ESTRO 2024 - Abstract Book

S3394

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

[7] Nailon WH, Welsh D, McDonald K, Burns D, Forsyth J, Cooke G, et al. EPID-based in vivo dosimetry using Dosimetry CheckTM: Overview and clinical experience in a 5-yr study including breast, lung, prostate, and head and neck cancer patients. J Appl Clin Med Phys 2019;20:6–16. https://doi.org/10.1002/acm2.12441.

[8] Dogan N, Mijnheer BJ, Padgett K, Nalichowski A, Wu C, Nyflot MJ, et al. AAPM Task Group Report 307: Use of EPIDs for Patient-Specific IMRT and VMAT QA. Med Phys 2023;50:e865–903. https://doi.org/10.1002/mp.16536.

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Digital Poster

ELF-DORADO – First comparison data on two UHDR ElectronFlash systems

Alessia Gasparini 1,2 , Verdi Vanreusel 2,3 , Valentina Aviles 4 , Luana De Freitas Nascimento 3 , Dirk Verellen 1,2 , Sophie Heinrich 5 1 Iridium, Radiotherapy, Wilrijk, Belgium. 2 University of Antwerp, CORE, Wilrijk, Belgium. 3 SCK CEN, RDA, Mol, Belgium. 4 Universidad Nacional de Colombia, Facultad de Ciencias, Bogota, Colombia. 5 Institut Curie, U1021/UMR3347, Orsay, France

Purpose/Objective:

FLASH radiotherapy uses ultra-high dose rates (UHDR >40 Gy/s) over a very short time period (<100 ms). Acceptance procedures for high dose rate systems are not standard and dosimetry is challenging. The challenge of FLASH dosimetry and Quality Assessment is to characterize an entirely novel equipment operating in ultra-high dose-rate with unknown output, using instruments and methods that still have to be validated in these extreme conditions.Only developing common procedures and performing multiple cross-comparisons will provide the accuracy that is required for reliable preclinical studies on FLASH effect.

Material/Methods:

The comparison tests were performed on two similar units of a dedicated research linac for Flash radiotherapy with electron (ElectronFlash, SIT, Italy). Unit1 (Institut Curie) and unit2 (Iridium/GZA) are directly tunable for beam energy, pulse length, pulse repetition frequency (PRF), field size, and distance from the source, in conventional and UHDR delivery modality. The two systems provide currently a very similar output, the main differences are the available energies (5 and 7 MeV in Institut Curie and 7 and 9 MeV at Iridium) and partially the monitoring system for the output beam. The UHDR beam output in monitored by two toroidal inductors (1), and this is read out by an internal system and a Wavesurfer 4054HD scope (Teledyne Lecroy, US). We used two newly flashDiamond (fD) detectors (2) and two Unidose Webline electrometers, both from PTW, Germany. External boxes were provided by PTW to avoid instantaneous currents exceeding the specifications of the electrometer. Measurements were performed in RW3 and PMMA slabs, using the fD holder and a self-designed holder, respectively.

Results: