and

Iron-59 has been used for a number of years and 52Fe more recently for haemalogical studies involving the bone marrow and erythropoiesia. The long halflife of Fe allows iron incorporation and long-term blood loss to be studied. However, organ imaging with this radionuclide is difficult because of the higenergy gamma emission. The short halflife of the cyclotron-produced positron emitter Fe allows much higher activities to be ministered and also pduces a more clearly resolved image than that obtained with Fe. For this reason Fe has been used for marrow imaging and short-term plasma clearance studies. A problem asciated with the use of 521e in this way is the uncertainty about the te of t mMfl daughter. A decay schema showing the major pathways for both Fe and Mn is shown in Fig. 1. Iron-52 decays by electron capture and positron 8.2