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Session Chairperson: Dr. Urs O. Hafeli, Project Scientist, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195
DEVELOPMENT OF A METALLIC RADIOACTIVE RHENIUM SOURCE FOR THE TREATMENT OF RESTENOSIS AFTER ANGIOPLASTY: Urs Hafeli, Eric Lee, Jay Ciezki, Roger Macklis, The Cleveland Clinic Foundation, Desk T28, 9500 Euclid Ave., Cleveland, OH 44195
Radioactive Rhenium sources can be prepared in a nuclear reactor by bombarding the non-radioactive metal with neutrons. In a -reaction, the two -emitters 186Re and 188Re are produced with high yield. One application of thus prepared radioactive Rhenium wires is the prevention and treatment of restenosis after balloon angioplasty. For this brachytherapeutic application, the source must be very stable, enclosed and safe to handle. The necessary encapsulation of the radioactive source was done by plasma coating with a 240 nm layer of titanium, as confirmed by scanning electron microscopy. This resulted in a highly radiochemically stable source. The response of endothelium and smooth muscle cells to a radioactive Rhenium-wire and its dosimetry was determined in an in vitro cell model. Our results confirmed that radioactive sources made from 186Re and, even more so, 188Re, are excellent candidates for restenosis inhibition because of their narrow treatment range, sharp dose gradient, inexpensive preparation, excellent stability, easy shielding and conveniently short treatment times.
PRODUCTION OF RHENIUM-186 AND RHENIUM-188 AT ORNL HFIR: Saed Mirzadeh, A.L. Beets, F.F. (Russ) Knapp, Nuclear Medicine Group, Health Science Research Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN 37831-6229
PRODUCTION OF RHENIUM-POWDER WITH A JET MILL AND ITS INCORPORATION IN RADIOACTIVE MICROSPHERES FOR THE TREATMENT OF LIVER TUMORS: Urs Hafeli, Gayle Pauer, Roger Macklis, The Cleveland Clinic Foundation, Desk T28, 9500 Euclid Ave., Cleveland, OH 44195; Randall German, Penn State University, 118 Research Building West, University Park, PA 16802-6809
Metallic rhenium powder of 325 mesh is readily available. Well characterized powder of micrometer size, however, is less easy to obtain. In this presentation, we describe how we prepared rhenium powder with an average particle size of 1-2 µm, starting from 325 mesh material and using a jet mill. The particle size distribution was confirmed by light and scanning electron microscopy, and laser diffraction. The change in density and surface characteristics (porosity) was also analyzed. Biodegradable poly(lactic acid) microspheres were prepared, by a solvent evaporation method, from the resulting rhenium particles and were neutron activated in a nuclear reactor to directly yield 186/188Re-microspheres, useful for the treatment of liver tumors. Biodistribution data in rats as well as first treatment results of Novikoff tumors are presented.
RADIOIMMUNOTHERAPY WITH RHENIUM-186 AND RHENIUM-188: Alan R. Fritzberg, Fu-Min Su, NeoRx Corporation, 410 W. Harrison, Seattle, WA 98119
The radioisotopes of rhenium, Re-186 and Re-188, have physical properties that make them attractive for radiotherapy via antibody mediated targeting. Rhenium186 has a half life of 3.78 days, maximum beta energy of 1.07 MeV and imageable gamma rays. Rhenium-188 has a half life of 17 hours, maximum beta energy of 2.12 MeV and imageable gamma rays. Rhenium-186~with its longer half life is appropriately matched with the larger antibody forms, IgG of 150 kD molecular weight and its F(ab')2 fragment of 100 kD size. Rhenium-188 with its shorter half life may be preferred in instances of rapid tumor uptake and shorter tumor retention. N,S amide thiolate chelating agents such as mercaptoacetylglycylglycyl--aminobutyrate have been developed for the attachment of the rhenium radioisotopes to antibodies. With this agent, over 150 patients with solid tumors have been treated with up to 550 mCi of Re-186. Several have had partial responses (> 50% decrease in tumor size).
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