[en] 1. Development of ¹⁶⁵Dy-HMA for the treatment of rheumatoid arthritis 1) Irradiation of 12 mg of ¹⁶⁴Dy₂O₃ in a neutron flux 2x10¹³ n/cm².sec for 4 hours gave ¹⁶⁵Dy₂O₃ showing relatively high specific activity (480 mCi/mg Dy₂O₃) and pure radionuclidic purity (>99.9%). 2) ¹⁶⁵Dy-HMA was prepared from ¹⁶⁵Dy₂O₃ in yield of 80-85% and whose particles size was in 3-8μm range (> 90%) having high stability in vitro. 3) Scintiphoto of rabbit at 24 hours after administration of ¹⁶⁵Dy-HMA into knee joint of a hind leg exhibited the retention of radioactivity with negligible leakage indicating high in vivo stability. 2. Development of ¹⁶⁶Ho-PLAM for the treatment of liver cancer 1) The complex of ¹⁶⁵Ho and acetylacetone was made by reacting aqueous HoCl₃ (pH 5.0) solution with aqueous acetylacetone (pH 9.0) solution, and then recrystalization of the crude product from ethanol gave a pure complex (¹⁶⁵Ho-AcAc) in yield of 58%(mp > 280deg C). 2) Chloroform(1 ml) containing polylactic acid (50 mg) and ¹⁶⁵Ho-AcAc(30 mg) was added to 3% aqueous PVA solution with vigorous stirring, and then microsieving of produced particles gave ¹⁶⁵Ho-PLAM whose size was in 10-45μm range. 3) ¹⁶⁵Ho-PLAM was irradiated by neutron and the subsequent MCA analysis exhibited radionuclidic purity > 99.9% and weight content, respectively. 4) Suspension of ¹⁶⁶Ho-PLAM in human plasma at room temperature for 7 days exhibited very low amount of leaching radioactivity(=0.9%) into plasma indicating in high in vitro stability. 5) Scintiphotos of rabbit taken at 24 hours after i.v administration of ¹⁶⁶Ho-PLAM exhibited excellent retention in lung indicating that the prepared ¹⁶⁶Ho-PLAM has high in vivo stability. (Author)