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
2Why 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.
3Why 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.
42 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
5microscopic 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.
7A 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.
8Cardiovascular 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.
11Cancer 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.
13Microscopy
- 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
14What 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.
16OCT 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.
17Comparison between OCT (left) and Ultrasound
(right).
Comparison between OCT (left) and Ultrasound
(right). Tearney, G.J., et. al. Circ. 4256,
1997
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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
19Electronic 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
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24Advantages 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.
25Advantages 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 27Wigner transformation
28Model 1
- The first model is a cos-function with gaussian
29Wigner transformation of 2 signals with different
parameters (Re)
30Wigner transformation of 2 signals with same
parameters (Re)
31Wigner transformation of 2 signals with different
parameters (Im)
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32Model 2
Signal Linear frequency modulation
33Wigner transformation of 2 signals with same
parameters (Re)
34Wigner transformation of 2 signals with different
parameters (Re)
35Wigner transformation of 2 signals with different
parameters (Im)
36