Room: Exhibit Hall | Forum 4
Purpose: Standard Imagingâ€™s new Exradin W2 scintillator has not yet been well-characterized in the literature. The small active volume (1mm diameter, 1mm length) and nearly-water-equivalent material of a plastic scintillator make it attractive for small field measurements. This work characterized the response of the detector and explored the challenges in using this detector for ViewRayâ€™s 0.345T MR-guided MRIdian linac system.
Methods: Initial Cerenkov light ratio (CLR) calibration was performed. Profiles and PDDs were measured in a 1D water tank with an ion chamber (IC), EDGE diode, and W2 scintillator. Output factors (OFs) were measured with film in solid water and diode and W2 in a water tank. Angular dependence of the IC and W2 were measured with ViewRayâ€™s daily QA phantom. W2 response linearity with MU was also measured. Profiles, PDDs, and OFs were calculated with ViewRayâ€™s Monte Carlo treatment planning system (TPS) for further comparison. The W2 CLR calibration was investigated to determine reproducibility through a measurement session, from day to day, and from one delivery system to another (TrueBeam vs Viewray).
Results: Outside of the buildup region, W2-measured PDDs were within 1% of measurement and 1.7% of TPS. Profiles passed a 1%/1mm gamma comparison. W2 OFs were within 1% of film, 2% of diode, and 1.6% of TPS for all field sizes. Angular dependence was within 3%. Above 5 MU, MU linearity was within 0.3%. CLR calibration maintained detector response within 1% through a session and 2% day-to-day but showed >15% difference between delivery systems.
Conclusion: The new W2 scintillator has excellent performance gathering a range of data for 0.345T MR-guided linacs. If proper calibration procedures are followed, this detector has close agreement with well-characterized ICs, diodes, and film.
Funding Support, Disclosures, and Conflict of Interest: Dr Mittauer reports personal fees and consulting fees from ViewRay Inc. during conduct of this study.