A Beam Orientation Quality Assurance Framework for Gyroscopic Stereotactic Radiosurgery Systems

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Gyroscopic stereotactic radiosurgery (SRS) systems offer precise radiation delivery.
• Standard quality assurance (QA) protocols may not assess beam entry angle consistency, crucial for peripheral dose.
• Angular variations can impact critical structure dosimetry despite target accuracy.

Purpose of the Study:

• To develop and validate a practical QA framework for monitoring beam orientation in gyroscopic SRS.
• To assess the sensitivity and reproducibility of the proposed QA method.
• To enhance treatment fidelity and patient safety in SRS.

Main Methods:

• Utilized the ArcCHECK cylindrical diode array (1,386 diodes) for beam orientation monitoring.
• Developed a calibration protocol using a 44-beam QA plan with varying collimator sizes.
• Quantified sensitivity to beam rotation as diode failures per degree of angular deviation.

Main Results:

• The 10 mm collimator showed optimal sensitivity (37.7% per degree) due to penumbra-diode spacing match.
• Daily QA measurements demonstrated high reproducibility and sensitivity.
• A 0.8° angular error was accurately detected and quantified.

Conclusions:

• The developed QA framework provides a reliable and efficient method for tracking beam orientation consistency in gyroscopic SRS.
• This approach requires no additional hardware or major workflow changes.
• Integration of angular QA improves treatment fidelity and patient safety in gyroscopic SRS.