Purpose
To evaluate a plastic scintillator detector for patient‐specific quality assurance of VMAT radiosurgery plans.
Methods
The detector was comprised of a 1 mm diameter, 1 mm high plastic scintillator coupled to an acrylic optical fiber. Sixty VMAT SRS plans for treatment of single targets having sizes ranging from 3 mm to 30.2 mm equivalent diameter (median 16.3 mm) were selected. The plans were delivered to a 20 cm × 20 cm x 15 cm water equivalent plastic phantom having either the plastic scintillator detector or radiochromic film at the center. Calibration films were obtained for each measurement session. The films were scanned and converted to dose using a 3‐channel technique.
Results
The mean difference between plastic scintillator and film was ‒0.45% (95% confidence interval ‒0.1% to 0.8%). For target equivalent diameter smaller than the median, the mean difference was 1.1% (95% confidence interval 0.5% to 1.7%). For targets larger than the median, the mean difference was ‒0.2% (95% confidence interval ‒0.7% to 0.1%).
Conclusions
The plastic scintillator detector response is independent of target size for targets as small as 3 mm and is well‐suited for patient‐specific quality assurance of VMAT SRS plans. Further work is needed to evaluate the accuracy for VMAT plans that treat multiple targets using a single isocenter.