. Turku PET Centre (L.S., V.O., K.H., N.S., J.K., P.N., P.I.) FIN-20521 Turku, Finland
2. Department of Medicine (P.N.), University of Turku, FIN-20521 Turku, Finland
3. Institute of Clinical Physiology (P.I.), CNR National Research Council, 56124 Pisa, Italy