J Morin, JF Cabana, M Goulet*, D Theriault, CISSS - Chaudiere-Appalaches, Levis, QC, Canada

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  M Goulet

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TH-F-TRACK 6-5 (Thursday, 7/29/2021) 4:30 PM - 5:30 PM [Eastern Time (GMT-4)]

Purpose: Plastic scintillation detectors (PSDs) have advantageous dosimetric properties, including small size and energy independence, which make them ideal candidates for small field dosimetry. This work aims to quantify the performance of the HYPERSCINT RP200 (Medscint inc., Quebec city, Canada) in the process of beam modelisation for a small field stereotactic radiosurgery (SRS) program.

Methods: Dose profiles, percent depth doses and output factors were acquired as part of the commissioning of a 10MV FFF field on a VersaHD linear accelerator (Elekta). These measurements were carried out using a HYPERSCINT RP200, a Razor diode (IBA), GafChromic EBT3 films (Ashland), an Advanced Markus parallel plate ion chamber (PTW), an Exradin A26 cylindical ion chamber and an Exradin A1SL cylindrical ion chamber (Standard Imaging). Comparisons between each detector were made using percentage differences and distance to agreement criteria.

Results: Better than 0.3 gamma index (1%/1mm) was achieved between the HYPERSCINT RP200, the Razor diodes and the GafChromic EBT3 film in small field dose profiles. Lower than 0.5% dose difference was met between the PSD and the Advanced Markus in percent depth doses. Smaller than 2% agreement was achieved when comparing output factors from the RP200 and every other detectors. Average differences ± standard deviations from output factors measurements were as follow: Razor Diode: (1.1 ± 0.4)%; GafChromic films: (0.8 ± 1.1)%; A26 ion chamber: (0.3 ± 0.3)%; A1SL ion chamber: (0.5 ± 0.4)%).

Conclusion: These results demonstrate the capability of the HYPERSCINT RP200 to perform accurate small field dosimetry and beam data acquisition. This versatility in profiles, PDDs and output factor acquisition would allow for significant time savings during the commissioning process of small radiation fields. In the author’s institution, the 10MV FFF beam modelisation for SRS was entirely performed using data from this PSD detector.

Handouts

Keywords

Commissioning, Stereotactic Radiosurgery, Dosimetry

Taxonomy

TH- External Beam- Photons: Small field experimental dosimetry

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