A novel constancy check technique for a well type ionisation chamber using a ⁹⁰Sr plane-parallel check source

Area of Science:

• Medical Physics
• Radiotherapy Dosimetry
• Radiation Oncology

Background:

• Accurate source strength determination is crucial for safe and effective brachytherapy.
• Well-type ionization chambers are recommended detectors for source strength measurements.
• Maintaining stable detector response and valid calibration is essential for radiotherapy treatments.

Purpose of the Study:

• To develop and validate a novel technique for constancy checks of well ionization chambers.
• To assess the feasibility of using a Sr-90 check source for routine well chamber calibration verification.
• To establish a cost-effective and robust method for ensuring the accuracy of brachytherapy source strength measurements.

Main Methods:

• A new Standard Imaging Inc. HDR-1000 Plus well chamber was commissioned for clinical use.
• A novel technique was developed utilizing a Sr-90 check source (PTW model T48010) for well chamber constancy checks.
• The methodology was designed to be simple, robust, and accurate for measuring well chamber constancy.

Main Results:

• The developed methodology demonstrated sufficient accuracy to measure well chamber constancy within ±0.5%.
• The technique leverages existing Sr-90 check sources commonly available in radiotherapy departments.
• No additional equipment purchase is required, making the method highly cost-effective.

Conclusions:

• The proposed Sr-90 check source methodology provides a simple, robust, and cost-effective means for performing constancy checks on well ionization chambers.
• This technique ensures the continued accuracy of source strength determination in brachytherapy, contributing to safe and effective patient treatments.
• Radiotherapy departments can readily implement this method using readily available equipment, enhancing quality assurance in brachytherapy dosimetry.