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(Archives) Jeudi 26 Novembre 2009 à 13h30 (amphi Rouard) - Modern ultrasound imaging: An exciting window into the sub-surface world

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(Archives) Jeudi 26 Novembre 2009 à 13h30 (amphi Rouard) - Modern ultrasound imaging: An exciting window into the sub-surface world

par Francesco Simonetti
Department of Mechanical Engineering, Imperial College, London SW7 2AZ, United Kingdom

Résumé

Progress in solid state electronics and micromachining has led to the rapid development of ultrasound array technology. It is now possible to measure spatial maps of ultrasonic fields almost instantaneously, with high sensitivity and under various insonification conditions. The technology has become central to imaging in combination with beamforming techniques for applications in medical diagnostics and now in NDE for defect characterization. However, the resolution of current beamforming technology is limited. Indeed, it is not possible to observe the sub-wavelength structure of an object due to diffraction as demonstrated by Lord Rayleigh more than a century ago. Although the resolution can in principle be enhanced by decreasing the wavelength, the penetration depth of the probing wave into the object decreases as the frequency increases due to energy dissipation and/or scattering. This talk introduces the notion that ultrasonic measurements encode more information about the object’s structure than beamforming can extract. The key to unlock this information is provided by the knowledge of the scattering mechanism that has caused the encoding in the first instance. This leads to a modern imaging strategy that goes beyond beamforming, can achieve subwavelength resolution and shares some of the underpinning physics with near field microscopy - known to break the Rayleigh criterion. These arguments are supported by experimental images showing unprecedented subwavelength resolution and tomographic reconstructions of a complex 3-D breast phantom that exhibit striking similarities with X-ray CT and first in vivo results unravelling the complex anatomy of the human breast.

Invitation : Anne Sentenac (SEMO)