Studies on the preparation of labelled compounds for γ-scintigraphy use

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)