Program Information
A Method for Performing An In-House Batch Assay of I-125 Seeds Used for Prostate Implants
J Muryn1*, D Wilkinson2 , (1) Cleveland State University, Cleveland, OH, (2) Cleveland Clinic Foundation, Cleveland, OH
Presentations
SU-E-T-41 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The purpose of this work is to evaluate a method for confirming source strength of I-125 seeds in a bulk assay while maintaining sterility and time efficiency.
Methods: The I-125 seeds used in this study (STM 1251, Bard Brachytherapy, Inc.) were available as loose seeds or linked in 3, 4, or 5 seed configurations. A third party 10% assay (NIST traceable) is provided. Source strengths ranging from 0.395 to 0.504 U were available for this study. A stand was built out of aluminum to hold an exposure meter (Inovision (Fluke) 451P) at 25 cm above the I-125 sources to measure the exposure rate. Three different seed configurations were measured: loose, linked, and loaded needles (Bard FastFil Seed Implant Needle). The measurements were made in an operating room, and a sterile sheet was used under the non-sterile aluminum stand. Seeds and needles were placed in a sterile tray.
Results: One hundred forty-two loose seeds in 5 batches (0.395, 0.395, 0.409, 0.444, 0.444 U/seed) and 902 seeds in 7 batches containing various strands (0.444, 0.444, .0444, 0.466, 0.466, 0.504, 0.504 U/seed) were measured. The average exposure rate per unit activity was measured to be 0.593 mR per hr per U with a standard deviation of 0.016. The result for loaded needles was 0.261 mR per hr per U with a standard deviation of 0.014. Once the apparatus is set up, measurements of 180 linked sources as supplied in the Bard package requires only a few minutes.
Conclusion: The proposed method can confirm the activity of a batch of loose or stranded I-125 seeds within a range of 5%.
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