HDR brachytherapy afterloader quality assurance optimization using monolithic silicon strip detectors.

Area of Science:

• Medical Physics
• Radiation Oncology
• Brachytherapy Technology

Background:

• Current quality assurance (QA) methods for high dose-rate (HDR) brachytherapy afterloaders lack comprehensive tools for simultaneous assessment of positional, temporal, transit velocity, and air kerma strength (AKS) accuracy.
• Existing QA protocols often rely on less precise methods like closed-circuit television and stopwatches.

Purpose of the Study:

• To develop a precise and rigorous technique for daily QA of HDR brachytherapy afterloaders.
• To incorporate the assessment of dwell position accuracy, dwell time accuracy, transit velocity consistency, and relative air kerma strength (AKS) of an Ir-192 source.

Main Methods:

• A Sharp ProGuide catheter was positioned above a 256-channel diode array (DMG256) detector.
• The Flexitron HDR afterloader delivered radioactive sources to specific dwell positions and times.
• Data acquisition system (DAQ) and Python scripting were used for live readout, post-processing, and analysis of positional and temporal localization.

Main Results:

• The DMG256 achieved relative air kerma strength (AKS) measurements within 0.6%-3.0% of expected activity over 7 weeks.
• Transit velocity was measured with an average of (10.88 ± 1.01) cm/s for 13 mm steps, demonstrating sub-millisecond temporal accuracy.
• Dwell position localization accuracy was between 0.1 and 0.3 mm (3σ) for various step sizes, with a fixed temporal accuracy of 10 ms.

Conclusions:

• The DMG256 silicon strip detector provides a more precise method for daily QA of HDR afterloader dwell position and dwell time accuracy compared to current standards.
• This advanced QA tool enables measurements of transit velocity/time and relative AKS, which are not feasible with conventional techniques.
• The DMG256 enhances the rigor and precision of brachytherapy afterloader quality assurance.