Optical Imaging  

Ultrasound-modulated Optical Tomography

Optically, biological tissues to light are much like a glass of milk, where one cannot see a sugar cube in the center of the glass because all of the light is scattered by the milk. Optical imaging of biological tissues overcomes this problem by recovering imaging information from scattered light. Light at selected wavelengths can penetrate 5-10 cm thick biological tissues and provide detectable optical signals. In ultrasound-modulated optical tomography, optical contrast is combined with the spatial resolution of ultrasonic imaging for deep imaging. An ultrasonic wave is focused into turbid media and modulates laser light passing through the ultrasonic field. The modulated laser light contains primarily the local material properties in the focal zone. Raster scanning over the turbid object yields an image of the medium based on the ultrasound-modulated optical signal.

Buried objects in 5-cm thick tissue phantoms can be located with millimeter resolution (see the following figure). This imaging modality has broad applications in biomedicine as well as in breast cancer detection.

Selected publications:

  • Li, Y. Z.; Hemmer, P.; Kim, C. H.; Zhang, H. L.; Wang, L. V.; "Detection of ultrasound-modulated diffuse photons using spectral-hole burning," Optics Express 16(19) 14862-14874 (2008) [PDF]

  • Sakadzic, S.; Wang, L. V.; "Correlation transfer and diffusion of ultrasound-modulated multiply scattered light," Physical Review Letters 96(16) 163902- (1-4) (2006) [PDF]

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

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

  • Wang, L. V.; Ku, G.; "Frequency-swept ultrasound-modulated optical tomography of scattering media," Optics Letters 23(12) 975-977 (1998) [PDF]

  • Wang, L. V.; Jacques, S. L.; Zhao, X. M.; "Continuous-Wave ultrasonic modulation of scattered laser-Light to image objects in turbid media," Optics Letters 20(6) 629-631 (1995) [PDF]

2D image of a tissue phantom.

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