TDCR Cherenkov counting for determining ⁹⁰Y activity in blood samples

Yttrium-90 (⁹⁰Y) microsphere radioembolization is a promising internal therapy for treatment of hepatic tumors. Development of a precise method for measuring the activity of ⁹⁰Y in blood samples is needed to facilitate preclinical safety assessment of drugs. This paper presents the development of a triple-to-double coincidence ratio (TDCR) Cherenkov counting method for quantifying blood ⁹⁰Y activity. The impact of heating temperature and the quantities of nitric acid and H₂O₂ on wet oxidation of blood were studied for rapid sample preparation. Elevated heating temperatures and the addition of concentrated nitric acid expedited blood decolorization and effectively suppressed chemiluminescence interference. The addition of H₂O₂ also accelerated blood decomposition while mitigating sample color quenching. The digested samples were counted using a Hidex 300SL liquid scintillation counter for 5 minutes, and a minimum detectable activity of 0.31 kBq/L was achieved with the region of interest (ROI) analysis window set at 80–300 channels. The method was validated using whole blood samples spiked with varying activities of ⁹⁰Y in the range of 3.37–51.15 kBq/L.