Technical Note: Scintillation markers for real-time visual source tracking during skin high dose rate brachytherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Materials Science

Background:

• High dose rate (HDR) brachytherapy treatments are susceptible to errors from manual data entry and hardware connections, particularly with complex surface applicators.
• These errors can lead to treatment misadministration and compromise patient safety.
• Quality assurance (QA) in HDR brachytherapy requires robust methods to prevent such errors.

Purpose of the Study:

• To develop and evaluate a simple, real-time visual verification method for HDR surface brachytherapy.
• To reduce manual errors in catheter length entry and hardware connections.
• To enhance patient safety by improving QA measures.

Main Methods:

• Fabricated cerium-doped lutetium yttrium orthosilicate (LYSO) scintillation markers (5-mm diameter) embedded in a polymer.
• Attached markers to a Freiburg flap applicator to verify catheter-transfer tube connections using an ¹⁹² Ir source.
• Placed markers along the target periphery to confirm source reach and visually tracked the HDR source via marker illumination, even through thermoplastic material.

Main Results:

• Scintillation markers emitted intense blue light when irradiated by the HDR source, confirming its presence in the correct catheter.
• The visual signal was discernible even with thermoplastic material overlaying the applicator.
• Light intensity crosstalk between adjacent catheters was less than 50% of the maximum.

Conclusions:

• Developed scintillation markers and paint enable successful visual tracking of the HDR source in surface brachytherapy.
• Direct source visualization allows real-time catheter verification and confirmation of superficial target coverage, preventing medical events.
• This method can be readily integrated into existing QA programs.