Distribution and dosimetry of 111In-labeled platelets

The distribution of 111In-labeled platelets was studied in five young, healthy men. The radioactivity in the lungs, heart, liver, spleen, kidneys, and testes was determined from areas-of-interest in computed gamma-camera scans at intervals up to 75 hours after injection. After the first four hours, the activity in each organ studied except the liver and kidney decreased at roughly the physical decay rate. In the liver and kidney, the curves were relatively flat, indicating continued accumulation of the radiotracer. The calculated mean radiation absorbed dose per unit administered activity was 0.60 +/- 0.07 rad/mCi (0.16 +/- 0.02 Gy/GBq) for the total body, and was 34 +/- 6 rad/mCi (9.0 +/- 1.5 Gy/GBq) for the spleen.