Performance evaluation of the CyberKnife system in real-time target tracking during beam delivery using a moving...

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Accurate tumor targeting is crucial in radiation therapy.
• Respiratory motion can significantly impact treatment precision.
• The Synchrony Respiratory Tracking system aims to mitigate these motion-related errors.

Purpose of the Study:

• To evaluate the tracking error of the Synchrony Respiratory Tracking system.
• To determine the variation in tracking beams during simulated respiratory motion.

Main Methods:

• A moving phantom with fiducial markers simulated respiratory motion (SI and AP directions).
• A 2D detector array recorded beam data during stationary and sinusoidal motion (6-s cycle, 15/20-mm amplitude).
• Beam center shifts were calculated from movie files with 100-ms sampling.

Main Results:

• The mean targeting error (Ep95) was 0.28 ± 0.08 mm under stationary conditions.
• Under sinusoidal respiratory motion, the mean Ep95 was 0.66 ± 0.23 mm (range: 0.28–1.22 mm).
• The maximum beam center drift observed was 2.7 mm, with a maximum tracking error < 1.5 mm for motion amplitudes up to 20 mm.

Conclusions:

• The CyberKnife Synchrony system's tracking accuracy was validated using a moving phantom and 2D detector array.
• The system demonstrates effective tracking of respiratory motion within specified parameters.
• Results indicate the system's potential for improving treatment accuracy in the presence of respiratory motion.