Accuracy evaluation of a Stereotactic Body Radiotherapy system

Geometric accuracy of the frame was verified, including those associated to CT imaging, reconstruction of coordinates by TPSs and positioning of patient (phantom) in treatment couch. Inaccuracies over 5% in absolute dose calculation were detected for points located inside the lung. Smaller deviations are obtained in soft and bone tissue points. The use of rationally designed test cases for dosimetric evaluation of the SBRT systems was established. Problems associated with dose calculation algorithms, especially for considering the lack of lateral electron equilibrium in small fields inside low density regions show the necessity of adequate corrections to ve introduced in order to reduce significant errors in dose estimations. (Author)