Institut Curie
Essone
Medical physicist. Currently working in Institut Curie research team devoted to FLASH basic and preclinical studies.

Presenter Of 1 Presentation

MONITORING A FLASH BEAM: FOR PRECLINICAL STUDIES AND TOWARDS CLINICAL APPLICATIONS

Session Type
FLASH Modalities Track (Oral Presentations)
Date
Wed, 01.12.2021
Session Time
10:20 - 11:30
Room
Room 2.31
Lecture Time
10:30 - 10:40

Abstract

Background and Aims

With medical linear accelerators, the dose is delivered in approximately a thousand of low-dose radiation pulses and is regulated by monitoring ionization chambers, which turn off the beam once the preset number of Monitor Units (MU) is reached. In FLASH electron beams, on the contrary, the dose-per-pulse is much higher (> 1 Gy/pulse), which, a) prevent the use of conventional monitoring systems, and b) implies that the complete treatment is delivered with a very limited number of pulses, sometimes only one. To guarantee that the planned dose is delivered as intended, new methodologies for monitoring must be elaborated for FLASH beam delivery.

Methods

In preclinical studies with ElectronFLASH4000 (SIT), we have defined FLASH-MU as a fraction of the pulse’s temporal profile integral, which is recorded with a non-destructive monitoring toroid. For the control experiments performed at conventional dose-rate, MU measured by classical monitor chambers have been cross-referenced with FLASH-MU, through calibration by film dosimetry.

Results

FLASH electron beams can be effectively monitored by toroidal current transformers, provided they have adequate performances. Prescribed doses have been translated in MU with different pulse length, pulse amplitude and/or number of pulses. Heterogeneous pulse sequences including decreasing doses-per-pulse allowed a smaller cut-off step.

Conclusions

This opens the discussion on techniques for FLASH monitoring and on beam cut-off strategies for radiotherapy treatments delivered with very few ultra-high-dose pulses. At least some of them can already be tested for dose accuracy and biological effectiveness.

Acknowledgement: This work is part of 18HLT04-UHDpulse project, which received funding from the EMPIR program.

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Author Of 4 Presentations

MONITORING A FLASH BEAM: FOR PRECLINICAL STUDIES AND TOWARDS CLINICAL APPLICATIONS

Session Type
FLASH Modalities Track (Oral Presentations)
Date
Wed, 01.12.2021
Session Time
10:20 - 11:30
Room
Room 2.31
Lecture Time
10:30 - 10:40

Abstract

Background and Aims

With medical linear accelerators, the dose is delivered in approximately a thousand of low-dose radiation pulses and is regulated by monitoring ionization chambers, which turn off the beam once the preset number of Monitor Units (MU) is reached. In FLASH electron beams, on the contrary, the dose-per-pulse is much higher (> 1 Gy/pulse), which, a) prevent the use of conventional monitoring systems, and b) implies that the complete treatment is delivered with a very limited number of pulses, sometimes only one. To guarantee that the planned dose is delivered as intended, new methodologies for monitoring must be elaborated for FLASH beam delivery.

Methods

In preclinical studies with ElectronFLASH4000 (SIT), we have defined FLASH-MU as a fraction of the pulse’s temporal profile integral, which is recorded with a non-destructive monitoring toroid. For the control experiments performed at conventional dose-rate, MU measured by classical monitor chambers have been cross-referenced with FLASH-MU, through calibration by film dosimetry.

Results

FLASH electron beams can be effectively monitored by toroidal current transformers, provided they have adequate performances. Prescribed doses have been translated in MU with different pulse length, pulse amplitude and/or number of pulses. Heterogeneous pulse sequences including decreasing doses-per-pulse allowed a smaller cut-off step.

Conclusions

This opens the discussion on techniques for FLASH monitoring and on beam cut-off strategies for radiotherapy treatments delivered with very few ultra-high-dose pulses. At least some of them can already be tested for dose accuracy and biological effectiveness.

Acknowledgement: This work is part of 18HLT04-UHDpulse project, which received funding from the EMPIR program.

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OVERVIEW AND CURRENT STATUS OF THE JOINT RESEARCH PROJECT UHDPULSE - “METROLOGY FOR ADVANCED RADIOTHERAPY USING PARTICLE BEAMS WITH ULTRA-HIGH PULSE DOSE RATES”

Session Type
FLASH Modalities Track (Oral Presentations)
Date
Wed, 01.12.2021
Session Time
14:50 - 15:50
Room
Room 2.15
Lecture Time
14:50 - 15:00

Abstract

Background and Aims

Dosimetry for FLASH radiotherapy, VHEE radiotherapy as well as for laser-driven beams cause significant metrological challenges due to the ultra-high dose rates and pulsed structure of these beams, in particular for real time measurements with active dosimeters. It is not possible to simply apply existing Codes of Practice available for dosimetry in conventional external radiotherapy here. However, reliable standardized dosimetry is necessary for accurate comparisons in radiobiological experiments, to compare the efficacy of these new radiotherapy techniques and to enable safe clinical application. UHDpulse aims to develop the metrological tools needed for reliable real-time absorbed dose measurements of electron and proton beams with ultra-high dose rate, ultra-high dose per pulse or ultra-short pulse duration.

Methods

Within UHDpulse, primary and secondary absorbed dose standards and reference dosimetry methods are developed, the responses of available state-of-the-art detector systems are characterised, novel and custom-built active dosimetric systems and beam monitoring systems are designed, and methods for relative dosimetry and for the characterization of stray radiation are investigated.

Results

Prototypes of different active dosimetry systems show promising results for real-time dosimetry for particle beams with ultra-high pulse dose rates. The results of the UHDpulse project will be the input data for future Codes of Practice.

Conclusions

A brief overview of the progress in the UHDpulse project and the involved institutions will be given.

Acknowledgement: This project 18HLT04 UHDpulse has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme.

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PERSPECTIVES IN LINEAR ACCELERATOR FOR FLASH VHEE : STUDY OF A COMPACT C BAND SYSTEM

Session Type
FLASH Modalities Track (Oral Presentations)
Date
Thu, 02.12.2021
Session Time
11:00 - 12:00
Room
Hall C
Lecture Time
11:20 - 11:30

Abstract

Background and Aims

In order to translate the FLASH effect in clinical use and to treat deep tumors, Very High Electron Energy irradiations could represent a valid technique. Here, we address the main issues in the design of a VHEE FLASH machine. We present preliminary results for a compact C-band system aiming to reach a high accelerating gradient and high current necessary to deliver a dose up to 12 Gy/pulse, with a beam pulse duration of 3

Methods

The proposed system is composed by low energy high current injector linac followed by a high acceleration gradient structure able to reach 50-100 MeV energy range. To obtain the maximum energy, an energy pulse compressor options is considered. CST code was used to define the specifications RF parameters of the linac. To optimize the accelerated current and therefore the delivered dose, beam dynamics simulations was performed using Parmela code.

Results

The VHEE parameters Linac suitable to satisfy FLASH criteria were simulated. Preliminary results allow to obtain a maximum energy of 100 MeV, with a peak current of 200 mA, which corresponds to a charge of 200 nC per μs, or equivalently to about 4 Gy in a single pulse of 1µs and >106 Gy/s over a ∅10 cm irradiation surface.

Conclusions

A promising preliminary design of VHEE linac for FLASH RT has been performed. Supplementary studies are ongoing to complete the characterization of the machine and to manufacture and test the RF prototypes.

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NEW MODELS FOR FLASH STUDIES.

Session Type
FLASH Mechanisms Track (Oral Presentations)
Date
Thu, 02.12.2021
Session Time
15:10 - 16:10
Room
Room 2.15
Lecture Time
15:10 - 15:20

Abstract

Background and Aims

Currently, many research groups are more interested in the FLASH radiotherapy characterized by irradiation with ultra-high dose rate. A first usual step is to validate the beam line for FLASH studies by reproducing published FLASH effect in animals. However, it classically requires time consuming animal studies with dedicated skills, authorizations and infrastructures. Thus, to provide alternative methods and facilitate the implementation and validation of new FLASH beams, we aimed at developing in vitro and ex vivo models that will allow rapid and pertinent evaluation of the FLASH effect.

Methods

For our studies, we are using the ElectronFLASH LINAC manufactured by SIT company. To achieve this goal, we first used an in vitro model of human lung basal stem cells obtained from patients. Cultured in specific air-liquid conditions, this model allows the monitoring of stem cells survival and their capacity to differentiate after irradiation. In parallel, we adapted organotypic lung slices model, recapitulating lung complexity, architecture and microenvironment interactions, for radiation toxicity studies.

Results

Our results indicate that organotypic lung slices enables a rapid evaluation of the FLASH effect.

Conclusions

These models developed in the lab allow to rapidly determine the impact of the various beam parameters on FLASH effect with a robust and reproducible assay. With the inclusion of tumoral cells within the organotypic lung slices, we hypothesize that this ex vivo model can assess concomitantly the FLASH sparing effect on healthy tissue as well as the antitumoral efficacy. Moreover, the model can apply for human patient samples as well as rodent tissues.

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