Room: Exhibit Hall | Forum 3
Purpose: To develop a new machine dedicated to whole-body stereotactic radiotherapy (SRT) treatment.
Methods: This SRT-dedicated treatment device (CybeRayTM) utilizes multiple radiation sources and focusing beams to achieve high dose in the target and sharp dose gradient to spare the normal tissue. It has following key modules: (1) a ring-type gantry providing high isocenter accuracy and allowing non-coplanar and multi-arc beam delivery; (2) a treatment head with 13 Cobalt sources and a focusing beam collimation system; (3) an integrated kV-imaging system providing cone-beam CT based positioning and rotational kV-imaging based intra-fractional motion monitoring; (4) an integrated electronic portal imaging device (EPID) allowing automatic beam quality assurance (QA).; and (5) a specially designed treatment planning system. Extensive tests were conducted according to the international standards for radiotherapy device. In addition to the safety tests, performance tests covered the mechanical accuracy, end-to-end positioning accuracy, end-to-end dosimetry accuracy, dosimetry properties, real-time imaging accuracy, beam verification and treatment plan quality evaluated by comparison with other well established treatment techniques for clinical cases.
Results: CybeRayTM provides superior dosimetry properties with beam penumbra of 3.5mm, and 6~10 time less dose at the out-layer region for a full arc delivery comparing to 6MV beam. Superior dose distributions for patient treatment with less normal tissue dose are also achieved comparing to IMRT and Cyberknife, especially for lung cancer treatment. The treatment isocenter accuracy is 0.3mm. End-to-end treatment positioning error with image guidance is less than 0.6mm, and end-to-end dosimetry error is less than 0.5%. For real-time image guidance, the response time is 1.5s and the positioning accuracy is 0.7 mm. A 0.5mm collimator offset can be identified by the EPID QA module.
Conclusion: A new whole-body stereotactic RT device has been developed and tested. It is able to provide superior dose distribution for small target SRT treatment.