Development of positron emitting radionuclides for imaging with improved positron detectors

Recent advances in positron cameras and positron ring detectors for transverse section reconstruction have created renewed interest in positron emitting radionuclides. This paper reports on: generator-produced 82Rb; cyclotron-produced 62Zn; and reactor-produced 64Cu. Investigation of the 82Sr (25 d)--82Rb (75 s) generator determined the elution characteristics for Bio-Rex 70, a weakly acidic carboxylic cation exchanger, using 2% NaCl as the eluent. The yield of 82Rb and the breakthrough of 82Sr were determined for newly prepared columns and for long term elution conditions. Spallation-produced 82Sr was used to charge a compact 82Rb generator to obtain multi-millicurie amounts of 82Rb for myocardial imaging. Zinc accumulates in the islet cells of the pancreas and in the prostate. Zinc-62 was produced by protons on Cu foil and separated by column chromatography. Zinc-62 was administered as the amino acid chelates and as the ZnCl2 to tumor and normal animals. Tissue distribution was determined for various times after intravenous injection. Pancreas-liver images of 62Zn-histidine uptake were obtained in animals with the gamma camera and the liver uptake of /sup 99m/Tc sulfur colloid was computer subtracted to image the pancreas alone. The positron camera imaged uptake of 62Zn-histidine in the prostate of a dog at 20 h. 64Cu was chelated to asparagine, a requirement of leukemic cells, and administered to lymphoma mice. Uptake in tumor and various tissues was determined and compared with the uptake of 67Ga citrate under the same conditions. 64Cu-asparagine had better tumor-to-soft tissue ratios than 67Ga-citrate