Validation of the Calypso Surface Beacon Transponder

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• The Calypso L-shaped Surface Beacon transponder is a novel device for clinical applications.
• Accurate real-time tracking of patient motion is crucial in radiotherapy.

Purpose of the Study:

• To validate the Calypso Surface Beacon transponder's performance.
• To assess its stability, reproducibility, orientation sensitivity, cycle rate dependence, and respiratory waveform tracking accuracy.

Main Methods:

• Utilized a Quasar respiratory phantom to simulate breathing waveforms.
• Tracked transponder motion under various conditions including different cycle rates and orientations.
• Analyzed data for amplitude, standard deviation (SD), drift, and positional accuracy.

Main Results:

• Demonstrated high stability with minimal drift (e.g., 5.1 × 10-5 mm/s at 0% phase).
• Achieved excellent reproducibility with combined SDs of 0.07 mm (0% phase) and 0.11 mm (50% phase).
• Showed submillimeter resolution (SD of 0.233 mm) in respiratory waveform tracking accuracy over extended periods.

Conclusions:

• The Calypso Surface Beacon transponder is stable, accurate, and reproducible for clinical use.
• It reliably achieves submillimeter resolution for tracking both breathing and simulated sinusoidal waveforms.
• This validation supports its utility in real-time patient motion monitoring during treatments.