Showing 1–7 of 7 results for author: Breton, V

Towards a quantum approach to cell membrane electrodynamics

Authors: J. Breton, V. Breton

Abstract: The ultimate active constituents of the living medium, membranes, ions and molecules, are at the level of the nanometer. Their interactions thus require a quantum processing. The characteristic Action A, linked to the "quantum objects" : ions, radicals, water molecule... of the living medium, has an average value of A ~= 14.10-34 J.s or A ~= 2 h . It is thus strictly impossible to formulate a re… ▽ More The ultimate active constituents of the living medium, membranes, ions and molecules, are at the level of the nanometer. Their interactions thus require a quantum processing. The characteristic Action A, linked to the "quantum objects" : ions, radicals, water molecule... of the living medium, has an average value of A ~= 14.10-34 J.s or A ~= 2 h . It is thus strictly impossible to formulate a realistic "classical " theory of membrane electrodynamics. The transfer of the sodium ion - among others - could be then ensured under the action of a Tunnel effect, (with Hartman?s mechanism) specific to the channel and the ion transferred. △ Less

Submitted 17 February, 2009; originally announced February 2009.

Comments: 7 pages

Towards grid-enabled telemedicine in Africa

Authors: F. Jacq, F. Bacin, N. Meda, D. Donnarieix, J. Salzemann, V. Vayssiere, N. Jacq, M. Renaud, F. Traore, G. Meda, R. Nikiema, V. Breton

Abstract: Telemedicine services are very relevant tools to train local physicians and to improve diagnosis by exchanging medical data. Telemedicine networks allow these exchanges but the set-up of multipoint dynamic telemedicine requires moving towards GRID technologies. A healthgrid is an environment where data of medical interest can be stored and is easily available between the different actors of heal… ▽ More Telemedicine services are very relevant tools to train local physicians and to improve diagnosis by exchanging medical data. Telemedicine networks allow these exchanges but the set-up of multipoint dynamic telemedicine requires moving towards GRID technologies. A healthgrid is an environment where data of medical interest can be stored and is easily available between the different actors of healthcare. Two telemedicine applications were developed to link physicians from Burkina Faso and France with the perspective of setting up a grid infrastructure between the participating medical sites. A web site to exchange diagnosis on diabetic retinopathy was developed in PHP and another application using web services was developed to exchange patient information between two databases. △ Less

Submitted 12 May, 2006; originally announced May 2006.

Comments: 7 pages, 1 figure, IST-Africa 2006 Conference, Pretoria, South Africa, to be published in the proceedings

Fully 3D Monte Carlo image reconstruction in SPECT using functional regions

Authors: Z. El Bitar, D. Lazaro, C. Coello, V. Breton, D. Hill, I. Buvat

Abstract: Image reconstruction in Single Photon Emission Computed Tomography (SPECT) is affected by physical effects such as photon attenuation, Compton scatter and detector response. These effects can be compensated for by modeling the corresponding spread of photons in 3D within the system matrix used for tomographic reconstruction. The fully 3D Monte Carlo (F3DMC) reconstruction technique consists in c… ▽ More Image reconstruction in Single Photon Emission Computed Tomography (SPECT) is affected by physical effects such as photon attenuation, Compton scatter and detector response. These effects can be compensated for by modeling the corresponding spread of photons in 3D within the system matrix used for tomographic reconstruction. The fully 3D Monte Carlo (F3DMC) reconstruction technique consists in calculating this system matrix using Monte Carlo simulations. The inverse problem of tomographic reconstruction is then solved using conventional iterative algorithms such as maximum likelihood expectation maximization (MLEM). Although F3DMC has already shown promising results, its use is currently limited by two major issues: huge size of the fully 3D system matrix and long computation time required for calculating a robust and accurate system matrix. To address these two issues, we propose to calculate the F3DMC system matrix using a spatial sampling matching the functional regions to be reconstructed. In this approach, different regions of interest can be reconstructed with different spatial sampling. For instance, a single value is reconstructed for a functional region assumed to contain uniform activity. To assess the value of this approach, Monte Carlo simulations have been performed using GATE. Results suggest that F3DMC reconstruction using functional regions improves quantitative accuracy compared to the F3DMC reconstruction method proposed so far. In addition, it considerably reduces disk space requirement and duration of the simulations needed to estimate the system matrix. The concept of functional regions might therefore make F3DMC reconstruction practically feasible. △ Less

Submitted 27 October, 2005; originally announced October 2005.

Comments: 6 pages, 3 figures, 3rd International Conference on maging Technologies in Biomedical Sciences : ITBS2005, Milos Island, Greece, 25-28 september 2005, submitted to NIMA

Monte Carlo tomographic reconstruction in SPECT impact of bootstrapping and number of generated events

Authors: Z. El Bitar, I. Buvat, V. Breton, D. Lazaro, D. Hill

Abstract: In Single Photon Emission Computed Tomography (SPECT), 3D images usually reconstructed by performing a set of bidimensional (2D) analytical or iterative reconstructions can also be reconstructed using an iterative reconstruction algorithm involving a 3D projector. Accurate Monte Carlo (MC) simulations modeling all the physical effects that affect the imaging process can be used to estimate this… ▽ More In Single Photon Emission Computed Tomography (SPECT), 3D images usually reconstructed by performing a set of bidimensional (2D) analytical or iterative reconstructions can also be reconstructed using an iterative reconstruction algorithm involving a 3D projector. Accurate Monte Carlo (MC) simulations modeling all the physical effects that affect the imaging process can be used to estimate this projector. However, the accuracy of the projector is affected by the stochastic nature of MC simulations. In this paper, we study the accuracy of the reconstructed images with respect to the number of simulated histories used to estimate the MC projector. Furthermore, we study the impact of applying the bootstrapping technique when estimating the projector △ Less

Submitted 25 July, 2005; originally announced July 2005.

Comments: 15 pages, 9 figures, 2 tables

Journal ref: Dans Open international conference on modeling and simulation (2005) 415-429

Effect of noise and modeling errors on the reliability of fully 3D Monte Carlo reconstruction in SPECT

Authors: D. Lazaro, Z. El Bitar, V. Breton, I. Buvat

Abstract: We recently demonstrated the value of reconstructing SPECT data with fully 3D Monte Carlo reconstruction (F3DMC), in terms of spatial resolution and quantification. This was shown on a small cubic phantom (64 projections 10 x 10) in some idealistic configurations. The goals of the present study were to assess the effect of noise and modeling errors on the reliability of F3DMC, to propose and eva… ▽ More We recently demonstrated the value of reconstructing SPECT data with fully 3D Monte Carlo reconstruction (F3DMC), in terms of spatial resolution and quantification. This was shown on a small cubic phantom (64 projections 10 x 10) in some idealistic configurations. The goals of the present study were to assess the effect of noise and modeling errors on the reliability of F3DMC, to propose and evaluate strategies for reducing the noise in the projector, and to demonstrate the feasibility of F3DMC for a dataset with realistic dimensions. A small cubic phantom and a realistic Jaszczak phantom dataset were considered. Projections and projectors for both phantoms were calculated using the Monte Carlo simulation code GATE. Projectors with different statistics were considered and two methods for reducing noise in the projector were investigated: one based on principal component analysis (PCA) and the other consisting in setting small probability values to zero. Energy and spatial shifts in projection sampling with respect to projector sampling were also introduced to test F3DMC in realistic conditions. Experiments with the cubic phantom showed the importance of using simulations with high statistics for calculating the projector, and the value of filtering the projector using a PCA approach. F3DMC was shown to be robust with respect to energy shift and small spatial sampling off-set between the projector and the projections. Images of the Jaszczak phantom were successfully reconstructed and also showed promising results in terms of spatial resolution recovery and quantitative accuracy in small structures. It is concluded that the promising results of F3DMC hold on realistic data sets △ Less

Submitted 17 December, 2004; originally announced December 2004.

Journal ref: Dans Proceedings (2004) 1-4 - Conference: IEEE Nuclear Science Symposium And Medical Imaging Conference (NSS / MIC) (2004-10-16 to 2004-10-22), Rome (it)

Validation of the GATE Monte Carlo simulation platform for modelling a CsI(Tl) scintillation camera dedicated to small animal imaging

Authors: D. Lazaro, I. Buvat, G. Loudos, D. Strul, G. Santin, N. Giokaris, D. Donnarieix, L. Maigne, V. Spanoudaki, S. Styliaris, S. Staelens, V. Breton

Abstract: Monte Carlo simulations are increasingly used in scintigraphic imaging to model imaging systems and to develop and assess tomographic reconstruction algorithms and correction methods for improved image quantitation. GATE (GEANT 4 Application for Tomographic Emission) is a new Monte Carlo simulation platform based on GEANT4 dedicated to nuclear imaging applications. This paper describes the GATE… ▽ More Monte Carlo simulations are increasingly used in scintigraphic imaging to model imaging systems and to develop and assess tomographic reconstruction algorithms and correction methods for improved image quantitation. GATE (GEANT 4 Application for Tomographic Emission) is a new Monte Carlo simulation platform based on GEANT4 dedicated to nuclear imaging applications. This paper describes the GATE simulation of a prototype of scintillation camera dedicated to small animal imaging and consisting of a CsI(Tl) crystal array coupled to a position sensitive photomultiplier tube. The relevance of GATE to model the camera prototype was assessed by comparing simulated 99mTc point spread functions, energy spectra, sensitivities, scatter fractions and image of a capillary phantom with the corresponding experimental measurements. Results showed an excellent agreement between simulated and experimental data: experimental spatial resolutions were predicted with an error less than 100 mu m. The difference between experimental and simulated system sensitivities for different source-to-collimator distances was within 2%. Simulated and experimental scatter fractions in a [98-182 keV] energy window differed by less than 2% for sources located in water. Simulated and experimental energy spectra agreed very well between 40 and 180 keV. These results demonstrate the ability and flexibility of GATE for simulating original detector designs. The main weakness of GATE concerns the long computation time it requires: this issue is currently under investigation by the GEANT4 and the GATE collaborations △ Less

Submitted 26 November, 2004; originally announced November 2004.

Journal ref: Physics in Medicine and Biology 49 (2004) 271-285

GATE : a simulation toolkit for PET and SPECT

Authors: S. Jan, G. Santin, D. Strul, S. Staelens, K. Assie, D. Autret, S. Avner, R. Barbier, M. Bardies, P. M. Bloomfield, D. Brasse, V. Breton, P. Bruyndonckx, I. Buvat, A. F. Chatziioannou, Y. Choi, Y. H. Chung, C. Comtat, D. Donnarieix, L. Ferrer, S. J. Glick, C. J. Groiselle, D. Guez, P. -F. Honore, S. Kerhoas-Cavata , et al. (28 additional authors not shown)

Abstract: Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols, and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted… ▽ More Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols, and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at the address http://www-lphe.epfl.ch/GATE/. △ Less

Submitted 24 August, 2004; originally announced August 2004.

Journal ref: Phys.Med.Biol.49:4543-4561,2004