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Three-dimensional, miniature endoscope
opens new diagnostic possibilities
New approach with single optical
fiber may give access to currently unreachable areas.
BOSTON - October 18, 2006 - Massachusetts General Hospital
(MGH) researchers have developed a new type of miniature endoscope
that produces three-dimensional, high-definition images, which may
greatly expand the application of minimally invasive diagnostic
and therapeutic procedures. In the October 19 issue of Nature,
the team from the Wellman
Center for Photomedicine at MGH describes their prototype device
and a demonstration of its use in a mouse model.
"This new ultraminiature endoscope is the first to allow three-dimensional
imaging of areas inside the body, " says Guillermo Tearney,
MD, PhD, of the MGH Wellman Center, the report's senior author.
"Its ability to go places that other imaging tools cannot reach
opens new possibilities for medical diagnosis and eventually treatment."
Standard miniature endoscopic devices - which give physicians access
to hard-to-reach internal organs and structures - utilize bundles
of optical fibers to supply light to and transmit images from the
areas of interest. Larger endoscopes that use image sensors to produce
high-quality, two-dimensional images can be a centimeter or more
in diameter. Existing miniature endoscopes using smaller fiber bundles
may be more flexible but have difficulty producing high-quality
images.
The new device developed at MGH-Wellman uses a technology called
spectrally encoded endoscopy (SEE). Multicolored light from a single
optical fiber - introduced through a probe about the size of a human
hair - is broken into its component colors and projected onto tissue,
with each color illuminating a different part of the tissue surface.
The light reflected back is recorded, and the intensity of the various
colors decoded by a spectrometer, which analyzes the wavelengths
of light. Another device called an interferometer, which calculates
structural information based on the interaction between two waves
of light, provides the data required to create three-dimensional
images.
To demonstrate the device's application in a live animal, the researchers
used the system to image metastatic ovarian tumors on the abdominal
wall of a mouse. The SEE probe was passed into the abdominal cavity
through a fine-gauge needle. The resulting three-dimensional image
showed several raised areas of tumor nodules, the presence of which
was confirmed by histologic analysis of the tissue.
"The most important feature of this new endoscope is the ability
to obtain three-dimensional images, something we don't believe is
offered by any commercially available miniature endoscope system,"
says Dvir Yelin, PhD, first author of the Nature paper. "While
the image resolution we achieved in this demonstration is similar
to existing small-diameter endoscopes, with further optimization
of the optics it is possible to obtain images with 10 times the
number of pixels provided by other miniature endoscopes."
"This new technology will offer physicians and surgeons the
capability to bring many more procedures into outpatient settings,
reduce anesthesia requirements and minimize tissue damage,"
Tearney adds. "The device's size and flexibility should allow
safer navigation through such delicate structures as the salivary
ducts, the fallopian tubes and the pancreatic duct. Fetal and pediatric
procedures may also benefit from this tool. Eventually, SEE could
give rise to new procedures that permit diagnosis and microsurgery
in previously inaccessible areas of the body."
 The
spectral encoded miniature endoscope uses micro optics and a single
optical fiber to project various colors of light onto different
portions of the subject. The light reflected back into the endoscope
is measured and analyzed to produce a three-dimensional image. This
illustration shows a time exposure of white light transmitted through
the miniature endoscope, superimposed on a three-dimensional rendering
of mouse metastatic ovarian tumor nodules obtained with this new
technique.
Tearney is an associate professor of Pathology at Harvard Medical
School. He and his colleagues are working on adapting the SEE device
for human studies in the near future. Additional co-authors of the
Nature report are Imran Rizvi, Matthew White, MD, Jason Motz, PhD,
Tayyaba Hasan, PhD, and Brett Bouma, PhD - all of the Wellman Center.
The research was supported by grants from the Center for the Integration
of Medicine and Innovative Technology, the National Science Foundation
and the Whitaker Foundation.
Massachusetts General Hospital, established in 1811, is the original
and largest teaching hospital of Harvard Medical School. The MGH
conducts the largest hospital-based research program in the United
States, with an annual research budget of nearly $500 million and
major research centers in AIDS, cardiovascular research, cancer,
computational and integrative biology, cutaneous biology, human
genetics, medical imaging, neurodegenerative disorders, regenerative
medicine, transplantation biology and photomedicine. MGH and Brigham
and Women's Hospital are founding members of Partners HealthCare
HealthCare System, a Boston-based integrated health care delivery
system.
Media Contact: Sue
McGreevey, MGH Public Affairs
Physician Referral Service: 1-800-388-4644
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