Sensitivity of a helical diode array dosimeter to Volumetric Modulated Arc Therapy delivery errors

Area of Science:

• Medical Physics
• Radiation Oncology

Background:

• Volumetric Modulated Arc Therapy (VMAT) is a complex radiotherapy technique requiring precise delivery.
• Ensuring accuracy in VMAT delivery is crucial for patient safety and treatment efficacy.
• Dosimetric verification tools are essential for quality assurance in VMAT.

Purpose of the Study:

• To evaluate the sensitivity of the ArcCHECK dosimeter in detecting various delivery errors during VMAT.
• To assess the capability of ArcCHECK to identify Multi Leaf Collimator (MLC) position and dose delivery inaccuracies.

Main Methods:

• Simulated gantry-independent, gantry-dependent, and control point-specific MLC and dose errors in prostate and head and neck VMAT plans.
• Utilized ArcCHECK for measurements and analyzed local and global gamma pass rates with 2%/2mm and 3%/3mm tolerances.
• Calculated the clinical impact of the simulated errors.

Main Results:

• ArcCHECK detected minimum 3mm MLC errors and 3% output errors for gantry-independent scenarios with 2%/2mm tolerance.
• Minimum 3mm MLC errors and 3% dose errors were identifiable for gantry-dependent scenarios.
• Errors of 10mm MLC shift and 100% dose error at 4 control points were detected.

Conclusions:

• ArcCHECK, with 2%/2mm criteria and either local or global gamma analysis, reliably detects VMAT delivery errors exceeding specified thresholds.
• The findings support the confident clinical use of ArcCHECK for VMAT quality assurance.
• This study validates ArcCHECK's role in identifying clinically relevant VMAT delivery deviations.