Dose-dependent change in tissue uptake of 17 beta-(16 alpha-[125I]iodo)-estradiol in female rats: application to external imaging of mammary carcinoma.

Recently, many studies have drawn attention to the possibility of imaging estrogen-receptor-positive breast cancer with a high-affinity ligand such as 17 beta-(16 alpha-[125I]iodo)-estradiol (I-E2). We tried to determine the most suitable time and dose for imaging with this compound, using uteri of mature Sprague-Dawley rats. Although the uptake of I-E2 in the target organ (uterus) reached its peak 1 h after subcutaneous injection, the ratio of uptake in the target organ to that in nontarget organs (lung and muscle) peaked at 4 h. We also found that this ratio decreased as the dose increased. The clearest image was available 4 h after the dose meeting the minimum requirement for imaging was administered. An imaging trial of dimethylbenzanthracene (DMBA)-induced mammary carcinoma is also demonstrated.