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Journal of Biomedical Optics • Open Access

Time-reversed ultrasonically encoded optical focusing using two ultrasonic transducers for improved ultrasonic axial resolution
Author(s): Qiang Yang; Xiao Xu; Puxiang Lai; Daxiong Xu; Lihong V. Wang

Paper Abstract

Focusing light inside highly scattering media is a challenging task in biomedical optical imaging, manipulation, and therapy. A recent invention has overcome this challenge by time reversing ultrasonically encoded diffuse light to an ultrasound-modulated volume inside a turbid medium. In this technique, a photorefractive (PR) crystal or polymer can be used as the phase conjugate mirror for optical time reversal. Accordingly, a relatively long ultrasound burst, whose duration matches the PR response time of the PR material, is usually used to encode the diffuse light. This long burst results in poor focusing resolution along the acoustic axis. In this work, we propose to use two intersecting ultrasound beams, emitted from two ultrasonic transducers at different frequencies, to modulate the diffuse light at the beat frequency within the intersection volume. We show that the time reversal of the light encoded at the beat frequency can converge back to the intersection volume. Experimentally, an acoustic axial resolution of ∼1.1  mm was demonstrated inside turbid media, agreeing with theoretical estimation.

Paper Details

Date Published: 5 November 2013
PDF: 5 pages
J. Biomed. Opt. 18(11) 110502 doi: 10.1117/1.JBO.18.11.110502
Published in: Journal of Biomedical Optics Volume 18, Issue 11
Show Author Affiliations
Qiang Yang, Beijing Univ. of Posts and Telecommunications (China)
Xiao Xu, Washington Univ. in St. Louis (United States)
Puxiang Lai, Washington Univ. in St. Louis (United States)
Daxiong Xu, Beijing Univ. of Posts and Telecommunications (China)
Lihong V. Wang, Washington Univ. in St. Louis (United States)

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