Transcript Slide 1

Swept Source Frequency Domain Optical
Coherence Tomography
Anurag Gupta
University of Rochester, BS: Biomedical Engineering
Dr. Zhongping Chen, Dr. Jun Zhang and Dr. Qiang Wang
The University of California, Irvine
Department of Biomedical Engineering
Beckman Laser Institute and Medical Clinic
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Outline
1. Define OCT
2. Clinical Applications
3. Advantage of OCT Over Other Imaging Modalities
4. Types of OCT Systems
5. Motivations for Designing an FDOCT Imaging Modality
6. Sample OCT Image
7. Acknowledgements
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What Is Optical Coherence Tomography?
As Defined in 2005 by the Inventor, Dr. James Fujimoto:
“Optical coherence tomography (OCT) is an emerging imaging
modality which can generate high resolution, cross-sectional images
of microstructure in biological systems...by measuring the echo time
delay of optical backscattering in the tissue as a function of
transverse position.”
http://www.fitzpatrick.duke.edu/Events/Seminars/2005SpringSeminars/Fujimoto.html
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Clinical Applications
• Ophthalmology
–
Diagnosing retinal diseases and other
abnormalities of the eye
• Dermatology
–
–
Early detection of skin cancer
Diagnosing skin diseases and other problems
• Cardiovascular
–
Imaging of the blood vessels and other
cardiovascular areas for early detection of
diseases
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Advantage of OCT
Standard
clinical
Resolution (log)
1 mm
High
frequency
100 µm
Ultrasound
10 µm
Confocal
microscopy
OCT
1 µm
Penetration depth (log)
1 mm
1 cm
10 cm
http://www.risoe.dk/ofd/oct/OCT_apps.htm
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Histology Versus “Optical” Biopsy of a
Normal Hamster Cheek Pouch
Woonggyu Jung, Jun Zhang, Jungrae Chung, Petra Wilder-Smith, Matt Brenner, J. Stuart Nelson, and Zhongping
Chen. "Advances in Oral Cancer Detection Using Optical Coherence Tomography." IEEE JOURNAL OF
SELECTED TOPICS IN QUANTUM ELECTRONICS 11.4 (2005): 811-817. July-Aug. 2006
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<http://chen.bli.uci.edu/publications/J83_Cancer%20IEEE.pdf>.
Size of OCT Device
OCT can be designed to be: compact, portable, relatively
inexpensive, and can be easily connected to any number of
image acquisition scanners
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This is a picture of our system in final stages
Time Domain OCT
Frequency Domain OCT
Stationary
mirror
Mirror
Beam splitter
Beam splitter
Sample
Sample
SLD
Photodetector
Scanning Reference Mirror
Swept
Source
Photodetecter
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Elimination of Scanning Mirror
Swept Source Laser System
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http://www.santec.com/pdf/lasers/HSL-2000.pdf
Motivations
Can You Have a Signal Without Noise?
NO!
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Signal to Noise Ratio (SNR)
• A High SNR Ratio: Higher Image
Quality
– Images are more distinguishable
• A Low SNR Ratio: Lower Image
Quality
– Images are less distinguishable
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SNR of FDOCT Versus TDOCT
FDOCT: acquire signal in the time window of T
Signal term # of photons =
Noise term # of photons =
Fei Wang
EE131 Presentation at Caltech
Where N is the # of pixels per depth scan
We see that the SNR of FDOCT is N times better than that of TDOCT
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Dispersion Control
Dispersion is the separation of white or compound light into
its respective colors, as in the formation of a spectrum by a
prism.
http://en.wikipedia.org/wiki/Dispersion_(optics)
This can cause the resolution of an image to decrease. In
FDOCT, Dispersion can be controlled rather easily whereas
in other imaging modalities its very difficult.
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Before Dispersion Control
18000
16000
14000
Intensity (a.u.)
12000
10000
8000
6000
40 - 50 µm
Resolution
4000
2000
0
-2000
200
400
600
800
1000
1200
1400
1600
1800
2000
Depth (Microns)
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After Dispersion Control
1.20E+009
1.00E+009
Intensity (a.u.)
8.00E+008
6.00E+008
4.00E+008
2.00E+008
8 µm Resolution
0.00E+000
200
400
600
800
1000
1200
1400
1600
1800
2000
Depth (microns)
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Image Acquisition Speed
• Programmed Using Microsoft Visual C++
• Speed: 15 / 16 Frames Per Second
– Images can be Acquired In-Vivo or Ex-Vivo
• This makes it a viable option for use during surgery
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3D Image Acquisition Scanner
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This is a picture of our 3D Image Acquisition Scanner
3D Image Acquisition Scanner Movie
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3D FDOCT Movie of the Retina
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Acknowledgments
The National Science Foundation
The University of California, Irvine (UROP)
Dr. Zhongping Chen, Dr. Jun Zhang, Dr. Qiang Wang,
and Mr. Bin Rao
The Beckman Laser Institute and Medical Clinic
The Air Force Research Laboratory
The IM-SURE Fellows
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