Characterization of Ultra-High-Dose Rate Electron Beams with ElectronFlash Linac

Abstract

Purpose: The electron linac ElectronFlash installed at Institut Curie (Orsay, France) is entirely dedicated to FLASH irradiation for radiobiological and pre-clinical studies. The system was designed to deliver an ultra-high-dose rate per pulse (UHDR) (above 106 Gy/s) and a very high average dose rate at different energies and pulse durations. A campaign of tests and measurements was performed to obtain a full reliable characterizations of the electron beam and of the delivered dose, which are necessary to the radiobiological experiments. Methods: A Faraday cup was used to measure the electron charges in a single RF pulse. The percentage depth dose (PDD) and the transverse dose profiles, at the energies of 5 MeV and 7 MeV, were evaluated employing Gafchromic films EBT-XD for two Poly-methylmethacrylate (PMMA) applicators with irradiation sizes of 30 mm and 120 mm, normally used for in vivo and in vitro experiments, respectively. The results were compared with Monte Carlo (MC) simulations. Results: The measurements were performed during a period of a few months in which the experimental set up was adapted and tuned in order to characterize the electron beam parameters and the values of delivered doses before the radiobiological experiments. The measurements showed that the dose parameters, obtained at the energy of 5 MeV and 7 MeV with different applicators, fulfill the FLASH regime, with a maximum value of an average dose rate of 4750 Gy/s, a maximum dose per pulse of 19 Gy and an instantaneous dose rate up to 4.75 ×106 Gy/s. By means of the PMMA applicators, a very good flatness of the dose profiles was obtained at the cost of a reduced total current. The flatness of the large field is reliable and reproducible in radiobiological experiments. The measured PDD and dose profiles are in good agreement with Monte Carlo simulations with more than 95% of the gamma-index under the thresholds of 3 mm/3%. Conclusions: The results show that the system can provide UHDR pulses totally satisfying the FLASH requirements with very good performances in terms of beam profile flatness for any size of the fields. The monitoring of electron beams and the measurement of the dose parameters played an important role in the in vivo and in vitro irradiation experiments performed at the Institut Curie laboratory.

FLASH Radiation Therapy — Key physical irradiation parameters and beam characteristics

“…Thus, because of a number of factors, including a shorter irradiation time, higher curative doses than CONV-RT, and a differential effect between normal tissue and tumor that will be justified by several main hypotheses, this promising strategy has garnered the interest of many researchers [14,18,20]. The next section of this review study will go into great length on these hypotheses.…”

“…x-rays [33,34], and protons beams [1,21,[35][36][37][38]. Accelerator communities such as Electron-Linac (E-Linac) can produce the required dose rate for both types of FLASH-electrons [14,26]. The pulsed irradiation of the accelerators produces high-frequency microwaves at different intervals.…”

“…To address this problem, a new technology of RT known as FLASH Radiation Therapy (FLASH-RT) as an emerging technique in RT gained much interest [2,[5][6][7][8]. In FLASH-RT, tumor and surrounding tissues receive an ultra-high-dose-rate in a fraction of a second [13][14][15][16]. With the new radiation therapy technology, it is now possible to spare normal tissue while still effectively treating malignant cells [14,[17][18][19][20].…”

“…In FLASH-RT, tumor and surrounding tissues receive an ultra-high-dose-rate in a fraction of a second [13][14][15][16]. With the new radiation therapy technology, it is now possible to spare normal tissue while still effectively treating malignant cells [14,[17][18][19][20]. In FLASH-RT, normal tissue sparing refers to the ability to deliver adequate radiation to the tumor cells while minimizing exposure to neighboring non-tumor organs [1,20].…”

Design and Test of C-band Linac Prototypes for Electron FLASH Radiotherapy

“…However, further research is needed to understand the benefits and limitations of this methodology fully and to determine the best use cases for its application in clinical settings. Currently, only a few dedicated electrons linacs are employed for experimental research [6,7,8,9,10,11,12,13], ongoing studies and technological advancements aim to make these linacs more compact and cost-effective for highenergy electrons. The ultimate goal is to use these linacs to treat deep tumors with FLASH radiotherapy in the future.…”