THE TCAP PROJECT
Production of highly enriched 99Mo/99mTc at cyclotrons based on natural molybdenum.
The TCAP project aims at the production with cyclotrons of Tc99m for medical use from natural Mo98. The DPNC Geneva and the group of Prof. Roger Alberto of the Chemistry Departments of the University of Zurich participate to the research project, with scientific contacts with CERN and PSI. A preliminary test on the chemical separation of a Mo compound irradiated at the Ljubljana reactor gave encouraging results. The TCAP project is presently going on thanks to a grant by the Boninchi Foundation.
In diagnostic medicine, the application of radionuclides plays a major role for identifying lesions in e.g. cancer, or to monitor the progress or regress of a disease after treatment. Nuclear medicine relies for these purposes on a relatively limited number of radionuclides. Among them, technetium-99m (99mTc) still accounts for more than 80% of all imaging procedures worldwide. There are essentially two different modalities for nuclear medicinal imaging, Positron Emitting Tomography (PET) with radionuclides such as 18F and recently 68Ga, and Single Photon Emission Computed Tomography (SPECT) with radionuclides such as 99mTc, 111In and a few other radionuclides. 99mTc is by far the most important radionuclides since it emits photons at a very good energy, not burdening patients with large doses, has a clinically useful half-life time of 6h and, probably most importantly, is cheap in comparison to all other radionuclides. In clinics, 99mTc is available from a molybdenum-99/technetium-99m generator (99Mo/99mTc). In this device, [99MoO4]2- with a half-life time of 67h is loaded on a column and decays to [99mTcO4]- which can be eluted by a nurse every day. It is thus “online”, available without the need for a cyclotron. The nurse then converts the solution to the radiopharmaceutical of interest with commercially available kits.
The molybdenum required for these generators (99Mo) is prepared from highly enriched uranium. This uranium undergoes fission in a few old-generation reactors worldwide. From the fission products, 99Mo is separated as [99MoO4]2-. It is thus present with the highest possible specific activity, i.e. only 99Mo is present while essentially no other molybdenum isotopes are. This procedure makes the supply of 99Mo for nuclear medicine generators dependent on a few reactors that will be shut down in the next years for maintenance or permanently. This jeopardizes the production of urgently needed 99Mo/99mTc generators in clinics. Therefore, finding alternative production methods is necessary.
This project aims at a cheap and scientifically innovative method for the preparation of this radionuclide with high specific activity based on natural molybdenum.