Abstract
Photoacoustic tomography has been developed for in vivo functional, metabolic, molecular, and histologic imaging by physically combining optical and ultrasonic waves. Broad applications include early-cancer detection and brain imaging. Conventional high-resolution optical imaging of scattering tissue is limited to depths within the optical diffusion limit (~1 mm in the skin). Taking advantage of the fact that ultrasonic scattering is orders of magnitude weaker than optical scattering per unit path length, photoacoustic tomography beats this limit and provides deep penetration at high ultrasonic resolution and high optical contrast. The annual conference on photoacoustic tomography has become the largest in SPIE’s 20,000-attendee Photonics West since 2010.
Wavefront engineering overcomes the optical diffusion limit by actively controlling the wavefront of the incident light to optimize the light intensity at a target position inside tissue. One such technology is called time-reversed ultrasonically encoded (TRUE) optical focusing, which can noninvasively deliver light to a dynamically defined focus deep in a scattering medium. First, diffused coherent light is encoded by a focused ultrasonic wave to provide a virtual internal “guide star”; then, only the encoded light is time-reversed and transmitted back to the ultrasonic focus.
Compressed ultrafast photography (CUP) can image in 2D non-repetitive time-evolving events at up to 100 billion frames per second. CUP has a prominent advantage of measuring an x, y, t (x, y, spatial coordinates; t, time) scene with a single camera snapshot, thereby allowing observation of transient events occurring on a time scale down to tens of picoseconds. Further, akin to traditional photography, CUP is receive-only—avoiding specialized active illumination required by other single-shot ultrafast imagers. Given CUP’s capability, it is expected to find widespread applications in both fundamental and applied sciences including biomedical research.
About the speaker
Prof Lihong Wang received his MS and PhD from Huazhong University of Science & Technology and Rice University in 1987 and 1992 respectively. He had been affiliated with the University of Texas M.D. Anderson Cancer Center and Texas A&M University before joining the Washington University in St. Louis, where he is currently the Gene K. Beare Distinguished Professor of Biomedical Engineering.
Prof Wang’s research focuses on photoacoustic tomography, 3D photoacoustic microscopy, ultrasound-modulated optical tomography, Mueller-matrix optical coherence tomography, microwave-induced thermoacoustic tomography and, Monte Carlo simulation of photon transport.
Prof Wang was elected a Fellow of the AIMBE, OSA, IEEE, and SPIE. He is the Editor-in-Chief of the Journal of Biomedical Optics. He received NIH's FIRST, NSF's CAREER, NIH Director's Pioneer, and NIH Director's Transformative Research awards. He also received the OSA C.E.K. Mees Medal, IEEE Technical Achievement Award, IEEE Biomedical Engineering Award, and SPIE Britton Chance Biomedical Optics Award for "seminal contributions to photoacoustic tomography and Monte Carlo modeling of photon transport in biological tissues." His book entitled “Biomedical Optics: Principles and Imaging” won the Joseph W. Goodman Book Writing Award.
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