Caractérisation des milieux mous par optoélastographie transitoire

Abstract : In this work, we studied a method for characterizing soft media based on the combination of optical and mechanical waves. This method is based on an optical detection of a transient motion generated via the acoustic radiation force, at depth in optically diffusive soft media. The motion consists of an initial displacement at the ultrasound focal region, propagating away as a shear wave. The detection is based on the illumination of the investigated medium with coherent light. The light is strongly scattered in the medium, and the transmitted light produces speckle patterns. By use of a fast millionpixel camera (2 kHz), we record speckle patterns before and during the transient motion. Then we calculate spatial correlations between speckle patterns over time. Thanks to its excitation and detection mode, this technique was proven sensitive to both optically absorbing regions and regions with contrast in shear modulus. Moreover, images of both types of contrasts were obtained, with millimetric resolution for shear modulus inclusions. The experimental study and its interpretation was supported by a model coupling a propagation model of elastic waves generated by the acoustic radiation force based on Green's functions, and a propagation model for optical waves in turbid media.
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Submitted on : Monday, December 20, 2010 - 12:08:00 PM
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Khalid Daoudi. Caractérisation des milieux mous par optoélastographie transitoire. Optique [physics.optics]. Université Pierre et Marie Curie - Paris VI, 2009. Français. 〈pastel-00548741〉

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