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Publications (6)2.86 Total impact

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    ABSTRACT: In biomedical ultrasound imaging, many studies show the advantages of harmonics to obtain a better quality of image; this is particularly true in echography and diffraction tomography. Recent work confirms that lateral resolution can be improved by the use of the harmonics generated by a nonlinear distortion in the medium. In this study, the enhancement made by the use of the second harmonic in ultrasound reflection tomography is shown. A focused transducer containing both concentric 2.5 and 5 MHz elements composes the experimental device. They are, respectively, the transmitter/receiver of the fundamental field and the receiver of the second harmonic field. The tests are carried out with PVC tubes. The first object is a single tube whereas the second one is an asymmetrical structure made up of two tubes. The image reconstruction is made from the measurements of the fundamental and second harmonics of the reflected fields using the back-projection method. This technique of relying on higher harmonics seems to provide a better resolution of tomographic images.
    Measurement Science and Technology 10/2003; 15(1):21. · 1.44 Impact Factor
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    ABSTRACT: This article presents a theoretical and experimental study on the use of second harmonic in tomographic images reconstruction. A theoretical study based on KZK equation shows the different properties of the second harmonic ultrasonic beam. An algorithm using finite differences method allows to simulate the acoustic field taking into account diffraction, non-linearity and absorption phenomena. The experimental device uses a piezoelectric disc of 2 cm diameter emitting to 3 MHz. For the reception, a wideband hydrophone permit to measure the transmitted field. For tomographic images reconstruction, one measures the diffracted field by a cylindrical object of 2 cm diameter. An image reconstruction program based on Fourier diffraction theorem gives slice images of the examined object
    ITBM-RBM. 04/2002;
  • ITBM-RBM 01/2002; 23(2).
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    ABSTRACT: En vue d'augmenter la résolution des images, cette étude présente l'intérêt d'utiliser les harmoniques générés par distorsion ultrasonore en tomographie par diffraction. La reconstruction des images est bas ée sur la méthode analytique de Fourier. Le dispositif expérimental utilise un disque piézo-électrique de 2 cm de diamètre émettant à 3 MHz. Un hydrophone large bande à la réception permet de mesurer le champ transmis. Une comparaison entre l'image du fondamental et les images des trois harmoniques successifs montre que la qualit é de l'image augmente avec l'ordre de l'harmonique utilisé. Cette amélioration est due à la bonne directivité du faisceau et à l'atténuation des lobes secondaires.
    Acta Acustica united with Acustica 02/2001; 87(2):170-175. · 0.71 Impact Factor
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    ABSTRACT: The non-linear propagation of ultrasound in medical imaging has recently been exploited to improve image resolution and remove near field artifacts generated by overlying tissue structures. The images are formed using the second harmonic energy generated by nonlinear propagation. Second harmonic beams have narrower beam width and lower side lobes than the fundamental. The second harmonic draws energy from the fundamental continuously along the propagation path. These characteristics contribute to improve the quality of medical ultrasound images. In this paper, our objective is to show that the choice source aperture has significant consequences on the quality of the field transmitted in terms of directivity. We also studied the field generated by three apertures sources, in a nonlinear medium. A theoretical approach, based on the Khokhlov-Zabolotskaya-Kuznetsov (KZK) parabolic approximation is used in order to consider the diffraction effects related to the use of a focusing real source. The fundamental ultrasonic fields and the second harmonic are compared at three distances from the source. Width and side lobes were used when recording three distributions of the beam form.
    Engineering in Medicine and Biology Society, 2001. Proceedings of the 23rd Annual International Conference of the IEEE; 02/2001
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    ABSTRACT: In order to increase images resolution, this study present the use of the harmonics wave generated by ultrasonic distortion, in diffraction tomography imaging. The image reconstruction is based on Fourier diffraction theorem. The experimental setup is based on a 3 MHz circular transducer with 2 cm of diameter. Transmitted field is detected using a wide bandwith hydrophone. A comparison between the image of the fundamental wave with the images of the three successive harmonics waves shows that the quality of the image increases with the harmonic order. This improvement is due to beam directivity and secondary lobes attenuation. French En vue d'augmenter la résolution des images, cette étude présente l'intérêt d'utiliser les harmoniques générés par distorsion ultrasonore en tomographie par diffraction. La reconstruction des images est bas ée sur la méthode analytique de Fourier. Le dispositif expérimental utilise un disque piézo-électrique de 2 cm de diamètre émettant à 3 MHz. Un hydrophone large bande à la réception permet de mesurer le champ transmis. Une comparaison entre l'image du fondamental et les images des trois harmoniques successifs montre que la qualit é de l'image augmente avec l'ordre de l'harmonique utilisé. Cette amélioration est due à la bonne directivité du faisceau et à l'atténuation des lobes secondaires.
    Acta Acustica united with Acustica 01/2001; 87(2). · 0.71 Impact Factor