M Bajard

University of Lyon, Lyons, Rhône-Alpes, France

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Publications (15)11.88 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Prompt-gamma emission detection is a promising technique for hadrontherapy monitoring purposes. In this regard, obtaining prompt-gamma yields that can be used to develop monitoring systems based on this principle is of utmost importance since any camera design must cope with the available signal. Herein, a comprehensive study of the data from ten single-slit experiments is presented, five consisting in the irradiation of either PMMA or water targets with lower and higher energy carbon ions, and another five experiments using PMMA targets and proton beams. Analysis techniques such as background subtraction methods, geometrical normalization, and systematic uncertainty estimation were applied to the data in order to obtain absolute prompt-gamma yields in units of prompt-gamma counts per incident ion, unit of field of view, and unit of solid angle. At the entrance of a PMMA target, where the contribution of secondary nuclear reactions is negligible, prompt-gamma counts per incident ion, per millimetre and per steradian equal to (124 ± 0.7stat ± 30sys) × 10(-6) for 95 MeV u(-1) carbon ions, (79 ± 2stat ± 23sys) × 10(-6) for 310 MeV u(-1) carbon ions, and (16 ± 0.07stat ± 1sys) × 10(-6) for 160 MeV protons were found for prompt gammas with energies higher than 1 MeV. This shows a factor 5 between the yields of two different ions species with the same range in water (160 MeV protons and 310 MeV u(-1) carbon ions). The target composition was also found to influence the prompt-gamma yield since, for 300/310 MeV u(-1) carbon ions, a 42% greater yield ((112 ± 1stat ± 22sys) × 10(-6) counts ion(-1) mm(-1) sr(-1)) was obtained with a water target compared to a PMMA one.
    Physics in Medicine and Biology 12/2014; 60(2):565-594. · 2.92 Impact Factor
  • 50th International PTCOG meeting (Particle Therapy Co-Operative Group); 05/2011
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    ABSTRACT: Monte Carlo simulations based on the Geant4 toolkit (version 9.1) were performed to study the emission of secondary prompt-gamma rays produced by nuclear reactions during carbon ion-beam therapy. These simulations were performed along with an experimental program and instrumentation developments which aim at designing a prompt-gamma ray device for real-time control of hadrontherapy. The objective of the present study is twofold: firstly, to present the features of the prompt-gamma radiation in the case of carbon ion irradiation; secondly, to simulate the experimental setup and to compare measured and simulated counting rates corresponding to four different experiments. For each experiment, we found that simulations overestimate prompt-gamma ray detection yields by a factor of 12. Uncertainties in fragmentation cross sections and binary cascade model cannot explain such discrepancies. The so-called “photon evaporation” model is therefore questionable and its modification is currently in progress.
    IEEE Transactions on Nuclear Science 11/2010; · 1.46 Impact Factor
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    ABSTRACT: The increased effectiveness of highly conformal ion beam therapy requires a higher precision in the dose monitoring and location than in conventional radiation therapy. To monitor in real time the longitudinal position of the Bragg peak we proposed a novel non invasive technique that exploits the detection of prompt gamma-rays issued from nuclear fragmentation. In our first experiment with a 73 MeV/u 13C6+ ion beam we showed that i) the ion depth-dose profile is correlated with the prompt-gamma-ray profile and that ii) the use of the time-of-flight (TOF) technique allows to use a compact device which makes it possible to increase the detection solid angle by 2 or 3 orders of magnitude. We could therefore obtain counting rates high enough for real-time control of the Bragg peak position as compared to the passive neutron-shielded camera previously developed by Min et al. We have recently carried out two series of experiments at the GANIL and GSI facilities with 95 MeV/u and 310 MeV/u 12C6+ ion beams, respectively. The carbon beam was stopped in a PMMA or water target. In both experiments, our collimated detectors were placed at 90 degrees from the beam direction and aimed at the target. The target was placed on a translating table, moving along the beam axis, to allow a full scan of the beam profile inside the target. To discriminate the prompt photons from the background radiation, mainly due or induced by neutrons, we used the TOF and the Pulse Shape Discrimination (PSD) techniques. We showed that TOF could make real-time treatment monitoring with prompt gamma-rays feasible, since it avoids the use of bulky neutron shielding. On the contrary no correlation between the neutron production and the ion path was found. The proposed technique remains valid with patient-like target volumes and the gamma profile is still correlated with the ion depth of penetration. We present our recent developments of a beam monitor, based on scintillating fibres read out by a flat-panel multi-channel photomultiplier, to allow precise beam tagging in time and position in the plane transverse to the beam. A prototype of such a beam hodoscope with 1 mm square scintillating fibres was tested at GANIL, providing encouraging performances concerning the time resolution (rms 350 ps), and sufficient radiation hardness to make their use possible in routine clinical conditions.
    07/2010;
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    ABSTRACT: Hadrontherapy treatments require a very high precision on the location of the dose in order to keep the benefits of the precise ions' ballistic. The largest uncertainty on physical dose is due to ion fragmentation. Up to now, the simulation codes are not able to reproduce the fragmentation process with the required precision. The constraints on nuclear models and fragmentation cross sections between 30 and 100MeV/u are not sufficient. We have performed an experiment on May 2008 at GANIL,France with a 95 MeV/u 12C beam. The goals were the measurement of the fluence, energy and angular distributions of the fragments coming from the nuclear reaction between 12C and waterlike PMMA targets of different thicknesses : from 0.5 to 4 cm. At 95MeV/u, the 12C Bragg Peak depth in PMMA is 2 cm. Production rates, from proton to carbons, have been obtained at 10 different angles for the six different PMMA thicknesses. The setup also included DEMON detectors to measure the neutrons at four different angles (15, 25, 45 and 70 degrees). Comparisons between our data and Geant4 simulations have been achieved in order to evaluate the accuracy of the models (eg. G4BinaryLightIonReaction, G4BinaryCascade) included in GEANT4 for hadrontherapy purposes (light ion on light target; energy range: 80-400MeV/u). While we are in good agreement with the angular distribution of proton, beryum and bore ions, these comparisons show some discrepancies for helium lithium and carbon ions. Further studies are underway to find a model in good agreement with all our data. We also have another experiment accepted on thin targets at GANIL (C-C, C-H, C-O, C-Ca from 40 to 95 MeV/u). These double differential cross sections of charged fragments and neutrons are necessary to improve the models and reach the precision required for a reference simulation code for hadrontherapy. These activities will experience a boost with the arrival of a new resource center in hadrontherapy, Archade in Caen, France.
    06/2010;
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    ABSTRACT: For real-time monitoring of the longitudinal position of the Bragg-peak during an ion therapy treatment, a novel non-invasive technique has been recently proposed that exploits the detection of prompt gamma-rays issued from nuclear fragmentation. Two series of experiments have been performed at the GANIL and GSI facilities with 95 and 305 MeV/u (12)C(6+) ion beams stopped in PMMA and water phantoms. In both experiments, a clear correlation was obtained between the carbon ion range and the prompt photon profile. Additionally, an extensive study has been performed to investigate whether a prompt neutron component may be correlated with the carbon ion range. No such correlation was found. The present paper demonstrates that a collimated set-up can be used to detect single photons by means of time-of-flight measurements, at those high energies typical for ion therapy. Moreover, the applicability of the technique both at cyclotron and at synchrotron facilities is shown. It is concluded that the detected photon count rates provide sufficiently high statistics to allow real-time control of the longitudinal position of the Bragg-peak under clinical conditions.
    Biophysik 03/2010; 49(3):337-43. · 1.70 Impact Factor
  • First International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA); 06/2009
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    ABSTRACT: A key point in the quality control of ion therapy is real-time monitoring and imaging of the dose delivered to the patient. Among the possible signals that can be used to make such a monitoring, prompt gamma-rays issued from nuclear fragmentation are possible candidates, provided the correlation between the emission profile and the primary beam range can be established. By means of simultaneous energy and time-of-flight discrimination, we could measure the longitudinal profile of the prompt gamma-rays emitted by 73 MeV/u carbon ions stopping inside a PMMA target. This technique allowed us to minimize the shielding against neutrons and scattered gamma rays, and to find a good correlation between the prompt-gamma profile and the ion range. This profile was studied as a function of the observation angle. By extrapolating our results to higher energies and realistic detection efficiencies, we showed that prompt gamma-ray measurements make it feasible to control in real time the longitudinal dose during ion therapy treatments.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 03/2009; · 1.19 Impact Factor
  • International Workshop on Hadron Beam Therapy of cancer, Erice, Italie, 24 avril - 1er mai 2009; 01/2009
  • International Conference - Heavy Ions in Therapy and Space Symposium 2009, 12th Workshop on Ion Beams in Biology and Medicine (IBIBAM), Cologne, 6-10 juillet 2009; 01/2009
  • 01/2009;
  • IEEE Nuclear Science Symposium, Medical Imaging Conference; 10/2008
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    ABSTRACT: By means of a time-of-flight technique, we measured the longitudinal profile of prompt $\gamma$-rays emitted by 73 MeV/u $^{13}$C ions irradiating a PMMA target. This technique allowed us to minimize the shielding against neutrons and scattered $\gamma$-rays, and to correlate prompt gamma emission to the ion path. This correlation, together with a high counting rate, paves the way toward real-time monitoring of the longitudinal dose profile during ion therapy treatments. Moreover, the time correlation between the prompt gamma detection and the transverse position of the incident ions measured by a beam monitor can provide real-time 3D control of the irradiation.
    Applied Physics Letters 10/2008; · 3.52 Impact Factor
  • Cancer/Radiothérapie 11/2007; 11(6):397-398. · 1.11 Impact Factor
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    M Bajard
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    ABSTRACT: The ETOILE project is the French program for carbon ion beams in cancer treatment. It is now in the final phase. However its development is not only aiming at the building of a medical facility, around the project a broad set of medical and scientific programs have been initiated. The project has been supported by the University of Lyon and extended to the Rhône-Alpes Region and then gained a national visibility with governmental recognition. Many studies have been financed by ETOILE: in beam PET with new solutions, organ motion modelization, tumor cell radioresistance, medico-economical simulation and epidemiological prevision. The facility will be able to produce carbon ion beams and protons. Three treatment rooms are planned two with horizontal beams and one with an isocentric gantry. The facility will be build in Lyon through a process using as much as possible well established technology with the other facilities in Europe. The cost will be around 105 M€ afforded by loans and subventions. The subventions are funded from the Rhône-Alpes Region, the city of Lyon and the ministries of Health and Research. The running cost of the centre, for one thousand patients per year, is estimated to be 21 M€.