Secondary standards for ²²³Ra revised.

Area of Science:

• Nuclear Medicine
• Metrology
• Radiopharmaceutical Calibration

Background:

• Previous NIST-published dose calibrator settings from 2010 were found to be inaccurate.
• A critical error in the calibration chain led to underestimated radiopharmaceutical activity readings by approximately 10%.

Purpose of the Study:

• To report new, accurate calibration factors for dose calibrators.
• To re-evaluate previous calibration data in light of a newly discovered error.
• To provide revised calibration factors for various clinical geometries.

Main Methods:

• Directly linking new calibration factors to updated NIST primary standards.
• Revisiting and re-analyzing raw data from the original 2010 calibration experiments.
• Comparing new experimental results with revised calibration factors.

Main Results:

• New calibration factors, directly traceable to current NIST standards, have been determined.
• Re-evaluation confirmed the necessity for correction, validating the new factors.
• Revised calibration factors for multiple clinical geometries are presented.

Conclusions:

• The previously reported 2010 dose calibrator settings are confirmed to be erroneous, causing a ~10% underestimation of activity.
• Updated calibration factors are provided, ensuring more accurate radiopharmaceutical measurements.
• The fundamental conclusions regarding geometry effects from the 2010 study remain valid.