Optical Imaging  

Ultrasound-modulated Optical Tomography

Optically, biological tissues to the light are much like a glass of milk, where one cannot see a sugar cube in the center of the glass because the milk scatters light. Optical imaging of biological tissues overcomes this problem by recovering imaging information from the scattered light. Light at selected wavelengths can penetrate 5-10 cm thick biological tissues and provide detectable optical signals. The Optical Imaging Laboratory has pioneered a technique called ultrasound-modulated optical tomography, in which optical sensitivity is combined with the spatial resolution of ultrasonic imaging.

The goal of this research is to develop a novel, non-ionizing, non-invasive imaging modality for biomedical applications. Ultrasonic modulation of scattered laser light has been used to image objects buried in tissue-simulating turbid media. An ultrasonic wave is focused into the turbid media modulated the laser light passing through the ultrasonic field. The modulated laser light reflected primarily the local mechanical and optical properties in the focal zone. Raster scanning over the turbid object yielded an image of the medium based on the ultrasound-modulated optical signal. Buried objects in 5-cm thick tissue phantoms were located with millimeter resolution (see the following figure). Although this imaging modality has generic applications in biomedicine, we will first test the technique for breast cancer detection.

Selected publications:

  • P. Lai, L. Wang, J. Tay, and L. V. Wang, "Photoacoustically guided wavefront shaping (PAWS) for enhanced optical focusing in scattering media," Nature Photonics 9, advance online publication, doi:10.1038/nphoton.2014.322 (2015). [PDF]

  • Y. Liu, P. Lai, C. Ma, X. Xu, A. A. Grabar, and L. V. Wang, "Optical focusing deep inside dynamic scattering media with near-infrared time-reversed ultrasonically encoded (TRUE) light." Nat. Commun. 6:5904 doi: 10.1038/ncomms6904 (2015). [PDF]

  • C. Ma, X. Xu, Y. Liu, and L. V. Wang, "Time-reversed adapted-perturbation (TRAP) optical focusing onto dynamic objects inside scattering media," Nature Photon., doi:10.1038/nphoton.2014.251(2014). PDF]

  • [X. Xu, H. Liu], and L. V. Wang, “Time-reversed ultrasonically encoded optical focusing into scattering media,Nature Photonics 5, 154-157 (Mar. 2011). Published online on January 16, 2011. [Request PDF]

  • Y. Z. Li, P. Hemmer, C. H. Kim, H. L. Zhang, and L. V. Wang, "Detection of ultrasound-modulated diffuse photons using spectral-hole burning," Optics Express 16, 14862–14874 (Sep. 2008).[PDF]

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  • S. Sakadzic and L.-H. Wang, "Correlation transfer and diffusion of ultrasound-modulated multiply scattered light," Physical Review Letters 96, 163902 (Apr. 2006).[PDF]

  • S. Sakadzic and L.-H. Wang, "High-resolution ultrasound-modulated optical tomography in biological tissues," Optics Letters 29 (23), 2770–2772 (Dec. 1, 2004).[PDF]

  • L.-H. Wang, "Mechanisms of ultrasonic modulation of multiply scattered coherent light: an analytic model," Physical Review Letters 87, 043903-(1–4) (2001). [PDF]

  • L.-H. Wang and G. Ku, "Frequency-swept ultrasound-modulated optical tomography of scattering media," Optics Letters 23, 975-977 (1998). [PDF]

  • L.-H. Wang, S. L. Jacques, and X.-M. Zhao, "Continuous-wave ultrasonic modulation of scattered laser light to image objects in turbid media," Optics Letters 20, 629-631 (1995). [PDF]

2D image of a tissue phantom.

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