Resin 90Y microsphere activity measurements for liver brachytherapy

Area of Science:

• Nuclear Medicine
• Radiotherapy Physics
• Medical Imaging

Background:

• Accurate quantification of radioactive material is essential for effective and safe patient treatment in nuclear medicine procedures.
• Yttrium-90 (90Y) microsphere therapy for liver cancer requires precise measurement of administered radioactivity.
• Variations in measurement geometry and vial types can introduce errors in activity quantification.

Purpose of the Study:

• To establish a reliable method for measuring 90Y microsphere activity for liver brachytherapy.
• To investigate factors affecting activity measurements, including dose calibrator axial response and different vial types.
• To compare the accuracy and reliability of dose calibrator measurements versus radiation survey meters.

Main Methods:

• Activity of 90Y microspheres was measured using a dose calibrator.
• Calibration of the dose calibrator was verified using manufacturer-provided standards.
• Axial response of the dose calibrator was assessed using various vial types (glass shipping, glass V-vial, polycarbonate V-vial).
• Activity measurements were compared between the dose calibrator and a radiation survey meter.

Main Results:

• A reproducible local activity standard was established by verifying the dose calibrator's calibration.
• Dose calibrator measurements showed variations based on vial type: glass shipping vial (0.964), glass V-vial (1.001), and polycarbonate V-vial (0.988).
• Transferring drawn activity to a glass V-vial resulted in a 4% higher dose calibrator reading, while a polycarbonate V-vial showed a 20% increase compared to the shipping vial standard.
• Dose calibrator measurements agreed within 10% with radiation survey meter readings but offered superior geometry and traceability.

Conclusions:

• The dose calibrator method is superior to survey meters for 90Y microsphere activity measurement due to better defined geometry and traceability.
• Local characterization of the activity measurement standard, considering vial-specific effects, is crucial for accurate dosing in 90Y liver brachytherapy.
• Relying solely on manufacturer calibration values without local verification can lead to significant inaccuracies in administered activity.