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Characterization of the Hyperscint Dosimetry System for Real-Time Dosimetry Measurements with the Varian TrueBeamLinac

C Penner1,2*, C Hoehr2, C Mendez1, C Duzenli1, (1) BC Cancer, Vancouver, BC, CA, (2) TRIUMF, Vancouver, BC, CA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Plastic scintillator/optical fibre dosimetry systems are advantageous due to their near water equivalence, waterproof construction, linear dose response, and good spatial resolution due to their small size. The nanosecond decay times of plastic scintillators enable the possibility of real-time dosimetry. We tested the new Hyperscint?? fibre detector system to determine if, in addition to the expected dose and field size responses, this system can provide real-time dose information.

Methods: The Hyperscint?? system incorporates a specialized spectrometer optimized for radiation dosimetry coupled to PMMA fibre and plastic scintillators customized to the application. A 3 mm plastic scintillator detector was used in this study. Tests were performed with the centre of the probe at the isocentre of a Truebeam?? 6 MV radiotherapy field under standard reference dose conditions. Dose, dose rate and field size dependence were measured. Timing studies were done by decreasing the integration times from 5 s down to 0.1 s and delivering 200 MU for each.

Results: The Hyperscint?? system exhibits a linear dose response and measures relative dose and dose rates to within 1% and 3% of expected respectively. As field size was increased from 9 cm² to 625 cm² the Hyperscint??’s relative dose measurements were within 2.5%, when normalized to the 10 x 10 field, of the doses delivered. Furthermore, while integration times were decreased, down to 0.3 s integration yielded under 1% discrepancy when measurements were normalized, and under 3 % discrepancy at 0.1 s.

Conclusion: The Hyperscint?? system is suitable after appropriate calibration to be used to measure relative dose delivered in cGy as well as indicate changing dose conditions within 0.3 seconds. Further studies will be pursued to ensure repeatability of results, test its capability for absolute dosimetry and investigate the Hyperscint??’s potential for dose verification with the VERO?? markerless motion-tracked delivery system.

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Keywords

Scintillators, Dosimetry

Taxonomy

TH- Radiation Dose Measurement Devices: optical/photoacoustic/Cerenkov dosimetry

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