arXiv subjects

Mathieu Dupont

Publications and source records attributed to Mathieu Dupont.

7 recordsLinked to original sources

arXiv2026

Prompt Gamma Timing in Carbon Therapy: First Experimental Results with the TIARA Detector

In the context of range monitoring for particle therapy, this study presents the first experimental results obtained with the TIARA detector using carbon-ion beams at the CNAO clinical center in Pavia, Italy. TIARA is based on the Prompt Gamma Timing (PGT) technique, which measures the time of flight (TOF) between incident ions and prompt gamma rays (PGs) emitted during nuclear interactions in the target. While the TIARA prototype has previously been validated with protons, carbons present a more challenging scenario due to their higher linear energy transfer, nuclear fragmentation products, and the continuous beam time structure of synchrotron accelerators. Experiments were performed by irradiating PMMA targets of different thicknesses with 200 MeV/u carbon beams. A coincidence time resolution of 279$\pm$35 ps FWHM was achieved, outperforming results previously obtained with protons at the same facility. A range accuracy of 4.74$\pm$0.36 mm at a 2$\sigma$ confidence level was measured at clinical intensity, when considering 5600 detected PGs, corresponding to the grouping of four irradiation spots of 2.4$\cdot$10$^6$ ions each. Overall, the results demonstrate that PGT-based range monitoring remains viable for carbon-ion beams, although increased background from secondary protons indicates that detector configuration adaptations are required.

physics.med-ph↗

arXiv2025

Validation of optical pathlength stability in a LISA test-bench demonstrator

The Laser Interferometer Space Antenna (LISA) observatory is a future L3 mission of the European Space Agency (ESA) to detect gravitational waves, set to launch in 2035. The detector constellation will conduct interferometry to picometer stability over an unprecedented arm length of 2.5 million km. In this paper, we present the development and testing results for the Zerodur interferometer (ZIFO), an optical demonstrator built to validate critical technology for the test setup of the interferometric core of LISA. Optical path length stability measurements on the ZIFO demonstrate successful reduction of bench noise to maintain the 10 pm/$\sqrt{\text{Hz}}$ specification across the 1 mHz to 1 Hz frequency band. We also identify and characterize dominant noise sources from phasemeters and correlations of beam tilt into the path length that were observed during the test campaign.

astro-ph.IM↗

arXiv2024

A fast plastic scintillator for low intensity proton beam monitoring

In the context of particle therapy monitoring, we are developing a gamma-ray detector to determine the ion range in vivo from the measurement of particle time-of-flight. For this application, a beam monitor capable to tag in time the incident ion with a time resolution below 235 ps FWHM (100 ps rms) is required to provide a start signal for the acquisition. We have therefore developed a dedicated detector based on a fast organic scintillator (EJ-204) of 25x25x1 mm3 coupled to four SiPM strips that allow measuring the particle incident position by scintillation light sharing. The prototype was characterised with single protons of energies between 63 and 225 MeV at the MEDICYC and ProteusONE facilities of the Antoine Lacassagne proton therapy centre in Nice. We obtained a time resolution of 120 ps FWHM at 63 MeV, and a spatial resolution of ~2 mm rms for single particles. Two identical detectors also allowed to measure the MEDICYC proton energy with 0.3% accuracy.

physics.ins-det↗

arXiv2023

A high sensitivity Cherenkov detector for Prompt Gamma Timing and Time Imaging

We recently proposed a new approach for the real-time monitoring of particle therapy treatments with the goal of achieving high sensitivities on the particle range measurement already at limited counting statistics. This method extends the Prompt Gamma (PG) timing technique to obtain the PG vertex distribution from the exclusive measurement of particle Time-Of-Flight (TOF). It was previously shown, through Monte Carlo simulation, that an original data reconstruction algorithm (Prompt Gamma Time Imaging) allows to combine the response of multiple detectors placed around the target. In this work we focus on the experimental feasibility of PGTI in Single Proton Regime (SPR) through the development of a multi-channel, Cherenkov-based PG detector with a targeted time resolution of 235 ps (FWHM): the TOF Imaging ARrAy (TIARA). The PG module that we developed is composed of a small PbF$_{2}$ crystal coupled to a silicon photoMultiplier to provide the time stamp of the PG. This prototype was tested with 63 MeV protons delivered from a cyclotron: a time resolution of 276 ps (FWHM) was obtained, resulting in a proton range sensitivity of 4 mm at 2$\sigma$ with the acquisition of only 600 PGs. A second prototype was also evaluated with 148 MeV protons delivered from a synchro-cyclotron obtaining a time resolution below 167 ps (FWHM) for the gamma detector. Moreover, using two identical PG modules, it was shown that a uniform sensitivity on the PG profiles would be achievable by combining the response of gamma detectors uniformly distributed around the target. This work provides the experimental proof-of-concept for the development of a high sensitivity detector that can be used to monitor particle therapy treatments and potentially act in real-time if the irradiation does not comply to treatment plan.

physics.med-ph↗

arXiv2022

Detailed simulation for the ClearMind prototype detection module and event reconstruction using artificial intelligence

The ClearMind project aims to develop the TOF-PET position sensitive detection module optimized for the time resolution, spatial resolution, and detection efficiency. For this, the ClearMind project uses a large (59 $\times$ 59 mm$^2$) monolithic PbWO$_4$ (PWO) scintillating crystal with a bialkali photo-electric layer deposited directly on the crystal. Scintillation and Cherenkov photons result together from the 511 keV gamma-ray interation into the PWO crystal. A micro-channel plate photomultiplier tube (MCP-PMT) encapsulating the PWO crystal amplifies photoelectrons generated at the photocathode, and the corresponding anode signals are collected through the transmission lines read out at both ends and digitized by a SAMPIC module. In this work, we present a realistic Geant4 simulation of the ClearMind prototype detector, including the propagation of the visible photons in the crystal, the modelling of a realistic response of the photocathode and of the PMT, and the propagation of the electrical signals over the transmission lines. The reconstruction of the gamma conversion in the detector volume is performed from the signals registered at both ends of the transmission lines. We compare the reconstruction precision of a statistical algorithm against machine learning algorithms developed using the TMVA package. We expect to reach a spatial resolution down to a few mm$^3$ (FWHM). Finally, we will discuss prospects for the ClearMind detector.

physics.ins-det↗

arXiv2020

A Time-Of-Flight-Based Reconstruction for Real-Time Prompt-Gamma Imaging in Protontherapy

We are currently conceiving, through (MC) simulation, a multi-channel gamma detector array (TIARA for Time-of-flight Imaging ARrAy) for the online monitoring of protontherapy treatments. By measuring the Time-Of-Flight (TOF) between a beam monitor placed upstream and the Prompt-Gamma (PG) detector, our goal is to reconstruct the PG vertex distribution to detect a possible deviation of proton beam delivery. In this paper, two non-iterative reconstruction strategies are proposed. The first is based on the resolution of an analytical formula describing the PG vertex distribution in 3D. Here, it was resolved under a one-dimensional approximation in order to measure a potential proton range shift along the beam direction. The second is based on the calculation of the Centre-Of-Gravity (COG) of the TIARA pixel detectors counts and also provides 3D information on a possible beam displacement. The PG vertex reconstruction was evaluated in two different scenarios. A coincidence time resolution of 100 ps (rms) can be attained in single proton regime (operating a reduction of the beam current) and using an external beam monitor to provide a start trigger for the TOF measurement. Under these conditions, MC simulations have shown that a millimetric proton range shift sensitivity can be achieved at 2$\sigma$ with 10$^{8}$ incident protons. This level of accuracy would allow to act in real-time if the treatment does not conform to treatment plan. A worst case scenario of a 1 ns (rms) TOF resolution was also considered to demonstrate that a degraded timing information can be compensated by increasing the acquisition statistics: in this case, a 2 mm range shift would be detectable at 2$\sigma$ with 10$^{9}$ incident protons. The COG method has shown excellent capabilities of detecting lateral beam displacements: a 2 mm sensitivity was found at 2$\sigma$ with 10$^{8}$ incident protons.

physics.med-ph↗

arXiv2008

Abelian categories in dimension 2

The goal of this thesis is to define a 2-dimensional version of abelian categories, where symmetric 2-groups play the role that abelian groups played in 1-dimensional algebra. Abelian and 2-abelian groupoid enriched categories are defined and it is proved that homology can be developed in them, including the existence of a long exact sequence of homology corresponding to an extension of chain complexes. This generalises known results for symmetric 2-groups. The examples include, in addition to symmetric 2-groups, the 2-modules on a 2-ring, which form a 2-abelian groupoid enriched category. Moreover, internal groupoids, functors and natural transformations in an abelian category C (in particular, Baez-Crans 2-vector spaces) form a 2-abelian groupoid enriched category if and only if the axiom of choice holds in C.

math.CT↗