Dose Verification for LINAC-Based Stereotactic Radiosurgery Planned at Different Prescription Isodose Levels Using Delta4 Phantom+

Background: Linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) plans and their treatment are complex techniques that require a comprehensive quality assurance program before they are clinically implemented. To cope with this intricacy, clinics must comprehensively validate treatment plans to deliver precise doses and assure patients. The study aimed to verify the treatment planning dose to the dose delivered at the LINAC during the SRS treatment planned at different prescription isodoses with the new wireless Delta4 Phantom+. Materials and Methods: Clinically accepted volumetric modulated arc therapy (VMAT) SRS plans made with the Stereotactic End-to-End Verification (STEEV) anthropomorphic phantom were created with six different prescription isodose level using 6 MV flattening filter free (FFF) beam. All these VMAT SRS plans were replicated on the Delta4 Phantom+ and delivered with Varian Truebeam LINAC. The planned and delivered dose showed excellent correlation, and this was evaluated using distance to agreement (2 mm), dose deviation (2%), and gamma-index passing rate. Results: The results showed that the calculated treatment planning system (TPS) dose and the measurement with the Delta4 Phantom+were in excellent accord. The minimum gamma pass rate was 99.6% and the maximum 100%. The gamma passing rate above 95% for all plans and dose goals were achieved. Conclusion: The verification with the Delta4 Phantom+ measurement depicted an excellent correlation with the dose of the SRS treatment plans for the different prescription isodose levels. The wireless Delta4 Phantom+ device is precise and consistent. It is a quickly set-up device, suitable for SRS treatment verification and allows for real-time measurement. However, we do recommend a stricter passing rate for VMAT SRS Plans.