A unique class of radiopharmaceuticals labeled with the /sup 117m/Sn nuclide has been developed. The attractive properties of /sup 117m/Sn include a 14-day physical half-life and the emission of a single ..gamma..-photon with an optimal energy of 159 keV. A specialized apparatus was designed for the conversion of metallic /sup 117m/Sn to /sup 117m/SnCl/sub 4/ which was subsequently converted to a variety of useful /sup 117m/Sn-labeled organotin intermediates. The availability of this unique approach will now make possible the synthesis of a wide variety of /sup 117m/Sn-labeled compounds of biological interest. Such tissue-specific /sup 117m/Sn-labeled agents may represent a new class of useful radiopharmaceuticals. Continuing studies involving the preparation and testing of radiopharmaceuticals labeled with /sup 11/C, /sup 195m/Pt, and /sup 75/Se are also described. Several /sup 11/C-labeled amino acids including /sup 11/C-DL-tryptophan, /sup 11/C-1-aminocyclobutanecarboxylic acid (ACBC), and /sup 11/C-1-aminocyclopentanecarboxylic acid (ACPC) were prepared, and patient studies have demonstrated ACBC to be superior to ACPC for tumor localization. Studies with /sup 195m/Pt have recently been directed toward attempting to prepare high specific activity /sup 195m/Pt by the Szilard--Chalmers process. Progress is also reported in the development of an in vivo diffusion chamber assay technique that is being used to investigate …

Progress is reported for the applications of /sup 11/C, /sup 195m/Pt, /sup 75/Se, and /sup 123m/Te. Additional human clinical trials with /sup 11/C-DL-tryptophan and /sup 11/C-l-aminocyclobutane carboxylic acid have been completed. The modified Buecherer-Strecker amino acid synthesis has been used to prepare /sup 11/C-DL-phenylglycine and /sup 11/C-DL-phenylalanine. These two new /sup 11/C-labeled amino acids will be studied as potential tumor localizing agents. Preliminary studies concerning the comparative organ and subcellular distribution of /sup 195m/Pt-labeled cis- and trans- dichlorodiamineplatinum(II) have been completed. The results of in vivo studies have shown the cis isomer to bind to nuclear DNA to a significantly greater extent than the trans isomer. A series of /sup 123m/Te-labeled long-chain fatty acid analogs have been prepared as isosteres of unsaturated fatty acids. Several of these compounds show pronounced heart uptake in rats and may represent a new class of potential myocardial imaging agents. Studies on the preparation and tissue distribution of /sup 75/Se-..beta..-aminoethyl selenosulfate continue.