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Vienna, Austria

ESTRO 2023

Session Item

Optimisation, algorithms and applications for photon and electron treatment planning
Poster (Digital)
Physics
Development of a TPS for Very High Energy Electrons delivered at FLASH rates
Annalisa Muscato, Italy
PO-2031

Abstract

Development of a TPS for Very High Energy Electrons delivered at FLASH rates
Authors:

Angelica De Gregorio1, Daniele Carlotti2,3, Marta Fischetti4,5, Gaia Franciosini6,7, Michela Marafini7,8, Ilaria Mattei9, Annalisa Muscato10,7, Alessio Sarti4,7, Angelo Schiavi4,7, Adalberto Sciubba4, Marco Toppi4, Giacomo Traini7, Antonio Trigilio6,7, Vincenzo Patera7,4

1University La Sapienza, Rome, Department of Physics , Rome, Italy; 2University La Sapienza, Rome, Department of Physics, Rome, Italy; 3Fondazione Policlinico Universitatio Campus-Bio Medico, Department of Operative Research Unit of Radiation Oncology, Rome, Italy; 4University La Sapienza of Rome, Department of Scienze di Base e Applicate per l’Ingegneria, Rome, Italy; 5INFN, Istituto Nazionale di Fisica Nucleare , Section of Roma 1, Rome, Italy; 6University La Sapienza of Rome, Department of Physics, Rome, Italy; 7INFN, Istituto Nazionale di Fisica Nucleare, Section of Roma 1, Rome, Italy; 8Museo Storico della Fisica e Centro Studi e Ricerche “E.Fermi”, -, Rome, Italy; 9INFN, Istituto Nazionale di Fisica Nucleare, Section of Milan, Milan, Italy; 10University La Sapienza of Rome, Department of Dipartimento di Scienze e Biotecnologie medico-chirurgiche, Rome, Italy

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Purpose or Objective

Very High Energy Electron (VHEE) beams (E> 50 MeV) have been explored in the past for the treatment of deep-seated tumors, considering their characteristic dose release that allows a better sparing of Organ at Risk with respect to conventional radiotherapy (RT). The availability of VHEE in clinical centers, hampered in the past by the beam production and delivery system complexity is currently being investigated in view of the recent developments in the field of electrons acceleration. In addition, several pre-clinical studies recently claimed that the toxicity in healthy tissues can be significantly reduced, while keeping the same efficacy in cancer killing, if the dose rate is radically increased (∼50 Gy/s) with respect to conventional treatments (∼0.01 Gy/s). Such effect is known as the FLASH effect. To investigate the potential of VHEE based RT, a VHEE Treatment Planning System (TPS) which include the evaluation of volumetric constraints is needed: once the beam model and the patient information is defined, the delivery parameters (such as position, energy and current of the electron beams) can be computed optimizing the absorbed dose maps.

Material and Methods

With the aim of selecting the energy and the intensity of the electron beams, the TPS takes as input the dose maps generated by MC simulations performed with the FRED software for a given set of conditions: unit fluence, pre-defined energy and defined point of access inside the patient body. The goal is to minimize the cost function, which quantifies the degree to which a treatment plan meets its competing objectives, by modifying the dose distribution within the constraints of clinical deliverability. Minimization methods based on the Simulated Annealing and the Quantum Simulated Annealing algorithms are used, allowing to take into account more complex volumetric and dose-rate constraints. The minimization output are the optimized dose map of the patient and the corresponding values for each particle beam that the accelerator has to deliver.

Results

The tumor coverage and the dose absorbed by the organs at risk have been analyzed by means of Dose Volume Histograms for the case of a Head&Neck treatment. The comparison of the achieved results with the real proton therapy plan and the simulation of a conventional RT treatments has been performed. The results show that the plan optimized with the VHEE FLASH TPS is competitive with standard RT, and that it could allow a better sparing of the healthy tissues.

Conclusion

In this contribution the development of a TPS for VHEE treatments delivered at FLASH rates is presented: the obtained results show that the implemented algorithms allow to obtain electron plans compatible with standard TPS solutions and  are suitable for the VHEE FLASH potential studies in which also the beam delivery strategy can be optimized.