Beckman Laser Institute
Department of Biomedical Engineering
1002Health Sciences Road East
University of California, Irvine
Irvine, CA 92612
Phone: 949-824-1247
Fax: 949-824-8413
Email: z.chen@uci.edu
Optical Coherence Tomography and
Microendoscopic Multiphoton Tomography
Zhongping Chen, Ph.D.
Department of Biomedical Engineering, Beckman Laser
Institute
University of California, Irvine, Irvine, CA 92612
Abstract: The development of a Fourier domain optical coherence
tomography that achieves high speed and high resolution simultaneously
is described. In addition, a fiber based multiphoton system that provide
molecular contrast for in vivo imaging will be discussed.
Summary
Optical coherence tomography (OCT) is a recently developed imaging
modality based on coherence-domain optical technology.
OCT takes
advantage of the short coherence length of broadband light sources to
perform micrometer-scale, cross-sectional imaging of biological tissue.
OCT is analogous to ultrasound imaging except that it uses light rather
than sound.
The high spatial resolution of OCT enables noninvasive in
vivo “optical biopsy” and provides immediate and localized diagnostic
information.
The first in vivo endoscopic OCT images in animals and
humans were reported in 1997.
Since then, a number of clinical
applications for endoscopic OCT imaging of respiratory, urogenital, and GI
tracts have been reported by several groups.
Most current OCT
applications use time domain (TD) systems with limited speed and
sensitivity. However, many clinical applications require a large area or 3D imaging, which is difficult to achieve with TD OCT.
The recent
development of Fourier domain (FD) OCT has attracted much attention
because of its potential high speed and sensitivity.
The significant
increase in imaging speed and sensitivity makes it possible to obtain 3-D
images in real time.
Although high speed endoscopic FD OCT has recently been demonstrated
by several groups, few endoscopic clinical applications that combine high
speed with high spatial resolution have been reported. This is because a
number of obstacles exist for a wide adoption of the technology for clinical
application.
First, the current commercial swept source has limited
wavelength scanning speed (28 kHz) and bandwidth (3 dB FWHM of
approximately 100 nm). While 28 kHz is high enough for real time 2-D
imaging, there are many clinical applications that require 3-D imaging
with even faster speed.
In addition, the available bandwidth in
commercial devices limit the axial
speed requires a scanning probe with increased speed and 2-D scanning
capability. While several 2-D MEMS scanners for OCT have been reported,
few have been packaged into a compact endoscopic form for clinical
applications.
Third, although axial resolution is determined by the
scanning bandwidth of the source, there is a trade-off between imaging
depth range and lateral resolution.
High lateral resolution can only be
achieved in a small depth of the focal region.
We will report the latest development an OCT system that overcomes
these
limitations
simultaneously.
and
achieves
high
speed
and
high
resolution
We will describe the development of a Fourier-domain-
mode-lock (FDML) swept source that provides high speed (>100 kHz Ascan rate) and high spatial resolution (< 4 mm) simultaneously (1). In
addition, we will report the development of a 2-D MEMS scanner for an
endoscopic probe that allows high speed 3-D OCT imaging (2-5).
Furthermore, we will describe a number of applications of OCT in various
fields, including quantification of micro-fluidics and diagnosis of cancers
and vascular diseases. Finally, we will describe a fiber based multiphoton
system that can provide molecular contrast for in vivo imaging (6).
Acknowledgments
This work is supported by the National Institutes of Health (EB-00293,
NCI-91717, RR-01192), and the Air Force Office of Science Research
(FA9550-04-1-0101).
Institutional support from the Beckman Laser
Institute and Medical Clinic is also gratefully acknowledged.
References
1.
2.
3.
4.
5.
6.
Jeon, M. Y., J. Zhang, Q. Wang, and Z. Chen. 2008. High-speed and wide bandwidth Fourier domain
mode-locked wavelength swept laser with multiple SOAs. Optics Express 16:2547-2554.
Su, J., J. Zhang, L. Yu, and Z. Chen. 2007. in vivo three-dimensional microelectromechanical
endoscopic swept source optical coherence tomography. Optics Express 15:10390-10396.
Su, J., J. Zhang, L. Yu, G. C. H, M. Brenner, and Z. Chen. 2008. Real-time swept source optical
coherence tomography imaging of the human airway using a microelectromechanical system endoscope
and digital signal processor. J Biomed Opt 13:030506.
Jung, W. G., J. Zhang, L. Wang, Z. Chen, D. T. McCormick, and N. C. Tien. 2006. Three-dimensional
endoscopic optical coherence tomography by use of a two-axis microelectromechanical scanning
mirror. Applied Physics Letters 88:163901-163903.
Jung, W., D. T. McCormick, Y. C. Ahn, A. Sepehr, M. Brenner, B. Wong, N. C. Tien, and Z. Chen.
2007. In vivo three-dimensional spectral domain endoscopic optical coherence tomography using a
microelectromechanical system mirror. Opt Lett 32:3239-3241.
Jung, W., S. Tang, D. T. McCormic, T. Xie, Y. C. Ahn, J. Su, I. V. Tomov, T. B. Krasieva, B. J.
Tromberg, and Z. Chen. 2008. Miniaturized probe based on a microelectromechanical system mirror for
multiphoton microscopy. Opt Lett 33:1324-1326.
Brief Biography:
Dr. Zhongping Chen is a Professor and Vice Chair of Department of Biomedical Engineering
at University of California, Irvine. He is a Co-Founder of OCT Medical Imaging Inc.. Dr.
Chen received his B.S. degree in Applied Physics from Shanghai Jiao Tong University in
1982, his M. S. degree in Electrical Engineering from Cornell University in 1987, and his
Ph.D. degree in Applied Physics from Cornell University in 1993.
Dr. Chen’s research interests encompass the areas of biomedical photonics, microfabrication,
biomaterials and biosensors. His research group has pioneered the development of functional
optical coherence tomography, which simultaneously provides high resolution 3-D images of
tissue structure, blood flow, and birefringence. He has published more than 120 peerreviewed papers and review articles and holds a number of patents in the fields of
biomaterials, biosensors, and biomedical imaging.
Dr. Chen is a Fellow of the American Institute of Medical and Biological Engineering
(AIMBE), a Fellow of SPIE, and a Fellow of the Optical Society of America.
Current Position:
Professor Department of Biomedical Engineering, and Director of Functional OCT
Laboratory, Beckman Laser Institute, University of California, Irvine.