LABELED TRANSFERRINS FOR TUMOR AND ABSCESS IMAGING

Abstract

The uptake and imaging properties of labeled transferrins (TF) was compared to Ga-67-citrate in abscess-bearing rats, rabbits, and tumor bearing mice. Ru-97 or Ru-103 TF and Ga-67 TF were prepared by the nitrilotriacetic acid method. All radiopharmaceuticals were injected intravenously and tissues assayed at 2,4,5,6, and 24 hours. Organs were weighed and counted in a NaI(T1) well-counter. Data were expressed as percent dose per gram or organ. New Zealand rabbits with turpentine-induced abscesses were imaged using a gamma camera with energy collimator. The absolute tumor concentrations of Ga-67-citrate were similar to Ru-103 TF, but Ru-97 TF concentrated twice as much in the tumor (probably due to radionuclidic impurity of Ru-103). No significant differences were observed in the abscess uptake of labeled TF and Ga-67-citrate. The blood levels of the labeled TF were twice as much as Ga-67-citrate at all time intervals, however, the muscle uptake was lower. For these reasons tumor/blood and abscess to blood ratios were higher for Ga-67-citrate, but tumor/muscle and abscess/muscle were higher for TF. Moreover, in the abscess-bearing rabbits it was possible to visualize the lesion at 0.5 hr after injection. The optimal time for abscess visualization was 3 hours. The administration of desferal did not affect the distribution of Ru-97-TF. These data support the hypothesis that the active pharmacological form involved in tumor and abscess uptake is the metal-TF complex and that administration of pre-labeled TF may enable early visualization of neoplasms and focal inflammatory lesions in areas with low vasculature. Research carried out under the auspices of the U.S. Dept. of Energy under Contract No, DE-AC02–76CH00016.