Optimal threshold of a control parameter for tomotherapy respiratory tracking: A phantom study.

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Radixact Synchrony® is a real-time motion tracking system for helical tomotherapy.
• It uses potential difference to predict target motion accuracy, measured as 3D distance error.
• Optimal potential difference thresholds for Radixact Synchrony® require further investigation.

Purpose of the Study:

• To determine the optimal potential difference threshold for Radixact Synchrony® during respiratory tumor-motion-tracking irradiation.

Main Methods:

• Evaluated dosimetric and motion tracking accuracy using a moving phantom with various respiratory models.
• Assessed gamma analysis (3%, 1 mm, 10% dose threshold) for dosimetric accuracy.
• Determined the optimal potential difference threshold using receiver operating characteristic (ROC) analysis.

Main Results:

• A strong linear correlation was found between potential difference and gamma-pass ratio (R = -0.704).
• Potential difference also correlated linearly with distance error (R = 0.827), though it tended to underestimate error at higher values.
• ROC analysis identified an optimal potential difference cutoff of 3.05 mm.

Conclusions:

• Potential difference effectively predicts irradiation accuracy during Radixact Synchrony® motion tracking.
• A potential difference threshold of approximately 3 mm is recommended for optimal accuracy.