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  4. Evaluation of a Plastic Scintillation Detector for Commissioning Data Acquisition in An MR-Guided Linear Accelerator

Evaluation of a Plastic Scintillation Detector for Commissioning Data Acquisition in An MR-Guided Linear Accelerator

B Barraclough*, K Mittauer , D Jacqmin , A Antolak , P Yadav , University of Wisconsin, Madison, WI

Presentations

(Tuesday, 7/16/2019) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 4

Purpose: Standard Imaging’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 ViewRay’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 ViewRay’s daily QA phantom. W2 response linearity with MU was also measured. Profiles, PDDs, and OFs were calculated with ViewRay’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.

Keywords

Scintillators, MR, Radiation Detectors

Taxonomy

TH- Radiation dose measurement devices: scintillators

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