Production of 165 Dy for radiation synovectomy, in a low-power (slowpoke) nuclear reactor

Full text: Severe, debilitating pain accompanies inflammation of the synovial membrane in rheumatoid arthritis. Under certain conditions, radiation synovectomy is an effective alternative to surgery for relief of these symptoms. Radionuclides which decay by the emission of beta particles, or beta plus low yields of gamma/x-rays are indicated for this medical application. Of the radionuclides with appropriate decay emissions, half-life and physical/chemical properties, 165Dy is a suitable candidate for production in a low-power reactor. Literature methods for production of this radiopharmaceutical usually involve irradiating solid Dy(OH)3 , which is dissolved in HCl to form DyCl3 and then re-precipitated under controlled conditions using NaOH, to produce the desired particle size for medical use. A procedure in which most or all of this post-irradiation processing can be eliminated is particularly important when using low neutron flux reactors, in order to avoid reductions in the amount of deliverable radiopharmaceutical. Radiological safety considerations may also necessitate avoiding post-irradiation processing, since low-power reactor facilities usually have no appropriate hot cells for extensive manipulation of highly active samples. Appropriately-sized, pre-formed Dy(OH)3 particles were produced under a variety of conditions in attempts to produce a stable, sodium-free product that would be suitable for irradiation and use without further processing. Sodium content could be reduced to about <5 ppm by washing with pure water, but further washes seriously eroded the Dy particles, so that the majority of the particles remaining were <1 μ, too small for use in radiation synovectomy. Exploratory irradiation's were performed to confirm that usable specific activities were attainable in sufficient yield for medical use. Data on 165Dy production yields and particle characteristics will be presented in support of this concept