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Background: The 153Sm-[tris(1,10-phenanthroline) Samarium(III)]complex (¹⁵³Sm-PL₃) was prepared in view of development of targeting therapeutic compounds for malignancies, and interesting in-vitro anti-tumor activities of lanthanide phenanthroline complexes,. Materials and Methods: Sm-153 chloride was obtained by thermal neutron flux (4 × 10¹³ n.cm^-2.s^-1) of enriched ¹⁵²Sm₂O₃ sample, dissolved in acidic media. The labeling was performed in ethanol in 24h, controlled by ITLC (1.0mM DTPA, pH.5, as mobile phase). The partition coefficient for the labeled compound was also determined. Results: A radiochemical yield of more than 95% was obtained. Radiochemical purity of 96% was obtained using ITLC with specific activity of about 27.75 GBq/mg. The radio-labeled complex was stable in aqueous solution at least 24 hours and no significant amount of free ¹⁵³Sm was released from the complex. The partition coefficient for the labeled compound was determined (log P. 3.4). The complex was stable in final formulation for 66h. The biological evaluation of the compound is under investigation. Conclusion: The radiolabeled compound used in this study was a very inexpensive and useful agent for the use as a therapeutic compound. Iran. J. Radiat. Res., 2012 10(1): 59-62

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Background: Therapeutic radiopharmaceuticals are designed to deliver high doses of radiation to selected target organs with an aim of minimizing unwanted radiation to surrounding healthy tissue. Due to the potential of targeted radiotherapy to treat a wide range of malignant conditions, [153Sm]-samarium maltolate was developed for possible therapeutic applications. Materials and Methods: The organ radiation-absorbed doses have been evaluated for human based on animal data. After intravenous administration of ¹⁵³Sm-Mal to four groups of rats, they were sacrificed at exact time intervals and the percentage of injected dose per gram of each organ was calculated by direct counting from rat data. Then S values for ¹⁵³Sm by using specific absorbed fractions were calculated. By taking advantage of the formulation that Medical Internal Radiation Dose suggests, radiation-absorbed doses for all organs were calculated and extrapolated from rat to human. Results: From rat data, it is estimated that a 185-MBq injection of ¹⁵³Sm-Mal into a human might result in the highest absorbed dose in the lymphoma tissues (liver 176.3, lungs 68, spleen 66.8 and sternum 19 mGy), especially in liver respect to the other tissues. Conclusion: These results suggest 153Sm-Mal as an efficiently new therapeutic agent in order to overcome possible lymphatic malignancies.