Accidental ingestion of Tc-99m in breast milk by a 10-week-old child.

Ten weeks after the birth of her first child by Caesarian section, a 27-year-old woman was admitted for evaluation of a possible central nervous system lesion. Four hours after i.v. administration of 15 mCi of Tc-99m for a brain scan, the patient breast-fed her infant; then became concerned about the possibility of radioactivity in her breast milk. Total body gamma-ray measurements of the infant indicated ingestion of 82.5 muCi Tc-99m (corrected for effective T 1/2), while ingestion calculated from gamma-ray measurements of serial milk samples was 75.6 muCi. The single organ radiation dose for the thyroid as the critical organ was 300 mRad, whereas that to the total body was 12 mRad (values derived from 82.5 muCi determined by whole body counting). Had breast feeding been continued at 4-hr intervals, the total ingested activity would have been 94.8 muCi giving the infant a dose of 380 mRad to the thyroid and 16 mRad to the whole body. Had the feeding been given 1/2-hr after injection 726 muCi would have been ingested, increasing the dose by a factor of 10.