(Wednesday, 7/17/2019) 10:00 AM - 10:30 AM
Room: Exhibit Hall | Forum 7
Purpose: This study evaluates the feasibility of HyperArc technology (Varian Medical Systems) for hippocampal avoidance whole-brain radiotherapy (HA-WBRT).
Methods: Five patients previously treated with HA-WBRT were re-planned using HyperArc modality. HyperArc is a non-coplanar volumetric modulated arc therapy technique based on 4 fixed arcs with automatic isocenter placement and optimized collimator rotation per arc field.HyperArc plans were generated for a dose of 30Gy in 10 fractions for 6 MV filter free photon energy.Planning target volumes (PTV) and organs at risk (OAR) outlined following NRG-CC001 guidelines were used for plan optimization. No pseudo-structures were created by the planner. A set of reproducible constraints identified for all patients was used for optimization. Plans were delivered using the automated treatment delivery and treatment times were recorded.Dose delivery accuracy was measured on the ArcCHECK system with MultiPlug accessory (SunNuclear).
Results: All plans were generated with limited planner input. Target coverage, dose homogeneity and OAR constraints were achieved “per protocol� with no plan being in the “variation acceptable� bracket. The volume of PTV receiving the prescription dose (mean ± st dev) was 95.7±0.7%. A significantly lower D2% (dose to the hottest 2% of PTV) of 32.5±0.4Gy was achieved compared to 37.5Gy allowed per protocol. Also, D98% (dose to 98% of PTV) was increased from the allowed 25Gy to 29.1±0.3Gy. The hippocampi D100% mean value was 8.7±0.2Gy and maximum dose was 15.5±0.3Gy. The average monitor units (MU) and treatment time were 830 (range 776-891MU) and 4.2 minutes (range 4.0-4.4 min). QA plans had more than 99% gamma passing rate for 2%/2mm criteria.
Conclusion: HyperArc technology could be successfully used for HA-WBRT. The efficient treatment planning with limited user input yields consistent quality plans without time consuming planning process. The automated delivery allows a complex treatment to be delivered safely in a shorter time.
Funding Support, Disclosures, and Conflict of Interest: Research funding from Varian Medical Systems.
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