Development of secondary standards for 223Ra

Ra-223 is a bone-seeking alpha emitter currently being evaluated as a radiopharmaceutical. Concurrent with the primary standardization, NIST established that calibration factors currently used for radionuclide calibrators in the clinical setting give readings 5.7–8.7% higher than the NIST calibrated activity. This work describes the determination of calibration factors specific to dose vials and syringes. Using the calibration factors derived with standard ampoules to measure syringe activities can give readings up to 3.6% too high.