Measurement of red cell volume and splenic red cell pool using 113m indium

Using the lipophilic chelating agent, acetylacetone, red cells have been radiolabelled with the short-lived, generator-produced isotope, 113mIn. Following re-injection of these labelled cells, red cell volume has been measured and compared with corresponding values using 99mTc labelled red cells in 18 patients, and with 51Cr labelled red cells in five patients. 99mTc slightly overestimated red cell volume in relation to 113mIn, but 51Cr values were identical to 113mIn values. There was a close correlation between splenic red cell pool measured with 99mTc and with 113In. It was concluded that the intracellular stability and gamma emission of 113mIn make this isotope a superior alternative to 99mTc and 51Cr in measurements of red cell volume and splenic red cell pool.