1. Contribution from the ICIS − C.N.R., Corso Stati Uniti, 4, 35127 Padova, Italy, Laboratory of Nuclear Medicine, Department of Clinical and Experimental Medicine, University of Ferrara, Via L. Borsari, 46, 44100 Ferrara, Italy, Department of Pharmaceutical Sciences, University of Padova, Via Marzolo, 5, 35131 Padova, Italy, and ISTM − C.N.R., Via Marzolo, 1, 35131 Padova, Italy