RADIOASSAYS OF Y-90 USED IN NUCLEAR-MEDICINE

Yttrium-90 radioassays are required in nuclear medicine at the gigabec querel activity level (GBq) for measuring injected activity, and at th e becquerel level for measuring individual tissue samples in biodistri bution studies. A method of standardizing Y-90 for activity using high -efficiency liquid-scintillation counting is described. Solution stand ards were used to establish the calibration factors for commercial rad ionuclide calibrators. Detection efficiencies are also presented for l iquid-scintillation counting, NaI(Tl) bremsstrahlung counting and Cere nkov counting.