To Advance Cancer Therapy, University Starts Producing Terbium-161

The Science

Newswise — Theranostic agents are substances that can both diagnose and treat cancer at the same time. One such substance is the radioactive isotope terbium-161 (Tb-161). Researchers have shown that Tb-161 can be produced at high purity using a low-power university research reactor. The project produced Tb-161 by irradiating gadolinium-160 (Gd-160) targets. It demonstrated that these two isotopes can be efficiently separated. The resulting Tb-161 had the purity needed for use in medical applications.

The Impact

Tb-161 is a powerful theranostic agent because of the way it breaks down, or decays. As it decays, Tb-161 releases three types of particles: beta particles (high-energy electrons), low-energy electrons, and low-energy photons. The beta particles are useful for treating larger tumors, while the low-energy electrons are effective at treating very small tumors or potentially, single cancer cells. The low-energy photons allow doctors to image where the radioactive isotope is in the body. These functions enable doctors to use the isotope to diagnose and treat cancer at the same time.

Summary

Tb-161 is a medical radioisotope with a half-life of approximately 7 days, meaning that it loses half of its radioactivity in a week. In this study, researchers from the University of Utah, in collaboration with the University of Missouri, produced Tb-161 using the University of Utah’s TRIGA research reactors. These low-power reactors are used for training and research. In the reactors, Gd-160 target materials are exposed to neutrons. This causes the Gd-160 to absorb a neutron and transform into Gd-161, which then quickly decays into Tb-161. This process is advantageous because it produces a new element (Tb-161) that can be separated from the original material (Gd-160). This is unlike traditional methods where the product is chemically identical to the target.

Separating two neighboring elements can be difficult, but this study developed a three-step process to efficiently isolate Tb-161 from gadolinium. First, the researchers removed most of the original gadolinium, which makes up the bulk of the target. Next, they concentrated the remaining material and repeated the process to improve efficiency. Finally, they performed a final cleanup step to remove any residual gadolinium, yielding research-scale quantities (2 to 8 millicuries) of high-purity Tb-161. To confirm the product’s suitability for further research, the scientists tested its purity and found it met the standards required for medical applications. This approach shows that low-power research reactors can be valuable tools for producing important medical radioisotopes.

Funding

This research is supported by the Department of Energy (DOE) Isotope Program, managed by the DOE Office of Science for Isotope R&D and Production. This work was also supported in part by the United States Nuclear Regulatory Commission Fellowship.