ABSTRACT
High specific activity radioisotopes such as Lu-177, Pm-149, Ho-166 and Rh-105 can be produced by indirect methods involving neutron irradiation of isotopically enriched (e.g. Ru-104) targets producing parent radioisotopes that beta decay to form the desired daughter radioisotopes. For example, Lu-177 can be produced by direct (n, gamma) irradiation of Lu-176. However, only about 20 percent of the Lu-176 atoms are converted to Lu-177 and the long-lived impurity Lu-177m (half-life = 160 days) is also produced in small quantities. Direct irradiation of Yb-176 results in the production of Yb-177 (half-life = 1.9 hr) that beta decays to form Lu-177, with the further advantage that this route of production avoids long-lived Lu-177m. Chemical separation of the Lu-177 from the Yb target results in a high specific activity Lu-177 that can then be used for radiotherapy. Separation of Rh-105 from irradiated Ru-104 targets is also being investigated by volatilization of the Ru