Photoacoustic Tomography: Beat Optical Diffusion and Diffraction

Friday, December 6, 2013 - 2:00pm
Fung Auditorium | Powell-Focht Bioengineering Hall
Lihong V. Wang

Optical Imaging Lab, Department of Biomedical Engineering

Washington University, St. Louis

Photoacoustic Tomography: Beat Optical Diffusion and Diffraction

 We develop photoacoustic imaging technologies for in vivo early-cancer detection and functional, metabolic, molecular, and histologic imaging by physically combining non-ionizing electromagnetic and ultrasonic waves. Unlike ionizing x-ray radiation, non-ionizing electromagnetic waves—such as optical and radio waves—pose no health hazard and reveal new contrast mechanisms. Unfortunately, electromagnetic waves in the non-ionizing spectral region do not penetrate biological tissue in straight paths as x-rays do. Consequently, high-resolution tomography based on non-ionizing electromagnetic waves alone—such as confocal microscopy, two-photon microscopy, and optical coherence tomography—is limited to superficial imaging within approximately one optical transport mean free path (~1 mm in the skin) of the surface of scattering tissue. Ultrasonic imaging, on the contrary, provides good image resolution but suffers strong speckle artifacts as well as poor contrast in early-stage tumors. Ultrasound-mediated imaging modalities that combine electromagnetic and ultrasonic waves can synergistically overcome the above limitations. The hybrid modalities provide relatively deep penetration at high ultrasonic resolution and yield speckle-free images with high electromagnetic contrast.

 Lihong Wang earned his Ph.D. degree at Rice University, Houston, Texas.  He currently holds the Gene K. Beare Distinguished Professorship of Biomedical Engineering at Washington University in St. Louis. Professor Wang has published 342 peer-reviewed journal articles and delivered 370 keynote, plenary, or invited talks. His Google Scholar h-index and citations have reached 81 and over 26,000, respectively. His laboratory invented or discovered functional photoacoustic tomography, 3D photoacoustic microscopy (PAM), the photoacoustic Doppler effect, photoacoustic reporter gene imaging, focused scanning microwave-induced thermoacoustic tomography, the universal photoacoustic or thermoacoustic reconstruction algorithm, frequency-swept ultrasound-modulated optical tomography, time-reversed ultrasonically encoded (TRUE) optical focusing, sonoluminescence tomography, Mueller-matrix optical coherence tomography, optical coherence computed tomography, and oblique-incidence reflectometry. His Monte Carlo model of photon transport in scattering media is used worldwide. Professor Wang is a Fellow of the AIMBE (American Institute for Medical and Biological Engineering), IEEE (Institute of Electrical and Electronics Engineers), OSA (Optical Society of America), and SPIE (Society of Photo-Optical Instrumentation Engineers). He is the Editor-in-Chief of the Journal of Biomedical Optics. He chairs the annual conference on Photons plus Ultrasound, and chaired the 2010 Gordon Conference on Lasers in Medicine and Biology and the 2010 OSA Topical Meeting on Biomedical Optics. He is a chartered member on an NIH Study Section. He received NIH’s FIRST, NSF’s CAREER, and NIH Director’s Pioneer awards. He was awarded the OSA C.E.K. Mees MedalIEEE Technical Achievement Award, and IEEE Biomedical Engineering Award for “seminal contributions to photoacoustic tomography and Monte Carlo modeling of photon transport in biological tissues and for leadership in the international biophotonics community.”