Didier Vray - Academia.edu (original) (raw)

Papers by Didier Vray

Biomedical Imaging: From …

We present a simple, robust and computationally efficient method for the semi-automatic segmentat... more We present a simple, robust and computationally efficient method for the semi-automatic segmentation of the prostate in TRUS (Transrectal Ultrasound) image. The method relies on a variational formulation based on a deformable superellipse and a region energy based on the assumption of a Rayleigh distribution. Instead of using the classical level-set approach, we directly insert the implicit representation of a deformable super-ellipse into the energy to minimize. This yields a super-ellipse evolution able to accurately segment prostate and surrounding tissues while handling boundary gaps on the contour.

Biomedical Image Processing and Biomedical Visualization, 1993

ABSTRACT

Biomedical Optics Express, 2015

This paper proposes a multigrid inversion framework for quantitative photoacoustic tomography rec... more This paper proposes a multigrid inversion framework for quantitative photoacoustic tomography reconstruction. The forward model of optical fluence distribution and the inverse problem are solved at multiple resolutions. A fixed-point iteration scheme is formulated for each resolution and used as a cost function. The simulated and experimental results for quantitative photoacoustic tomography reconstruction show that the proposed multigrid inversion can dramatically reduce the required number of iterations for the optimization process without loss of reliability in the results.

Le Journal de Physique Colloques, 1990

Le concept de fréquence instantanée est utilisé pour décrire l'effet Doppler produit par une cibl... more Le concept de fréquence instantanée est utilisé pour décrire l'effet Doppler produit par une cible en mouvement rectiligne uniforme, le transducteur émetteur-récepteur n'étant pas situé sur la trajectoire. La vitesse radiale dépendant du temps, la fréquence Doppler, fréquence de l'enveloppe complexe associée au signal reçu, dépend également du temps. La prise en compte de l'amplitude des signaux permet alors de simuler la situation expérimentale.

Optical Biopsy IX, 2011

ABSTRACT The protocol for prostate cancer diagnosis, currently based on ultrasound guided biopsy,... more ABSTRACT The protocol for prostate cancer diagnosis, currently based on ultrasound guided biopsy, is limited by a lack of relevance. To improve this protocol, a new approach was proposed combining optical and ultrasound measurements to guide biopsy specifically to the tumors. Adding an optical measurement modality into an already existing ultrasound probe is challenging as the overall size of the system should not exceed a given dimension so as to fit the operative environment. Moreover, examination should not take more than 15 min to avoid any complication. A combined ultrasound and optical endorectal probe was designed to comply with the constraints of the sterilization protocols, the examination duration and required compactness. Therefore a totally innovative pulsed laser source has been designed to meet compactness requirements while providing accurate time-resolved measurements. A dedicated multi-channel photon counting system was optimized to decrease the examination duration. A fast reconstruction method based on the analysis of the intensity and time of flight of the detected photons has been associated to provide 3D localization of fluorescent dots almost immediately after acquisition. The bi-modal probe was capable of withstanding the sterilization procedures. The performance of the compact laser source has been shown at the same level as that of a standard laboratory Titane:Sapphire laser. The dedicated photon counting solution was capable of acquiring optical data in less than one minute. To evaluate the overall performance of the system in dealing with a realistic background signal, measurements and reconstructions were conducted on prostate mimicking phantom and in vivo.

2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263), 2001

A major complication of atherosclerosis remains plaque ruptures which consequences can be acute t... more A major complication of atherosclerosis remains plaque ruptures which consequences can be acute thrombosis, myocardial infarct and sudden ischaemic death. Medium elastic properties are deeply involved in rupture mechanisms and can be investigated by Elastography, which estimates from pairs of RF ultrasound signals, the strain distribution occurring within a medium, in response to a stress. In this paper, elastograms obtained with an original 2-layer vessel mimicking cryogel phantom and a fresh excised human carotid artery are presented. The experimental setup consists mainly in a CVIS ultrasound scanner with a 30 MHz mechanical rotating single element, an oscilloscope Lecroy 9374L and a self-made pressuring system modifying the static lumen pressure by varying the fluid volume. RF data were digitised at a sampling frequency of 500 MHz, stored on disc and processed off-line with a method we developed, based on the principle that tissue deformation induces within RF signals, variations comparable to local compression factors. This method has been proved to be accurate for strains up to 7% and very adapted for investigating highly heterogeneous tissues like atherosclerotic arteries. Results have shown the method ability to separate regions with different mechanical properties, whereas the acoustical features are similar. Moreover the phantom elastogram exhibits between the two layers a strain ratio that matches perfectly reported abacus on the cryogel stiffness. In parallel arterial elastograms by presenting estimated strains in a wider range [0%-3.5%] than previous reported results, improve the discrimination between healthy and diseased regions

1999 IEEE Ultrasonics Symposium. Proceedings. International Symposium (Cat. No.99CH37027), 1999

A model has been developed for correcting geometric artifacts observed in intravascular ultrasoun... more A model has been developed for correcting geometric artifacts observed in intravascular ultrasound imaging during coronary artery stent implantation. Geometric artifacts occur when the position of the transducer inside the stent is off-centered and inclined. In coronary applications, the position of the catheter changes a lot due to the curved nature of the arteries. This gives images that do not

1998 IEEE Ultrasonics Symposium. Proceedings (Cat. No. 98CH36102), 1998

IEEE Oceanic Engineering Society. OCEANS'98. Conference Proceedings (Cat. No.98CH36259), 1998

A FOURIER-BASED MOTION ESTIMATION APPROACH FOR WIDE BAND SYNTHETICAPERTURE SONAR ... Furthermore,... more A FOURIER-BASED MOTION ESTIMATION APPROACH FOR WIDE BAND SYNTHETICAPERTURE SONAR ... Furthermore, the azimuth resolution can be improved thanks to the synthetic aperture technique, which uses the movement of the towfish carrying the radiating sonar [I ...

1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118), 1997

Synthetic aperture focusing technique enables high resolution ultrasonic imaging. Nevertheless, t... more Synthetic aperture focusing technique enables high resolution ultrasonic imaging. Nevertheless, the synthetic antenna must be correctly spatially sampled in order to satisfy the Shannon constraint, which limits the mapping rate. We show that this constraint can be overcome without resultant aliasing, thanks to the digital spotlighting technique. The mapping rate is then significantly improved

1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118), 1997

Intravascular ultrasound imaging using a rotating transducer produces images which includes the P... more Intravascular ultrasound imaging using a rotating transducer produces images which includes the Point Spread Function of the imaging system. It results a lack of spatial resolution for the images. After the modelization of the image formation, the authors take into account the characteristics of the PSF in order to suggest an original Synthetic Aperture Focusing Technique (SAFT). The authors propose

OCEANS 96 MTS/IEEE Conference Proceedings. The Coastal Ocean - Prospects for the 21st Century, 1996

Synthetic aperture imaging can be achieved either in the time domain or in the frequency domain. ... more Synthetic aperture imaging can be achieved either in the time domain or in the frequency domain. These two approaches are compared in terms of spatial resolution, mathematical formalism and implementation. The application of Fourier-based imaging to synthetic aperture sonar is suggested. The whole processing is then performed in the frequency domain. The authors show that target detection is improved with

Medical Imaging 2004: Ultrasonic Imaging and Signal Processing, 2004

This work presents a new approach to lateral strain estimation in the field of tissue elasticity ... more This work presents a new approach to lateral strain estimation in the field of tissue elasticity imaging with ultrasound. A particular beamforming is used to produce a point spread function (PSF) with lateral oscillations. Lateral RF signals can then be considered as the juxtaposition of RF samples coming from the same depth. This enables to estimate the lateral strain with

Medical Imaging 2005: Ultrasonic Imaging and Signal Processing, 2005

Strain imaging is useful for visualizing information related to tissue stiffness. However, strain... more Strain imaging is useful for visualizing information related to tissue stiffness. However, strain is a parameter that depends on the boundary conditions, tissue connectivity and geometry. As a result, tissue hardness cannot be quantitatively evaluated from the strain distribution. Therefore, reconstruction of the elastic modulus (Young's Modulus) distribution has been investigated for quantitative evaluation of tissue hardness. A method has

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2007

Emerging medical imaging techniques usually provide quantitative diagnostic parameters. Since the... more Emerging medical imaging techniques usually provide quantitative diagnostic parameters. Since the description of a method for quantitative imaging of strain and elastic modulus distributions in soft tissues by Ophir et al. in 1991, research in elastography is progressing and experimental in vitro validation of new displacement estimators appears crucial for clinical applications. Materials mimicking biological tissues appear very useful to reach this goal. Nevertheless, correct validation necessitates knowledge of mechanical properties of the investigated material, which are often difficult to obtain. This study describes a simple method for mechanical characterization of gels used in elastography. We demonstrated the possibility to assess elasticity modulus with a reasonable reproducibility using simple tools and methods. For validation, the described method was further tested with 5 samples of Polyvinyl alcohol (PVA) cryogel having different values of elasticity. Young's modul...

Revue de Physique Appliquée, 1985

ABSTRACT

2007 IEEE Ultrasonics Symposium Proceedings, 2007

... Ultrasound Images A.MARION1, D.VRAY1 1CREATIS-LRMN, CNRS, UMR5220, INSERM, U630, INSA-LYON, U... more ... Ultrasound Images A.MARION1, D.VRAY1 1CREATIS-LRMN, CNRS, UMR5220, INSERM, U630, INSA-LYON, UCBL, F-69621 Villeurbanne, France adrien.marion@creatis.insa-lyon.fr didier.vray@creatis.insa-lyon.fr A.NEEDLES2 2VISUALSONICS INC., ... F F V F F V (4) Fx Ft Ft ...

Proceedings of OCEANS'94, 1994

This work deals with the response of underwater bottom insonified with wideband ultrasonic signal... more This work deals with the response of underwater bottom insonified with wideband ultrasonic signals. The aim of the study is to investigate the feasibility to recognize the nature of sediment layer using a wideband sonar system. The processing of signals must take into account the wide frequency band of the backscattered echoes and so includes spectral analysis and time-frequency analysis.

IEEE 1988 Ultrasonics Symposium Proceedings., 1988

An effort is made to determine, at each instant, the direction and the magnitude of the velocity ... more An effort is made to determine, at each instant, the direction and the magnitude of the velocity of a flow-carried target, provided this target moves within the field monitored by the measuring device. Four transducers (one transmitter and three receivers) are used because the Doppler phenomenon is three-dimensional in the present case. The interaction between the incident ultrasonic wave and

IEEE 1992 Ultrasonics Symposium Proceedings, 1992