Octreotide labeled with~(99)Tc~m-for detecting somatostatin receptor positive tumors: preparation, identification and preliminary clinical application

Objective To develop an optimal method to label octreotide with 99 Tc m directly and evaluate characteristics of receptor mediated binding of 99 Tc m octreotide in vitro and its potential as an imaging agent of somatostatin receptor positive tumors Methods Sodium ascorbate and Na 2S 2O 4 were adopted to label octreotide with 99 Tc m; cell membrane of Wistar rat brain cortex on which there are numerous somatostatin receptors was used for radioreceptor assay in vitro; radioactivity biodistribution assay and clinical somatostatin receptor imaging were performed Results The yield of 99 Tc m octreotide was 78 5%, radiochemical purity was 93 8% after purification The 99 Tc m octreotide compound remained stable after at least 4 h at room temperature Wistar rat brain cortex cell membrane receptor binding showed significant features associated with receptor mediated binding Satisfactory 99 Tc m octreotide receptor images were obtained in 3 lung cancer cases Conclusions These results suggest that 99 Tc m octreotide is a promising radiopharmaceutical for scintigraphic imaging of tumors rich in somatostatin receptors