Room: Stars at Night Ballroom 4
Purpose: To perform the clinical performance of the Halcyon platforms (v1 and v2) for LUNG SBRT and dosimetrically compare then with the Truebeam STx and Truebeam Millenium MLC platforms. The first Halcyon 1.0 platform has been available with fast dual-layer MLC system and MVCBCT for image guidance, while an upgraded version, Halcyon 2.0 has improved MLC design and kVCBCT as additional imaging option.
Methods: 4D CT was performed for all patients in the evaluation study and the AVG reconstruction was used for treatment planning and the 50Gy in 5fxs regiment was applied. 2-arc VMAT plans for Halcyon 1.0 and Halcyon 2.0, as well as, for TB with HDMLC and with Millennium MLC systems were planed based on the institutional optimization objectives for target volumes and OARs and, were evaluated based on their DVH metrics, by the same physician.
Results: All 4 plans met the clinical objectives, overall. The Halcyon 1.0 plan resulted in slightly lower plan quality (i.e. higher OAR doses, reduced conformality) compared to the other plans. Halcyon 2.0 and TB-Millennium MLC resulted in generally comparable plan quality. TB-HDMLC resulted in the highest plan quality. Patient specific QA measurements were performed for both the Halcyon 1.0 and 2.0 plans. Plan specific quality measurements were performed using ArcCheck (by Sun Nuclear) and Portal Dosimetry. Measurements for both plans met clinical acceptability criteria of 90% of points passing 3%, 3mm, global gamma analysis. The Halcyon v1 plan had a higher passing rate for ArcCheck measurements relative to the Halcyon v2 plan.
Conclusion: The Halcyon platform is capable of delivering LUNG SBRT keeping in mind that conformality depends on PTV size with smaller and more irregularly shaped size targets to require higher resolution MLC. Details of the cases studied will be presented.
Funding Support, Disclosures, and Conflict of Interest: supported by Varian Medical Systems