Accuracy analysis of the dose delivery process while using the Xsight® Spine Tracking technology

The Accuray CyberKnife (R) system provides radiotherapy for the treatment of moving lung tumors, thanks to the use of the Xsight (R) Lung Tracking technology for monitoring the motion of the target. However, there are situations in which this technology is not able to properly track the target. Thus, the aim of the proposed work is to study the accuracy of the dose delivery process while using the Xsight (R) Spine Tracking technology, which helps to overcome the aforementioned issue. The CIRS Dynamic Thorax Phantom was used to simulate the motion of a spherical target (diameter 2 cm), which moves along the craniocaudal direction (motion 3 cm). Monte Carlo algorithm calculated PTV and ITV treatment plans for isocentric and non-isocentric irradiation methods. Ionization Chamber and Film Dosimetry measurements were performed to study the accuracy of the dose delivery process to the center, and to the periphery of the tumor. Results obtained through the implementation of the PTV treatment plans were used as a baseline to analyze the accuracy of dose delivery for ITV plans. Although results indicated a decrease for the dose delivered compared to the planned one, the dose delivered was not lower than the prescribed one in any of the studied cases.