Ultrasound Image Post-Processing: application to segmentation

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Ultrasound Contrast Agents

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Frequency domain-based strain estimation and high frame-rate imaging for quasi-static elastography

International audienceIn freehand elastography, quasi-static tissue compression is applied through the ultrasound probe, and the corresponding axial strain is estimated by calculating the time shift between consecutive echo signals. This calculation typically suffers from a poor signal-to-noise ratio or from the decorrelation between consecutive echoes resulting from an erroneous axial motion impressed by the operator. This paper shows that the quality of elastograms can be improved through the integration of two distinct techniques in the strain estimation procedure. The first technique evaluates the displacement of the tissue by analyzing the phases of the echo signal spectra acquired during compression. The second technique increases the displacement estimation robustness by averaging multiple displacement estimations in a high-frame-rate imaging system, while maintaining the typical elastogram frame-rate. The experimental results, obtained with the Ultrasound Advanced Open Platform (ULA-OP) and a cyst phantom, demonstrate that each of the proposed methods can independently improve the quality of elastograms, and that further improvements are possible through their combination

A Nonlinear Ultrasound Propagation Simulator Using the Slowly Varying Envelope Approximation

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Acquire real-time RF digital ultrasound data from a commercial scanner

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Description d'une méthode expérimentale d'analyse « vectorielle » de la pression rayonnée par une bulle

Des bulles stationnaires, excitées à leur fréquence de résonance par une onde ultrasonore, rayonnent une onde fortement non linéaire. On décrit ici une méthode expérimentale basée sur le principe de la détection synchrone qui permet la mesure simultanée de l'amplitude et de la phase de la pression rayonnée par la bulle. Les résultats présentés constituent des vérifications préliminaires comme : la proportionnalité de l'amplitude du premier harmonique de la pression rayonnée à l'amplitude de la pression excitatrice; la proportionnalité de l'amplitude du second harmonique de la pression rayonnée au carré de la pression excitatrice ; l'évolution de l'amplitude de ces deux premiers harmoniques en fonction de la distance entre la bulle et le récepteur. Les bulles étudiées ont un diamètre de l'ordre de 130 μm, les fréquences utilisées sont donc de l'ordre de 25 kHz

Automatic Needle Detection and Tracking in 3D Ultrasound Using an ROI-Based RANSAC and Kalman Method

International audienceThis article proposes a robust technique for needle detection and tracking using three-dimensional ultrasound (3D US). It is difficult for radiologists to detect and follow the position of micro tools, such as biopsy needles, that are inserted in human tissues under 3D US guidance. To overcome this difficulty, we propose a method that automatically reduces the processed volume to a limited region of interest (ROI), increasing at the same time the calculation speed and the robustness of the proposed technique. First, a line filter method that enhances the contrast of the needle against the background is used to facilitate the initialization of ROI using the tubularness information of the complete US volume. Then, the random sample consensus (RANSAC) and Kalman filter (RK) algorithm is used in the ROI to detect and track the precise position of the needle. A series of numerical inhomogeneous phantoms with a needle simulated from real 3D US volumes are used to evaluate our method. The results show that the proposed method is much more robust than the RANSAC algorithm when detecting the needle, regardless of whether or not the insertion axis corresponds to an acquisition plane in the 3D US volume. The possibility of failure is also discussed in this article

Evaluation de l'agar, matériau solide présentant des caractéristiques acoustiques équivalentes à celles de l'eau

Le but de cette étude est de déterminer les caractéristiques acoustiques de l'agar, un matériau acoustiquement proche de l'eau. L'avantage de l'agar est que c'est un matériau solide, ce qui élargit son domaine d'application. Avec de telles propriétés, l'agar peut être utilisé comme conteneur de solutions liquides lors de leur caractérisation. De plus, son utilisation comme milieu de couplage ne nécessite pas un contact physique entre la cible et l'émetteur. Son utilisation peut s'étendre également au domaine médical (échographie) où il peut servir comme fantôme pour des évaluations ultrasonores des tissus.The aim of our work is to determine the acoustic caracteristics of agar, a material acoustically equivalent to water. The advantage of the use of agar is that it presents properties very neighbouring to those of water, and it's a solid material. Such properties make its areas very diversified and include medicine domain (echography) where it's used as a phantom. It's also used as an insulator to eliminate echos which may be important with respect to informationel echos. So, it's too necessary to know his acoustic behaviour by determining the attenuation coefficient, the speed of sound and the acoustic impedance