Microdosimètre en diamant pour la hadronthérapie

Hadron therapy is an innovative type of radiotherapy for cancer treatment which enables tumor cells to be more effectively destroyed than by conventional radiotherapy using photons. At present, the linear energy transfer (LET) of particles is used as a fundamental parameter in predicting the relative biological effectiveness (RBE) of particle beams. However, serious limitations of the LET concept with respect to the RBE and the difference between different types of radiation have been discussed. These limitations led to the introduction of a measurable stochastic quantity called lineal energy of particles, which provides a fundamental basis for microdosimetry. Having access to such experimentally measured quantities is essential for validating simulations and models, which in turn improve the treatment efficiency. Currently, no microdosimetric detectors using the lineal energy as a measurement quantity are available on the market for routine clinical use. The objective of this PhD project was to develop a novel type of solid-state tissue-equivalent diamond-based microdosimetric system to create a state-of-the-art tool for obtaining lineal energy measurements with high spatial resolution under clinical conditions during hadron therapy. Various microfabrication techniques, such as plasma etching, thin films deposition and photolithography, were used to create diamond microdosimeter prototypes at CEA in France. The IBIC (Ion Beam Induced Charge) characterization of diamond microdosimeters was made possible by being able to conduct experiments with particle microbeams at national and international partner laboratories, such as AIFIRA CENBG in France and ANSTO in Australia. The final prototypes of the developed devices were integrated with suitable, multi-channel electronics, and their performance was tested in proton and heavy-ion medical centers at IC-CPO in France, together with HIMAC in Japan. The obtained measurements were compared with results derived from Geant4 Monte Carlo particle transport simulations and other devices developed within this field.La hadronthérapie est un traitement innovant du cancer qui permet de détruire les cellules tumorales plus efficacement que par la radiothérapie conventionnelle utilisant des photons. Actuellement, le transfert d'énergie linéique (TEL) des particules est utilisé comme paramètre pour prédire l'efficacité biologique relative (EBR) des faisceaux de particules. Cependant les limitations de l’utilisation de ce paramètre ont conduit à l'introduction d'une quantité stochastique mesurable appelée énergie linéale des particules, qui constitue la base de la microdosimétrie. La valeur mesurée expérimentalement de l’énergie linéale est essentielle pour valider les simulations et les modèles dans l’objectif d’améliorer en conséquence l'efficacité du traitement. Actuellement, aucun détecteur microdosimétrique permettant la mesure de l'énergie linéale n'est disponible pour un usage en routine clinique. L'objectif de ce projet de doctorat est de développer un nouveau type de microdosimètre à l’état solide, équivalent au tissu, à base de diamant. Ce détecteur à haute résolution spatiale doit permettre de réaliser des mesures d'énergie linéale dans des conditions cliniques pendant un traitement de hadronthérapie. Diverses techniques de microfabrication, telles que la gravure par CVD, le dépôt de couches minces et la photolithographie, ont été utilisées pour créer des prototypes de microdosimètres en diamant au CEA, en France. Plusieurs générations de microdosimètres ont été fabriquées et caractérisées par un processus itératif afin d’aboutir à une version de dosimètre la plus optimisée possible. Les caractérisations, sous microfaisceaux de particules ont été réalisées par IBIC (Ion Beam Induce Charge) sur la plateforme AIFIRA au CENBG en France et à l’ANSTO en Australie. Les prototypes finaux ont été intégrés à une électronique multicanal appropriée et leurs performances ont été testées dans des centres médicaux de proton et d'ions lourds à l'IC-CPO en France, ainsi qu'au HIMAC au Japon. Les mesures obtenues ont été comparées à celles d'autres dispositifs développés dans ce domaine ainsi qu’aux simulations obtenues avec le codes de transport de particules Monte Carlo, Geant4

Optimization of a neutron dosimeter for the high energy accelerators

In high energy accelerator facilities the neutron radiation should be continuously measured during operation to control the ambient dose. This requires a reliable neutron dosimeter in a wide energy range. In this work we present an optimization of a compact cylindrical passive neutron dosimeter for the usage in wide energy neutron fields

Optimization of a neutron dosimeter for the high energy accelerators

In high energy accelerator facilities the neutron radiation should be continuously measured during operation to control the ambient dose. This requires a reliable neutron dosimeter in a wide energy range. In this work we present an optimization of a compact cylindrical passive neutron dosimeter for the usage in wide energy neutron fields

Simultaneousmeasurements of dose and microdosimetric spectra in a clinical proton beam using a scCVD diamond membrane microdosimeter

International audienceA single crystal chemical vapor deposition (scCVD) diamond membrane-based microdosimetric system was used to perform simultaneous measurements of dose profile and microdosimetric spectra with the Y1 proton passive scattering beamline of the Center of Proton Therapy, Institute Curie in Orsay, France. To qualify the performance of the set-up in clinical conditions of hadrontherapy, the dose, dose rate and energy loss pulse-height spectra in a diamond microdosimeter were recorded at multiple points along depth of a water-equivalent plastic phantom. The dose-mean lineal energy ($\overline{y}_D$) values were computed from experimental data and compared to silicon on insulator (SOI) microdosimeter literature results. In addition, the measured dose profile, pulse height spectra and $\overline{y}_D$ values were benchmarked with a numerical simulation using TOPAS and Geant4 toolkits. These first clinical tests of a novel system confirm that diamond is a promising candidate for a tissue equivalent, radiation hard, high spatial resolution microdosimeter in beam quality assurance of proton therapy

Simultaneous Measurements of Dose and Microdosimetric Spectra in a Clinical Proton Beam Using a scCVD Diamond Membrane Microdosimeter

A single crystal chemical vapor deposition (scCVD) diamond membrane-based microdosimetric system was used to perform simultaneous measurements of dose profile and microdosimetric spectra with the Y1 proton passive scattering beamline of the Center of Proton Therapy, Institute Curie in Orsay, France. To qualify the performance of the set-up in clinical conditions of hadrontherapy, the dose, dose rate and energy loss pulse-height spectra in a diamond microdosimeter were recorded at multiple points along depth of a water-equivalent plastic phantom. The dose-mean lineal energy (y¯D) values were computed from experimental data and compared to silicon on insulator (SOI) microdosimeter literature results. In addition, the measured dose profile, pulse height spectra and y¯D values were benchmarked with a numerical simulation using TOPAS and Geant4 toolkits. These first clinical tests of a novel system confirm that diamond is a promising candidate for a tissue equivalent, radiation hard, high spatial resolution microdosimeter in beam quality assurance of proton therapy

scCVD diamond membrane based microdosimeter for hadron therapy

Hadron therapy is an innovative mode of radiation therapy for cancer treatment which enables tumour cells to be more effectively destroyed than conventional radiation therapy using photons. Based on single-crystal CVD, super-thin diamond membranes obtained using deep Ar/O plasma etching, a prototype of a solid-state microdosimeter for Linear Energy Transfer measurements was produced at the Diamond Sensors Laboratory of CEA-LIST. The response of the diamond membrane microdosimeter to single projectiles was investigated in ion micro-beams. This novel microdosimeter was tested in a 100 MeV therapeutic proton beam at Institut Curie and the experimental data compared to Monte Carlo simulation

scCVD diamond membrane based microdosimeter for hadron therapy

Hadron therapy is an innovative mode of radiation therapy for cancer treatment which enables tumour cells to be more effectively destroyed than conventional radiation therapy using photons. Based on single-crystal CVD, super-thin diamond membranes obtained using deep Ar/O plasma etching, a prototype of a solid-state microdosimeter for Linear Energy Transfer measurements was produced at the Diamond Sensors Laboratory of CEA-LIST. The response of the diamond membrane microdosimeter to single projectiles was investigated in ion micro-beams. This novel microdosimeter was tested in a 100 MeV therapeutic proton beam at Institut Curie and the experimental data compared to Monte Carlo simulation

scCVD diamond membrane based microdosimeter for hadron therapy

Hadron therapy is an innovative mode of radiation therapy for cancer treatment which enables tumour cells to be more effectively destroyed than conventional radiation therapy using photons. Based on single-crystal CVD, super-thin diamond membranes obtained using deep Ar/O plasma etching, a prototype of a solid-state microdosimeter for Linear Energy Transfer measurements was produced at the Diamond Sensors Laboratory of CEA-LIST. The response of the diamond membrane microdosimeter to single projectiles was investigated in ion micro-beams. This novel microdosimeter was tested in a 100 MeV therapeutic proton beam at Institut Curie and the experimental data compared to Monte Carlo simulation