ESTRO 2024 - Abstract Book

S3224

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

916

Mini-Oral

Dosimetric characterization of the FLASHKNiFE 10 MeV UHDR beam towards clinical translation

Julie Colnot 1,2,3 , Cathyanne Schott 2,3 , Imane Saïd-Mansour 2,3 , Thibault Dijoud 1 , Mario Caliendo 4 , Maud Couturier 1 , Raphaël Moeckli 5 , Jean-François Germond 5 , Reiner Geyer 5 , Christoph Bert 6 , Maya Shariff 6 , Esmeralda Poli 7 , Nathalie Fournier-Bidoz 3 , Daphné Morel 2 , Eric Deutsch 2,3 , Charlotte Robert 2,3 1 THERYQ, THERYQ, Peynier, France. 2 Gustave Roussy, INSERM U1030, Villejuif, France. 3 Gustave Roussy, Radiotherapy Department, Villejuif, France. 4 PMB-ALCEN, PMB-ALCEN, Peynier, France. 5 Lausanne University Hospital and Lausanne University, Institute of Radiation Physics, Lausanne, Switzerland. 6 Universitätsklinikum, Radiotherapy Department, Erlangen, Germany. 7 Santa Maria Hospital, Radiotherapy Department, Lisbon, Portugal

Purpose/Objective:

Radiation therapy (RT) delivered at ultra-high dose rate (UHDR), referred as FLASH RT, demonstrated normal tissue sparing while maintaining tumor control in several preclinical studies. This new modality is on the way of clinical translation with dedicated commercial FLASH systems. In this context, this work evaluates the dosimetric performance of the 10 MeV electron UHDR beam of the FLASH radiotherapy system FLASHKNiFE (THERYQ), towards its clinical commissioning at Gustave Roussy hospital as part of a European project funded by EIT Health.

Material/Methods:

The FLASHKNiFE system delivers pulsed UHDR electron beams (> 100 Gy/s, 6-10 MeV) and is dedicated to superficial radiotherapy and intra-operative radiotherapy. The time structure of the generated UHDR beams can be customized by the user by modifying the pulse rate frequency (PRF, 10-250 Hz) and the pulse width (PW, 0.5-4 µs) on the interface. Given the sparse literature on how to characterize the performance of this extreme dose delivery system, evaluation tests and tolerances were adapted in this work from the recommendations of the international standards IEC 60976 and IEC 60977[1-2] to account for the specific aspects of UHDR delivery. The tests performed on the 10 MeV UHDR beam configuration included repeatability on consecutive irradiations for different UHDR parameters, short-term stability of output and energy, percent depth dose, cross profiles, dose per pulse and linearity for various UHDR parameter combinations. The energy follow-up was performed using an energy indicator corresponding to the ratio of the dose measured at the depth of maximum dose and at twice this depth. This beam characterization was achieved by means of dosimeters with documented independent response with dose rate: radiochromic films (EBT3, Ashland)[3] and the FlashDiamond detector (PTW)[4], in water-equivalent plastic slabs under reference conditions.

Results:

The results obtained with the two dosimeters were consistent within reported uncertainties in this study. Regarding the FLASHKNiFE beam performances, after a daily warm-up, the output repeatability of the UHDR 10 MeV beam proved to be better than 0.5% for the different settings tested up to the extreme PW and PRF. The delivered dose was also proportional to the number of pulses within 2% for these same combinations. The output stability over 4