Cyclotron based production of high specific activity [^197(m)Hg]HgCl₂

^197mHg (T_1/2 = 23.8 h, E_γ 133.98 keV, 33.5%) and ¹⁹⁷Hg (T_1/2 = 64.14 h, E_γ 77.4 keV, 18.7%) are gamma-emitting radionuclides suitable for SPECT imaging and of additional interest because of the potential therapeutic us of their Auger- and conversion electron emission. The unique chemical and physical properties as metal which forms water-stable carbon-metal bonds and the easy volatility awakened interest on mercury decades ago. The medical use of mercury was virtually complete after the scientific determination of the high toxicity and long biological half life of mercury compounds in vivo. From this follows that the condition precedent to develop new radiopharmaceuticals based on mercury radionuclides is their high specific activity. The production of nca ¹⁹⁷Hg radionuclide together with the short lived ^197mHg isomer is possible by proton or deuteron irradiation of natural gold using a cyclotron. The ¹⁹⁷Au(p,n)¹⁹⁷Hg reaction was applied until now only for small scale tracer production, beam monitoring or stacked foil measurements. The main goal of the research project is the evaluation of the cyclotron-based radionuclides ¹⁹⁷Hg/^197mHg regarding their suitability for diagnostics and therapy of tumors. First results of investigations concerning nca ¹⁹⁷Hg/^197mHg production and the development of bifunctional mercury chelate complexes stable in vivo will be reported.