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Published July 2013 | Accepted Version + Supplemental Material
Journal Article Open

Focused fluorescence excitation with time-reversed ultrasonically encoded light and imaging in thick scattering media


Scattering dominates light propagation in biological tissue, and therefore restricts both resolution and penetration depth in optical imaging within thick tissue. As photons travel into the diffusive regime, typically 1 mm beneath human skin, their trajectories transition from ballistic to diffusive due to the increased number of scattering events, which makes it impossible to focus, much less track, photon paths. Consequently, imaging methods that rely on controlled light illumination are ineffective in deep tissue. This problem has recently been addressed by a novel method capable of dynamically focusing light in thick scattering media via time reversal of ultrasonically encoded (TRUE) diffused light. Here, using photorefractive materials as phase conjugate mirrors, we show a direct visualization and dynamic control of optical focusing with this light delivery method, and demonstrate its application for focused fluorescence excitation and imaging in thick turbid media. These abilities are increasingly critical for understanding the dynamic interactions of light with biological matter and processes at different system levels, as well as their applications for biomedical diagnosis and therapy.

Additional Information

© 2013 Astro Ltd. Received 27 February 2013; Accepted for publication 11 March 2013; Published 15 May 2013. We would like to thank Nitto Denko Technical (Oceanside, CA, USA) for providing the photorefractive polymer for this research. This work was sponsored in part by the National Academies Keck Futures Initiative grant IS 13 and National Institute of Health grants DP1 EB016986 (NIH Director's Pioneer Award), R01 EB000712 and U54 CA136398.

Attached Files

Accepted Version - nihms-511494.pdf

Supplemental Material - lpl10_075604_Suppl_Figure1.tiff

Supplemental Material - lpl10_075604_Suppl_Figure2.tiff

Supplemental Material - lpl10_075604_Suppl_Figure3.tiff

Supplemental Material - lpl10_075604_movie1.avi


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August 19, 2023
October 20, 2023