Alteration of gallium distribution in the rat using periodically related elements: enhanced early imaging

Complexes of carrier-gallium and indium were administered to normal rats and rats with tumors 2 to 6 hours after an injection of carrier-free 67Ga citrate in order to determine their effect on the distribution of 67Ga. Both Ga and In rapidly and significantly decreased the blood activity. Imaging with the same dosage schedule showed decreased activity in soft tissue and viscera, and increased activity in bone, kidney, and bladder. In animals with tumor high doses of carrier-Ga were shown to deplete tumor activity as well as activity in viscera and soft tissues. Moderate doses of carrier-Ga allowed blood and soft tissue clearing with no significant loss of tumor activity. When In citrate was administered to animals with tumors 2 hours after administration of 67Ga, tumor activity continued to increase while soft tissue and visceral activity decreased. Simultaneous injection of In citrate and 67Ga drastically altered the distribution of 67Ga. Two hours after the injection activity was present only in the tumor, kidney, bladder, and bone. This rapid clearance of non-productive Ga brings forth the potential for use of short lived, positron emitting 68Ga coupled with emission tomography.