The combined use of iron 52 and its contaminant iron 55 in studies of the bone marrow.

A liquid scintillation counting technique has been used to measure 55Fe incorporation into red blood cells with counting efficiencies of the order of 10% for 0.1 ml whole blood. Measurements have been carried out over a period of two weeks following the intravenous administration of the shortlived cyclotron produced 52Fe which contains 55Fe (half-life 2.6 years) as contaminant. 52Fe, with its short half-life of 8.2 hours and suitable gamma-ray emissions, is the isotope of choice for bone marrow imaging and short term ferrokinetic studies such as plasma clearance and early organ uptake of iron. However, long term iron utilization cannot be measured with this radionuclide alone. By exploiting the presence of 55Fe this limitation has now been overcome.