INTRATUMOR injection of radioactive colloidal gold as a means of sharply localizing radiation within tumors was proposed in 1947 by P. F. Hahn.1 Perhaps the main reason that widespread clinical use has not yet been made of this form of therapy is the technical difficulty of (1) insuring an even dispersion of the radioactive solution throughout the tumor, and (2) preventing the therapist from receiving hazardous amounts of radiation when he is working with high levels of activity. These technical problems can largely be overcome by use of the special equipment and techniques which are described in this paper.
PHYSICAL PROPERTIES OF AU198
Au198 is produced from the stable isotope Au197 by neutron bombardment in the chain-reacting pile at Oak Ridge. Since Au197 has a high cross section capture for neutrons (100 barns), the production of Au198 is reasonably efficient, and a high specific activity