Determination of the Re-188 Calibration Number for the Capintec CRC- 25PET Dose Calibrator

Background: During the development of novel Re-188 radiopharmaceuticals, it was discovered that no calibration settings were published to calibrate Re-188 on the Capintec CRC-25PET dose calibrator. Methods: Sodium [¹⁸⁸Re]perrhenate was eluted from an OncoBeta ¹⁸⁸W/¹⁸⁸Re generator to measure activity on a Capintec CRC-25R dose calibrator using established dose calibrator settings provided by the manufacturer. The eluent was then used to tune the calibra on settings on a Capintec CRC-25PET dose calibrator, accounting for geometry. Radionuclidic purity of the [¹⁸⁸Re]perrhenate source was verified via gamma spectroscopy. Results: The calibrator number for Re-188 was determined to be 469 x 10 for the Capintec CRC-25PET dose calibrator, which differed from the manufacturer provided calibra on number of 496 x 10 for the Capintec CRC-25R dose calibra on model. W-188 breakthrough was characterised as < 0.01%. Conclusion: This previously unreported calibration number can be used to determine the activity of Re- 188 labelled radiopharmaceuticals using the Capintec CRC-25PET dose calibrator model.