The radiotracer (99m)Tc-MIBI is not genotoxic for human peripheral blood lymphocytes at diagnostic radioactive dose.

The radiotracer technetium-99m methoxyisobutyl isonitrile ((99m)Tc-MIBI) has been widely used for myocardial blood flow imaging. We investigated the genotoxicity of (99m)Tc-MIBI in cultured human lymphocytes at the same concentration used in patients. Radioactivity doses were determined in whole blood at 5 min post-injection of 20 mCi (99m)Tc-MIBI in patients. Subsequently, whole blood of human volunteers was incubated with 1, 2.3, 4 or 8 microCi (99m)Tc-MIBI. After a 30-min incubation, the lymphocytes were stimulated with a mitogen to assay for micronuclei in cytokinesis-blocked binucleated cells. The frequency of micronuclei in samples treated with this radiopharmaceutical up to 2-fold (8 microCi) the concentration of (99m)Tc-MIBI normally found in the blood of patients was not more than in control lymphocyte cultures. We concluded that there is no increased induction of micronuclei in lymphocytes incubated with (99m)Tc-MIBI at the radioactivity doses used for diagnostic purposes.