Plastic and Lead-Doped Scintillators for Ultrahigh Dose-Rate Irradiations Delivered with An X-Ray Tube
D Cecchi1*, C Gigeure2, F Larose2, F Therriault-Proulx3, L Beaulieu2, M Bazalova-Carter1, (1) University of Victoria, Victoria, BC ,CA, (2) CHU de Quebec - Universite Laval, Quebec, QC,(3) MedScint, Quebec, QC, CA
Presentations
TH-C-TRACK 6-4 (Thursday, 7/29/2021) 1:00 PM - 2:00 PM [Eastern Time (GMT-4)]
Purpose: To examine the capabilities of plastic scintillators of different compositions to accurately measure dose in high dose-rate dose irradiations delivered with an x-ray tube.
Methods: The output of five 1-mm in diameter and 3-mm long scintillators of varying materials was measured in short sub-second irradiation intervals using a traditional x-ray tube equipped with an in-house rotating shutter-wheel system. The shutter system was developed to limit exposure time to the scintillator by a continuous x-ray beam. Two plastic scintillator dosimeters made of polystyrene (BCF-10 and BCF-60) and three lead-loaded scintillators (0.5%, 1.4%, and 5% concentrations) were used. Scintillator output was normalized with respect to TOPAS Monte Carlo (MC) dose calculations using 100 and 200 ms exposures at a constant tube current of 25 mA and tube voltage of 80 kVp. Output linearity was measured for irradiation times between 10-100 ms. Dose-rate independence was tested with varying tube-current between 3-37.5 mA for the 80 kVp beam. Energy dependence was tested for all the probes at tube voltages ranging between 80-120 kVp.
Results: All probes showed excellent agreement with MC for the 80 kVp beam and irradiation intervals of 100 and 200 ms. When irradiation time was varied between 10-100ms, scintillator output was shown to be linear with exposure time (R2 > 0.999) for all probes. Scintillator output was also shown to be dose-rate independent (R2 > 0.999) for all tested probes. At tube voltages higher than 80 kVp, it was shown that scintillators output exhibited some quenching, resulting in a maximum difference between experimental and MC data of 5.8% across the studied 80-120 kVp energy range for the 5% lead-loaded scintillator.
Conclusion: Plastic scintillators of different compositions have the capability to accurately measure high dose-rate irradiations delivered in short ~10 ms intervals by a conventional x-ray tube.
Funding Support, Disclosures, and Conflict of Interest: Conflict of Interest: FT-P is a founder of Medscint Funding: NSERC Discovery Grant and Canada Research Chair Program
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