IEEE Gainesville Section Presents 

High-resolution Biophotonic Imaging

Lihong V. Wang, Ph.D. 

Royce E. Wisenbaker II Professor of Engineering, University Faculty Fellow
Director, Optical Imaging Laboratory
Departments of Biomedical Engineering & Electrical Engineering
Texas A&M University

Place: 409 New Engineering Building
Time:  9:00-11:00am, Friday, February 18 


Abstract

We develop novel biophotonic tomography for early-cancer detection and 
functional imaging using physically combined 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, at the same time, reveal new contrast mechanisms.  For example, 
our spectroscopic oblique-incidence reflectometry can detect skin cancers 
accurately based on functional hemoglobin parameters and cell nuclear size.  
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, as demonstrated by confocal microscopy and 
two-photon microscopy as well as optical coherence tomography, is limited 
to superficial imaging within about one transport mean free path (~1 mm) 
into biological tissues.  Ultrasonic imaging, on the contrary, furnishes 
good image resolution but has strong speckle artifacts as well as poor 
contrast in early-stage tumors.  We have developed ultrasound-mediated 
imaging modalities by combining electromagnetic and ultrasonic waves 
synergistically to overcome the above problems.  The hybrid modalities 
yield speckle-free images of high electromagnetic contrast at high 
ultrasonic resolution in relatively large volumes of biological tissues.  
The specific technologies to be reviewed in the talk are summarized below.

Mueller optical coherence tomography provides microscopic-scale 
depth-resolved tomographic images of the complete polarization properties 
in scattering biological tissues.  Polarization properties are related to 
the orientation and density of fibril structures (such as collagen) in skin, 
retina, cartilage, muscle, and other anisotropic biological tissues.  
Potential applications include the imaging of burns, detection of glaucoma, 
study of osteoporosis, and detection of cancer. 

In ultrasound-modulated optical tomography, a focused ultrasonic wave tags 
diffuse laser light in scattering biological tissue, which is analogous to 
the encoding concept in MRI.  Because the tagged photons that carry the 
ultrasonic frequency originate from the localized ultrasonic wave, they 
can be extracted from the observed optical speckles to achieve 
high-resolution tomographic imaging.

In photo-acoustic tomography, an expanded pulsed laser beam diffuses into 
the biological tissue and generates a small but rapid temperature rise, 
which causes the emission of ultrasonic waves as a result of thermoelastic 
expansion.  The short-wavelength ultrasonic waves are then detected to form 
diffraction-limited high-resolution tomographic images.

Thermo-acoustic tomography is similar to photo-acoustic tomography except 
that low-energy radio-frequency pulses, instead of laser pulses, are used.  
Although the long-wavelength radio-frequency waves diffract rapidly in the 
tissue, the short-wavelength ultrasonic waves provide high spatial 
resolution. 


Brief Biography

Dr. Lihong Wang received the Ph.D. degree from a Nobel Prize winning group 
at Rice University, Houston, Texas, in 1992.  He worked first for the 
University of Texas M. D. Anderson Cancer Center, a top-ranked cancer 
institution, as an Assistant Professor.  He then moved to Texas A&M 
University where he was promoted to Professor of Biomedical Engineering and 
Electrical Engineering in 2002.  He was appointed University Faculty Fellow 
and Royce E. Wisenbaker II Endowed Professor of Engineering in 2002 and 2004, 
respectively.  He has published more than 180 scientific articles (90+ in 
peer-reviewed journals, such as Physical Review Letters, Physical Review, 
Optics Letters, and Nature Biotechnology), received 3 patents and has 
delivered more than 90 plenary, keynote, and invited talks.  He has received 
the NIH FIRST award, NSF CAREER award, Texas A&M TEES Select Young Faculty 
award, TEES Faculty Fellow award (twice), TEES Senior Faculty Fellow award, 
and Texas A&M Ernest A. Baetz Faculty Fellow award.  He has served as a grant 
reviewer or study section chair for NIH, NSF, the U.S. Navy, the Whitaker 
Foundation, Australian Research Council, Canadian IHR, Physics Research 
Council of the Netherlands, and other funding agencies.  He has served as 
an associate editor for the Annals of Biomedical Engineering, the Journal 
of Biomedical Optics, and Applied Optics.  He has been a reviewer for 30 
scientific journals.  He is a fellow of the American Institute for Medical 
and Biological Engineering, the Optical Society of America, and the Society 
of Photo-Optical Instrumentation Engineers.  He has organized numerous 
conferences for various societies and received a conference grant from the 
Whitaker Foundation.  He serves on the scientific advisory boards of three 
companies.  His research focus is on non-ionizing biophotonic imaging, which 
has been funded in the amount of $12M by NIH (principal investigator for 
nine grants), NSF, DOD, the Whitaker Foundation, NIST, and other funding 
sources.  His group has pioneered ultrasound-modulated optical tomography, 
spectroscopic oblique-incidence reflectometry, Mueller-matrix optical 
coherence tomography, thermoacoustic tomography and photoacoustic 
tomography.  His Monte Carlo model of photon transport in biological 
tissues has been used worldwide (available at http://oilab.tamu.edu).

For more information, contact Dr Jian Li , 352-392-2642 or by 
e-mail: li@dsp.ufl.edu