A Technique for Measurement of Strontium-89 in a Dose Calibrator

Abstract

Objective: Strontium-89 (Metastron®, Medi-Physics Inc., Arlington Heights, IL) has recently received U.S. Food and Drug Administration approval as a therapeutic agent for relief of bone pain in patients with painful skeletal metastases. However, there are no calibration settings specified for measurement of ⁸⁹Sr in a dose calibrator.

Methods: Our institution developed a technique to determine the correct dose calibrator setting for measurement of ⁸⁹Sr both in the vial, as received from the manufacturer, and in the syringe for patient administration. The labeled activity in the ⁸⁹Sr vial was initially decay-corrected to the current date and time. The vial was then placed in a dose calibrator (CRC®-12, Capintec, Inc., Ramsey, NJ), and the potentiometer was adjusted until the displayed activity and the calculated activity were the same (after the displayed reading was multiplied by a conversion factor of 100). This technique was then repeated using another Capintec dose calibrator. The same procedure was applied to the ⁸⁹Sr measurement in the syringe. The amount of ⁸⁹Sr activity withdrawn into the 6-ml syringe was determined by subtracting the residual activity contained in the vial (using the same dial setting for the vial) from the original vial activity.

Results: The calibration settings obtained for ⁸⁹Sr measurement in a vial or syringe were very similar on both dose calibrators.

Conclusion: This technique may be useful to others who wish to determine dose calibrator settings for measurement of ⁸⁹Sr.