Réunion

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Signal et Imagerie Acoustique

Date : 21-06-2022
Lieu : CNRS délégation de Villejuif

Thèmes scientifiques :
  • A - Méthodes et modèles en traitement de signal

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Inscriptions

16 personnes membres du GdR ISIS, et 10 personnes non membres du GdR, sont inscrits à cette réunion.

Capacité de la salle : 94 personnes.

Annonce

L'acquisition et l'exploitation de données acoustiques est au coeur d'applications variées : échographie médicale, évaluation et contrôle non destructifs de matériaux, sismique, océanographie, ...

Si les modalités de mesure et les pratiques d'analyse associées diffèrent sensiblement d'une communauté scientifique à l'autre, elles partagent également de nombreuses similitudes. Outre la nature même des données, les problématiques liées à la formation d'image, au débruitage et aux problèmes inverses tiennent une place importante dans ces domaines. L'émergence de dispositifs de mesure toujours plus puissants s'accompagne également d'évolutions nécessaires dans les méthodes de traitement. L'acquisition et l'analyse de données multi-capteurs et multi-fréquences, l'imagerie 3D et les contraintes d'imagerie en temps réel, l'émergence de méthodes d'apprentissage automatique en sont quelques exemples.

L'objectif de la journée Signal et Imagerie Acoustique est de rassembler les acteurs de l'imagerie acoustique appliquée dans ces domaines afin d'améliorer leur fertilisation croisée.

La journée comportera 2 présentations invitées ainsi que des communications pour lesquelles un appel à contribution est lancé. Les personnes interessées peuvent envoyer un résumé (1/2 page maximum) aux organisateurs. Date limite 15 mai.

Organisateurs

  • Sébastien Bourguignon (LS2N, Centrale Nantes), sebastien.bourguignon@ec-nantes.fr
  • Barbara Nicolas (CREATIS, CNRS), barbara.nicolas@creatis.insa-lyon.fr

Programme

A venir.

Résumés des contributions

Présentations invitées

Denis Kouamé, Université Toulouse III Paul Sabatier, IRIT, Toulouse

Inverse problems in medical ultrasound imaging: Recent Advances and Open challenges

In the recent years, many important advances have been made in medical ultrasound imaging devices, especially in the optimization of high frame image acquisition and reconstruction systems.

However, medical ultrasound, unlike other medical imaging modalities, has not fully benefited from the most recent advances in image processing and analysis in general. This is mainly due to the intrinsic nature of ultrasound images, that limits the immediate translation of most recent developments.

Nevertheless, this is currently changing. There is nowadays a strong interest in medical ultrasound image processing for restoration, sparse representations, or machine learning.

This talk will focus on Inverse problems in ultrasound imaging through recent advances and open challenges.

Bruce Drinkwater, University of Bristol, Bristol, UK

What information can ultrasonic arrays extract from engineering structures?

Ultrasonics is one of the most widely used non-destructive testing methods due to its ability to receive signals from defects hidden deep within engineering structures. This talk reviews the recent dramatic increase in the use of ultrasonic arrays, capable of forming accurate and intuitive images of the interior of the structure. The high resolution now possible in array images means that smaller defects can be detected, and their shape extracted. The ever-increasing power of computers means that the full matrix capture dataset can be rapidly captured and analysed to extract the maximum available information. Of particular importance is the defect scattering behaviour, as this is the fingerprint that encodes the properties of the defect. As an ultrasonic array illuminates each defect from a range of angles it thereby examines a small portion of the defect's scattering matrix. These scattered signals are useful as they encode information about the characteristics of the defect. The question then is, given some array reflectivity measurements can the defect be characterised and sized uniquely? The full answer to this question is still unclear, but fortunately, in most NDT applications, something definite is known about the possible defect types. This knowledge unlocks the problem and leads to the general approach described here in which array scattering data is compared to simulations of scattering from possible defects. The closest match is then the characterisation result. Here it is shown that using this approach accurate characterisation is possible even for defects that are fractions of a wavelength in size.

In any real ultrasonic array inspection, some noise is always present, and this sets a lower limit on what characterisation performance is possible. But also, as defects become smaller relative to the wavelength, their scattering behaviours become increasingly similar. When taken together, these two pieces of information set limits on the characterisation performance that can be achieved with any linear imaging algorithm.

Recently it has been shown that the same ultrasonic array data that can be used for the above linear imaging and characterisation, also contains information about the nonlinearity of the defects. The nonlinear information encodes new characterisation information such as crack tip closure which is crucial in structural integrity assessments. The exciting prospect is that this new information can be obtained from commercially available array equipment at little additional cost, a rare case of physics giving something for nothing.

Présentations invitées

A venir.