Technetium-99m-labeled lymphocytes: a radiotoxicity study.

Radiolabeled white blood cells offer a unique clinical diagnostic technique. However, radiotoxicity to these radiosensitive cells must be carefully considered. Indium-111 has been shown to produce significant chromosomal alteration even at subscintigraphic doses. It has been suggested that 99mTc is less radiotoxic and may be desirable even though labeling is less efficient. The radiotoxicity of bound 99mTc was investigated in human lymphocytes by determination of division delay and chromosomal aberration as a function of increasing 99mTc activity concentration. This data revealed that human lymphocytes demonstrate significant division delay above 0.580 mCi/10(7) cells with chromosomal damage equivalent to 1 Gy of 250 keV x-ray at this level.