DS10 - Défi des autres savoirs

Velocity map IMAGing of emitted Electrons from Radiosensitizers upon Ion collision – IMAGERI

Submission summary

Ion beam therapy, unlike conventional radiotherapy, allows a proper localization of the energy deposition in tumors and thus spares the surrounding healthy organs. Recently, the use of radiosensitizers, including high-Z nanoparticles (Ag, Au, Gd), was proposed to enhance the effects of ionizing radiation. The mechanism responsible for such an efficiency enhancement is the important release of electrons from the nanoparticles (NPs) triggered either by the primary ion beam or by secondary charged particles created along the track. These electrons may then interact directly with biomolecules. Even at low energy (below ionization threshold), electrons can induce molecular damage via Dissociative Electron Attachment (DEA). They can also produce highly reactive species such as hydroxyl radicals (OH) from the surrounding water molecules via radiolysis or DEA.

Within the IMAGERI project, we propose to quantify this low energy electron emission by providing doubly differential absolute cross sections in order to shed light on the physical processes responsible for the enhancement effect of radiosensitizers in ion beam therapy.

Therefore a new experimental set-up dedicated to the measurement of absolute cross-sections for electron emission from size-controlled isolated NPs after ion irradiation will be built. The collimated beam of metallic NPs formed using an aerodynamic lens will cross orthogonally the projectile ion beam produced by the GANIL beamlines. Emitted electrons will be extracted and analyzed in energy and angle by a velocity map imaging (VMI) spectrometer. By monitoring the target density, projectile ion beam intensity and the beams overlap with the use of a quartz crystal microbalance and an ion beam profiler, we will be able to estimate absolute cross sections for electron emission. Such cross sections will be measured and compared for various size (from nm to few tenths of nm) and elements (Ag, Au, Pt and Gd) of the NPs. Furthermore, typical ion beam kinetic energies of the Bragg-peak (MeV) and of secondary particles (keV) will be investigated.

This project aims to better understand the intrinsic properties of NPs under irradiation and the physical processes leading to the efficiency enhancement of radiation damage. It will provide data from which a broad scientific community will benefit: from experimental and theoretical physics to chemistry and biology. Absolute cross sections will be used as benchmark measurements for theory and input in Monte-Carlo computational modeling of the passage of charged particles through matter (such as GEANT4-DNA). Comparative studies between different radiosensitizers may also trigger new experiments in radiobiology. In the long run, it can impact the society as a better understanding of the fundamental processes can lead to an optimization in the choice of radiosensitizers to make ion beam therapy techniques more efficient.

Project coordination

Violaine VIZCAINO Violaine (Centre de recherche sur les ions, les materiaux et la photonique)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CIMAP Centre de recherche sur les ions, les materiaux et la photonique

Help of the ANR 278,748 euros
Beginning and duration of the scientific project: September 2016 - 36 Months

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