The effect of plan complexity on the uncertainty of gantry angle for VMAT delivery

Volumetric modulated arc therapy (VMAT) is the radiation therapy technique with beam modulation during gantry rotation. The beam is modulated using leaf speed gantry speed instead of dose rate. Gantry angle error is the crucial problem that can influence beam delivery, especially in VMAT plan. Increasing beam modulation represented by plan complexity score may influence treatment error delivery. Hence, the effect of plan complexity on gantry uncertainty needs to be investigated for setting the optimal plan complexity. This study has two purposes: the first was to investigate the correlation between gantry angle error and plan complexity, and the second was to construct the predictive model for predicting gantry angle error.