Regression Equation for Predicting Source Strength Detection Rate in Iodine-125 Seed Brachytherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Medicine

Background:

• Prostate cancer incidence is rising globally, increasing demand for treatments like iodine-125 (125I) seed brachytherapy.
• Inaccurate source activity in 125I seeds can compromise treatment efficacy and patient safety.
• Low verification rates of seed activity and number in Japan necessitate improved quality assurance protocols.

Purpose of the Study:

• To validate a regression equation for predicting accurate source strength detection rates based on the number of radiation sources.
• To provide a reliable method for facilities to verify 125I seed activity, addressing challenges with single-seed assays in Japan.

Main Methods:

• Utilized a batch assay method with a well-type ionization chamber (CRC-15R) to measure source intensity detection rates.
• Collected data on AgX100 seeds and employed Microsoft Excel 2019 to calculate a regression equation correlating source number to detection rate.
• Established specific control limits (acceptance and intervention) for batch assay results.

Main Results:

• Developed and validated a regression equation to predict appropriate detection rates for varying numbers of 125I radiation sources.
• The study provides a practical alternative to single-seed assays for source strength verification in 125I brachytherapy.

Conclusions:

• The validated regression equation offers a crucial reference for facilities performing or planning 125I seed brachytherapy.
• Accurate source strength measurement is critical for ensuring the safety and effectiveness of prostate cancer brachytherapy.