ESTRO 2024 - Abstract Book

S3737

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

3245

Poster Discussion

Design and characterization of an electron minibeam/UHDR facility for radiobiological experiments

Francesco Romano 1,2 , Jake Harold Pensavalle 3,4,5 , Maria Grazia Celentano 3,5 , Damiano Del Sarto 3,5 , Giuseppe Felici 4 , Gaia Franciosini 6 , Luigi Masturzo 3,4,5 , Vincenzo Patera 6 , Yolanda Prezado 7 , Giuliana Milluzzo 1 , Fabio Di Martino 3,5,8 1 Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Catania, Italy. 2 University Medical Centre Groningen, PARTREC, Groningen, Italy. 3 Centro Pisano Multidisciplinare sulla Ricerca e Implementazione Clinica della Flash Radiotherapy, Centro Pisano Multidisciplinare sulla Ricerca e Implementazione Clinica della Flash Radiotherapy, Pisa, Italy. 4 Sordina IORT Technologies S.p.A., 2Sordina IOResearch and development, Aprilia, Italy. 5 University of Pisa, Physics Department, Pisa, Italy. 6 Sapienza Università di Roma, 6Dipartimento di Fisica, Roma, Italy. 7 7Université Paris-Saclay, CNRS UMR3347, Signalisation Radiobiologie et Cancer, Orsay, France. 8 Azienda Ospedaliero Universitaria Pisa (AOUP), 8Azienda Ospedaliero U Fisica Sanitaria, Pisa, Italy The Mini Beam Radiotherapy (MBRT), making use of sub-millimetric parallel beams (0.5-1 mm) spaced in 1-3 mm, has recently gained renovated interest thanks to the observed reduced toxicity in the healthy tissues while maintaining or enhancing the tumor control. Recently, FLASH radiotherapy is also attracting as increasing interest as, also for the FLASH effect, the possibility of widening the therapeutic window was shown thanks to a better sparing of healthy tissues still keeping the same effects on the cancerous cells. However, the biological mechanisms that could explain the minibeam and the FLASH effect are both still unknown, although a few hypothesis are being explored. On this concern, the investigation of possible correlations between the two effects, including possible synergistic effects could play an important role in contributing to understanding key aspects behind the biological mechanisms and in further optimizing the sparing of the healthy tissues. Therefore, the possibility of combining Ultra High Dose Rates (UHDR) and minibeams could represent a significative step forward towards the overall understanding of such innovative radiotherapy techniques and to explore and exploit possible synergistic effects. A facility dedicated to the production of low energy UHDR electron minibeams was recently dosimetrically characterized in the perspective of preclinical studies to investigate both the FLASH and minibeam effects and any possible combination of them. An ElectronFLASH LINAC able to accelerate 7 and 9 MeV UHDR electron beams with variable dose rate from cGy/s up to 5 MGy/s and a beam diameter from 1 cm up to 10 cm is in operation for over one year. The nozzle of the accelerator was customized in order to produce electron minibeams still preserving UHDRs, necessary to trigger also the FLASH effect. This was obtained realizing different configurations of tungsten passive collimators, previously designed through Monte Carlo simulations, which produce minibeams with 1 and 2 mm size (FWHM) and spaced up to 3 mm (Figure 1), also including grid (hole collimators) and planar (linear collimators) geometries. A systematic dosimetric characterization was performed by using Radiochromic films, which allow for both high spatial and UHDR independent spatial dose distribution measurements. Purpose/Objective: Material/Methods:

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