Purpose: To verify the feasibility of a non-metallic in-house-developed mini 6DoF plate for an end-to-end test of surface-guided radiotherapy (SGRT).
Methods: The STEEV phantom (CIRS) was CT scanned and a dynamic conformal arc plan was generated. The target was planned at the location of an ion chamber insert. The dynamic arc plan went from 270 to 90 degrees. The STEEV phantom was placed onto the 6 DoF plate and aligned to surface markers based on in-room lasers. The phantom and mini-couch were moved to isocenter alignment using the IGRT table. A surface reference capture was acquired and a full arc delivery was measured using an ion chamber (FC65-G). Additional fields were generated with the original plan, with the arcs split into 6 30-degree arcs. Each 30-degree arc was delivered and measured with the ion chamber. Between each arc delivery, the SRS phantom was moved randomly by adjusting the level of the mini-couch manually. The deviating motion was tracked using Identify, an SGRT system powered by Varian, and adjusted back to the surface reference position using the IGRT couch. The charge recorded was compared between the original full arc and the cumulative charge from 30-degree arcs after correcting for the phantom position. The delivery was repeated twice, including one comparison with EBT3 GafChromic film inserted.
Results: The phantom was able to be corrected to within 0.1 cm (translations) and 0.2 degrees (rotations) of the surface reference capture before all arcs. The measured charge agreement between the two deliveries was 99.55%. Film measurements agreed well, with 97.2% gamma pass under 2%/2mm criteria.
Conclusion: The proposed mini plate shows the potential for providing a rigorous QA of SGRT. It can also be used for real-time automated positional corrections in 6D.
Stereotactic Radiosurgery, Immobilization, Patient Positioning
TH- RT Interfraction Motion Management: Development (new technology and techniques)