Feasibility study for production and quality control of Yb-175 as a byproduct of no carrier added Lu-177 preparation for radiolabeling of DOTMP.

Skeletal uptake of β- emitters of DOTMP complexes is used for the bone pain palliation. In this study, two moderate energy β- emitters, 177 Lu (T1/2  = 6.7 days, Eβmax  = 497 keV) and 175 Yb (T1/2  = 4.2 days, Eβmax  = 480 keV), are considered as potential agents for the development of the bone-seeking radiopharmaceuticals. Since the specific activity of the radiolabelled carrier molecules should be high, the non-carrier-added (NCA) radionuclides have an effective role in nuclear medicine. Many researchers have presented the synthesis of NCA 177 Lu. Among these separation techniques, extraction chromatography has been considered more capable than other methods. In this study, a new approach, in addition to production of NCA 177 Lu by EXC procedure is using pure 175 Yb that was usually considered as a waste material in this method but because of high radionuclidic purity of 175 Yb produced by this method we used it for radiolabeling as well as NCA 177 Lu. To obtain optimum conditions, some effective factors on separation of Lu/Yb by EXC were investigated. The NCA 177 Lu and pure 175 Yb were produced with radionuclidic purity of 99.99 and 99.97% respectively by irradiation of enriched 176 Yb target in thermal neutron flux of 5 × 1013  n/cm2 s for 14 days. 177 Lu-DOTMP and 175 Yb-DOTMP were obtained with high radiochemical purities (> 95%) under optimized reaction conditions. Two radiolabeled complexes exhibited excellent stability at room temperature. Biodistribution studies in rats showed favorable selective skeletal uptake with rapid clearance from blood along with insignificant accumulation of activity in other non-target organs for two radiolabelled complexes.