[DY-166]DYSPROSIUM [HO-166]HOLMIUM IN-VIVO GENERATOR/

A novel approach for the delivery of Ho-166 (t1/2 = 26.6 h) to tissue is via the in vivo decay of its 81.5 h parent, Dy-166-an in vivo gener ator system. A critical question for the in vivo Dy-166/Ho-166 generat or system is whether translocation of the daughter nucleus occurs. The in vitro and in vivo integrity of the [Dy-166]Dy/Ho-166-DTPA complex was investigated and results indicated that no translocation of the da ughter nucleus occurs subsequent to beta(-) decay of Dy-166. Biodistri bution studies of [Dy-166]Dy-DTPA showed that the ratio of Dy-166/Ho-1 66 in bone remains constant (+/-7%) over a 20 h period, indicating no significant in vivo loss of Ho-166 from the complex. Increasing the in vivo residence time of [Dy-166]Dy-DTPA complex attached to HSA gave s imilar results.