Biodistribution of radioactivity in tumor, blood, and normal organs of athymic mice bearing Ramos xenografts injected with either 1F5 or HB8181 Abs directly labeled with ²¹³Bi. Groups of 5 mice were injected with 1.4nM either conventional trace-labeled 1F5 or HB8181 Abs. Mice were euthanized 10, 45, 90, and 180 minutes after injection of each ²¹³Bi-labeled Abs. The radioactivity in tumor, blood, and normal organs were quantified by gamma counting, corrected for decay, and expressed as the % ID/g of tissue.