Described are methods and compositions for processes of preparing a radioactive solution of Sn-117m tetraiodide. Aspects include reacting a radioactive solid Sn containing Sn-117m with a solution of I2 in an organic solvent at a temperature and for a duration sufficient to result in the formation of Sn-117m tetraiodide. Then, the organic solvent is removed by evaporation to leave dry Sn-117m tetraiodide. The organic solvent is a low boiling point solvent capable of dissolving I2 and Sn tetraiodide. The organic solvent is selected from the group consisting of an alcohol and a chlorinated solvent. In embodiments may be selected from the group consisting of dichloromethane, trichloromethane, tetrachloromethane, or mixtures thereof. In embodiments, the organic solvent excludes alcohol. The I2 may be in a slight molar excess to the radioactive solid Sn. The method may further include distilling the reactants to remove excess I2 from the distillate.