Elution of '1lndium from reticuloendothelial cells

SUMMARY Measurement of isotope accumulation in an organ is often used to assess that organ's removal of blood cells labelled with the isotope. This technique is only valid if the isotope does not elute from the organ. Elution of "'In from the liver and spleen has been investigated in 14 subjects following intravenous injection of heat-damaged erythrocytes labelled with "'In. The elution rate from the spleen was found to be low, about 2 0 of the initial activity per day. The liver accumulated activity with respect to its initial uptake at a rate of about 50 % per day. Bone marrow was not visualised except in two patients in whom it was identifiable in the initial scan. The accumulation of isotope within an organ is often used as a measurement of uptake by that organ of blood cells previously labelled with the isotope. Examples of this are the accumulation of 51Cr in the spleen and liver, detected by surface counting, after injection of 51Cr-labelled erythrocytes, and the accumulation of "'In in the same organs, following injection of "'In-labelled platelets. The validity o