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Proceedings Paper

Time-reversed ultrasonically encoded (TRUE) optical focusing in reflection mode: demonstrations in tissue mimicking phantoms and ex vivo tissue
Author(s): Puxiang Lai; Xiao Xu; Honglin Liu; Yuta Suzuki; Lihong V. Wang
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Paper Abstract

The problem of how to effectively deliver light dynamically to a small volume inside turbid media has been intensively investigated for imaging and therapeutic purposes. Most recently, a new modality termed Time-Reversed Ultrasonically Encoded (TRUE) optical focusing was proposed by integrating the concepts of ultrasound modulation of diffused light with optical phase conjugation. In this work, the diffused photons that travel through the ultrasound focal region are "tagged" with a frequency shift due to the ultrasound modulation. Part of the tagged light is collected in reflection mode and transmitted to a photorefractive crystal, forming there a stationary hologram through interference with a coherent reference optical beam. The hologram is later read by a conjugated optical beam, generating a phase conjugated wavefront of the tagged light. It is conveyed back to the turbid medium in reflection mode, and eventually converges to the ultrasound focal zone. Optical focusing effects from this system are demonstrated experimentally in tissue-mimicking phantoms and ex vivo chicken breast tissue, achieving effective round-trip optical penetration pathlength (extinction coefficient multiplied by round-trip focusing depth) exceeding 160 and 100, respectively. Examples of imaging optical inclusions with this system are also reported.

Paper Details

Date Published: 9 February 2012
PDF: 9 pages
Proc. SPIE 8223, Photons Plus Ultrasound: Imaging and Sensing 2012, 82231B (9 February 2012); doi: 10.1117/12.906017
Show Author Affiliations
Puxiang Lai, Washington Univ. in St. Louis (United States)
Xiao Xu, Washington Univ. in St. Louis (United States)
Honglin Liu, Washington Univ. in St. Louis (United States)
Yuta Suzuki, Washington Univ. in St. Louis (United States)
Lihong V. Wang, Washington Univ. in St. Louis (United States)

Published in SPIE Proceedings Vol. 8223:
Photons Plus Ultrasound: Imaging and Sensing 2012
Alexander A. Oraevsky; Lihong V. Wang, Editor(s)

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