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Evaluation of the Response of EBT3, EBT-XD, MD-V3, and HD-V2 GafChromic Films in Proton FLASH Fields

A Darafsheh1, Y Hao1, D Owen2, T Zwart2, M Wagner2, T Zhao1*, (1) Washington University School of Medicine in St. Louis, St. Louis, MO, (2) Mevion Medical Systems, Littleton, MA

Presentations

SU-H400-IePD-F4-3 (Sunday, 7/10/2022) 4:00 PM - 4:30 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 4

Purpose: FLASH radiotherapy at ultra-high dose rates (>40 Gy/s) can potentially better spare healthy tissues compared to that at conventional dose rates (~0.1 Gy/s), while maintaining high tumor control probability. The purpose of this work is to study the response of different radiochromic film models in FLASH and conventional proton radiation fields.

Methods: GafChromic™ EBT3, EBT-XD, and MD-V2 film models were studied in this work. Film pieces were irradiated using a Mevion HYPERSCAN synchrocyclotron at ultra-high dose rate (75 Gy/s) and conventional dose rate (0.5 Gy/s). Films were placed at depth of 0.5 cm in tissue-mimicking plastics and irradiated with a proton beam with 2.6 cm range. Another 1 cm phantom was placed behind the film sample. A faraday cup was placed after the phantoms to assure that the same dose has been delivered to the films. Two dose levels (5 Gy and 30 Gy) were studied in this work. The optical density (OD) of the films were measured using a flatbed scanner 48 hours after irradiation.

Results: No significant difference, within the uncertainty of the measurements, was observed between the optical density of the films received the same dose at FLASH and conventional dose rate.

Conclusion: The response of EBT3, EBT-XD, MD-V3, and HD-V2 GafChromic™ films showed to be independent of the dose rate within the dose levels and dose rates studied in this work. Among these models, EBT-XD was found to be more suitable for FLASH RT dosimetry in terms of the dynamic range.

Funding Support, Disclosures, and Conflict of Interest: Daniel R. Owen, Townsend Zwart, and Miles Wagner are employees of Mevion Medical Systems.

Keywords

Film, Dosimetry, Protons

Taxonomy

TH- External Beam- Particle/high LET therapy: Proton therapy – Development (new technology and techniques)

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