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Proceedings Paper

Experimental investigation of time-reversal of photo-acoustic waves
Author(s): Emmanuel Bossy; Gabriel Montaldo; Michael Tanter; Benoit Forget; François Ramaz; Mathias Fink; Claude Boccara
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Paper Abstract

Ultrasound focusing through complex media can be achieved using time-reversal techniques. These techniques make use of back-propagating ultrasonic waves generated by localized sources. Such sources generally consist of high acoustic contrasts echoing ultrasonic waves generated by an incident ultrasonic field, or directly by point-like transducers inserted at the desired focusing location. In this work, we experimentally investigate time-reversal of acoustic waves generated by photo-acoustic emission. A frequency-doubled Q-switched Nd:YAG laser was used to illuminate phantom with 5-ns laser pulses. A 128-element ultrasonic transducer array, with a center frequency of 1.5 MHz, was used to detect acoustic waves generated by optically absorbing targets suspended in water. A dedicated 32-channel electronics was used to time-reverse and re-emit the detected ultrasonic field. Gel spheres dyed with India ink (diameter approximately 1-2 mm)illuminated by the laser beam were used to generate the photo-acoustic waves. Time-reversal of the detected field was performed to focus ultrasound in the presence of highly defocusing media in front of the transducer array. We demonstrate how this allows correcting for the aberration in order to provide good quality images in the isoplanetic region surrounding the photo-acoustic source.

Paper Details

Date Published: 6 March 2006
PDF: 7 pages
Proc. SPIE 6086, Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics, 60860X (6 March 2006); doi: 10.1117/12.646132
Show Author Affiliations
Emmanuel Bossy, Lab. d'Optique Physique, ESPCI, CNRS, Univ. Paris (France)
Gabriel Montaldo, Lab. Ondes et Acoustique, ESPCI, CNRS, Univ. Paris (France)
Michael Tanter, Lab. Ondes et Acoustique, ESPCI, CNRS, Univ. Paris (France)
Benoit Forget, Lab. d'Optique Physique, ESPCI, CNRS, Univ. Paris (France)
François Ramaz, Lab. d'Optique Physique, ESPCI, CNRS, Univ. Paris (France)
Mathias Fink, Lab. Ondes et Acoustique, ESPCI, CNRS, Univ. Paris (France)
Claude Boccara, Lab. d'Optique Physique, ESPCI, CNRS, Univ. Paris (France)


Published in SPIE Proceedings Vol. 6086:
Photons Plus Ultrasound: Imaging and Sensing 2006: The Seventh Conference on Biomedical Thermoacoustics, Optoacoustics, and Acousto-optics
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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