A new Os-191->Ir-191m generator for radionuclide angiocardiography

Ultrashort-lived radionuclides offer several advantages in angiocardiography in comparison to Tc-99m. Of the isotopes proposed for this application, Ir-191m (T/sub 1/2/=5 s) has several advantages when compared to Au-195m (T /sub 1/2/=30.5 s) (longer generator shelf-life) and Ag-109m (T/sub 1/2/=40 s) (higher photon yield). The Ir-191m generator currently in clinical use suffers, however, from low Ir-191m yield (10% ml) and relatively high breakthrough of the Os-191 parent (5x10/sup -3/%/ml). The authors recently developed a new Ir-191m generator that offers higher yield (20-30%/ml) and lower breakthrough (5x10/sup -4/%/ml) using an eluent that is only slightly hypertonic and does not require buffering prior to injection. A biodistribution study in mice shows the Os-191 breakthrough products, which are responsible for 80% of the patient radiation dose, to be cleared from the body more quickly than those of the earlier generator. This combination of 2-3 times higher yield, ten times lower breakthrough, and more rapid excretion results in a 30-50 fold decrease in the patient absorbed dose per study when compared to the earlier design. An additional advantage is the absence of a ''scavenger'' column. More than 200 radionuclide agiograms have been recorded in dogs with no adverse reactions and preliminary studies in mice have revealed no toxic effects attributable to the eluate