Chromium-Labeled Red Blood Cells

The use of 51Cr-labeled RBC's in nuclear medicine suggested the use of paramagnetic Cr(III)-labeled RBC's as an intravascular contrast agent for MRI. In dogs, significant enhancement of the liver and spleen is noted with minimal enhancement of the kidneys. The blood volume to be replaced with labeled RBC's in these studies corresponding to about one unit in humans. The survival half-life of labeled cells is 4.7 days compared to 16.6 days for unlabeled cells. Free Cr may contribute to the enhanced relaxation rates of the liver and spleen. Short term toxicity appears to be low, but further studies are necessary.