⁹⁰Y SIR-Spheres Activity Measurement with New SIROS D-Vial Delivery Kit

A new ⁹⁰Y SIR-Spheres delivery kit (SIROS D-vial and shield) has been introduced with a different physical form from the legacy V-Vial kit. Here, we establish the dose calibrator settings and exposure-rate-to-activity conversion factor to assay ⁹⁰Y SIR-Spheres activity in the new SIROS kit. Methods: Eight D-vials with initial ⁹⁰Y activities from 1.2 to 6.6 GBq within acrylic shields were assayed with dose calibrators and exposure-rate meters until activities decayed to approximately 0.1 GBq. The dose calibrator settings resulting in the lowest median activity errors and the best-fit slope of exposure rate versus activity were identified. Results: SIROS D-vial ⁹⁰Y activity can be accurately and reliably estimated directly using setting 51 × 10 on both the CRC-15R and the CRC-55tR dose calibrators (errors within ±0.5%) and indirectly with an exposure-rate reading at 30 cm using conversion factor 0.664 ± 0.003 GBq/(mR/h) (R ² = 0.985). Conclusion: Dose calibrator settings and exposure-rate-to-activity conversion factor for ⁹⁰Y activity assays with new SIROS kit should be updated from legacy V-Vial parameters to avoid an approximately 10% underestimation.