Metabolic dissociation of short-lived barium-137m from its cesium-137 parent.

At 4 to 7 days after Cs(137) administration, Ba(137m) was found to exceed Cs(137)-Ba(137m) equilibrium proportions in bone and plasma by factors of 3 and 14, respectively, in the living animal. This demonstrated the in vivo escape of Ba(137m) from sites of Cs(137) accumulation. Liver tissue was slightly deficient in Ba(137m), whereas tissues such as bone marrow and spleen showed little or no deviation from equilibrium.