TECHNETIUM-LABELED RED BLOOD CELLS.

Labeled red cells are used in red blood-cell mass determinations, red-cell survival studies, placental localization, and spleen scanning. Chromium-5 1, which is presently used to label the cells, does not possess the favorable physical characteristics that technetium does for certain applications. Therefore, if technetium could be incorporated in red blood cells, a more valuable tracer would be available. However, some technical difficulties have been en countered in past attempts to label erythrocytes with BOmTc