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Computer signal transmission in optical coherence tomography on the basis of Wigner transformation

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Title: Computer signal transmission in optical coherence tomography on the basis of Wigner transformation


1
  • Computer signal transmission in optical coherence
    tomography on the basis of Wigner transformation
  • JASS-2004 ,
  • St.-Petersburg

2
Why Use OCT?
  • For more than three centuries, the microscope has
    been considered the ultimate tool to understand
    the origins of disease by examining tissue and
    microstructures in exquisite detail.

3
Why use OCT?
  • While the technology contained within the
    microscope has evolved over time, enabling better
    resolution of smaller structures, one aspect has
    remained constant - material to be examined must
    be excised from the body and brought to the
    microscope.

4
2 main reasons
  • New thinking concerning the origins of the
    world's two largest killers
  • heart disease and cancer
  • expose the limitations of the current paradigm.
    Both diseases are thought to originate at the
    cellular level in the thin (20 - 200 micron)
    cellular layer covering the inner and outer
    surfaces of the body. Understanding these
    diseases on the microscopic level on an in vivo
    basis could lead to better diagnosis, earlier
    more precise treatments and development of novel
    therapies to help eradicate these diseases

5
microscopic images from within the body
  • For years, scientists, physicians and technology
    developers have struggled to achieve microscopic
    images from within the body. These attempts have
    met with limited success due to two primary
    factors
  • the size of the apparatus being deployed and
  • the resolution of the images being obtained.

6
  • Attempts to obtain microscopic images using
    external methodologies
  • magnetic resonance,
  • X-ray, ultrasound, and
  • nuclear imaging,
  • have met with similar fates.

7
A New Weapon for Heart Disease and Cancer
  • While OCT has the potential to be used for a
    variety of medical applications, cancer and heart
    disease represent two of the most pressing, and
    promising application areas.

8
Cardiovascular Imaging
  • OCT imaging has the potential to improve current
    cardiovascular therapies such as stenting and
    balloon angioplasty, by providing vascular images
    in real time to guide stent placement and balloon
    inflation. Given its small size, the OCT imaging
    guidewire could be integrated into an existing
    therapeutic catheter or deployed alongside during
    a procedure.

9
  • New cardiac research indicates that unstable
    plaques - arterial lesions that do not constrict
    the blood vessel but rather burst releasing a
    bolus of lipids into the blood stream - may be
    responsible for up to 70 percent of all heart
    attacks. OCT has the potential to clearly
    identify plaques and help differentiate unstable
    plaques from stable plaques.
  • Cardiovascular System Atherosclerotic Disease
    Brezinski, M.E. Circ. 93 12061996

10
  • In addition to providing exquisite morphological
    detail, OCT is meeting other capabilities such as
    spectroscopic imaging, polarization imaging and
    Doppler to provide further information regarding
    tissue composition and flow.

11
Cancer Detection
  • It is estimated that more than 85 percent of all
    cancers originate in the epithelium, the thin
    (20-200 micron) cellular layer covering the inner
    and outer surfaces of the body. Excisional
    biopsy, removing tissue from the body and
    examining it under a microscope, is the gold
    standard for cancer diagnosis. However, many
    biopsies are done on a hit or miss basis, small
    pieces of tissue are excised at random and
    dissected to check for cancerous cells.

12
  • OCT has the potential to greatly improve
    conventional biopsy by more precisely identifying
    the areas to be excised based on images of the
    epithelial layers, reducing the number of
    biopsies and making earlier and more accurate
    diagnosis possible. As the technology matures, it
    may be possible to perform biopsies using OCT
    imaging alone, making possible point of care
    biopsy.

13
Microscopy
  • OCT offers the potential to assist in the
    visualization of vessels and nerves for repair
    surgery. OCT may also have the potential for
    identifying the margins of low-grade invasive
    neurological tumors. The use of OCT imaging
    forceps may be beneficial to many microsurgical
    procedures.

Intestinal polyps Ex Vivo Human Tissue
14
What is OCT?
  • Optical Coherence Tomography (OCT) is a promising
    new class of diagnostic medical imaging
    technology that utilizes advanced photonics and
    fiber optics to obtain images and tissue
    characterization on a scale never before possible
    within the human body.

15
  • When fully exploited, the technology has the
    potential to dramatically change the way
    physicians, researchers and scientists see and
    understand the human body in order to better
    diagnose and treat disease.

16
OCT and Ultrasound
  • Simply put, OCT combines the principles of
    ultrasound with the imaging performance of a
    microscope and a form factor that is familiar to
    clinicians.
  • Whereas ultrasound produces images from
    backscattered sound "echoes,"
  • OCT uses infrared light waves that reflect off
    the internal microstructure within the biological
    tissues. The frequencies and bandwidths of
    infrared light are orders of magnitude higher
    than medical ultrasound signals -- resulting in
    greatly increased image resolution - 8-25 times
    greater than any existing modality.

17
Comparison between OCT (left) and Ultrasound
(right).
Comparison between OCT (left) and Ultrasound
(right). Tearney, G.J., et. al. Circ. 4256,
1997
18
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  • Infrared light is delivered to the imaging site
    through a single optical fiber only .006"
    diameter (about the size of the period in this
    sentence). The imaging guidewire contains a
    complete lens assembly to perform a variety of
    imaging functions. The guidewire can be deployed
    independently or integrated into existing
    therapeutic or imaging catheters

19
Electronic and interferometric techniques
  • While standard electronic techniques are adequate
    for processing ultrasonic echoes that travel at
    the speed of sound, interferometric techniques
    are required to extract the reflected optical
    signals from the infrared light used in OCT.
  • The output, measured by an interferometer, is
    computer processed to produce high-resolution,
    real time, cross sectional or 3-dimensional
    images of the tissue. This powerful technology
    provides in situ images of tissues at near
    histological resolution without the need for
    excision or processing of the specimen.

20
  • In addition to providing high-level resolutions
    for the evaluation of microanatomic structures
    OCT is inherently able to provide information
    regarding tissue composition. Using spectroscopy,
    users can evaluate the spectral absorption
    characteristics of tissue while simultaneously
    determining the orderliness of the tissue through
    the use of polarization imaging

21
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24
Advantages of OCT
  • HIGH RESOLUTION Current OCT systems have
    resolutions at 4-20 um compared to 110 um for
    high frequency ultrasound.
  • TISSUE CHARACTERIZATION Using information
    inherent to the returning photon signals, OCT can
    perform both spectroscopic and polarization
    imaging to better evaluate the composition of
    tissues and lesions.

25
Advantages of OCT
  • SMALL SIZE The fiber-based design allows easy
    integration with small catheter/endoscopes.
  • REAL TIME IMAGING Imaging is at or near real
    time.
  • DOPPLER IMAGING Capable of simultaneous imaging
    and real time flow measurements.

26

27
Wigner transformation
28
Model 1
  • The first model is a cos-function with gaussian

29
Wigner transformation of 2 signals with different
parameters (Re)
30
Wigner transformation of 2 signals with same
parameters (Re)
31
Wigner transformation of 2 signals with different
parameters (Im)
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    (?????? ?????) ??? ??????? ??????????

32
Model 2
Signal Linear frequency modulation
33
Wigner transformation of 2 signals with same
parameters (Re)
34
Wigner transformation of 2 signals with different
parameters (Re)
35
Wigner transformation of 2 signals with different
parameters (Im)
36
  • Thank you!!!
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