Back to Surgery Articles
Monday 12th June, 2006
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3-D ultrasound probes built by
researchers at Duke's Pratt School of Engineering
could give surgeons a better view.
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Biomedical engineers in the United States at Duke
University's Pratt School of Engineering have created a new
three-dimensional ultrasound imaging probe.
In a peer-reviewed report published in the journal Ultrasonic
Imaging, issued in late March 2006, researchers at Duke's Pratt
School of Engineering discussed the results of the new 3D
ultrasound device that they say is poised to advance minimally
invasive surgery.
Endoscopy is a minimally invasive diagnostic medical procedure
used to evaluate the interior surfaces of an organ by inserting
a small scope in the body, often but not necessarily through a
natural body opening. Through the scope, one is able to see
lesions.
?Endoscopy is an instrument that not only provides an image but
also enables taking small biopsies?, says Dr Mihai Mavru,
Primary surgeon - Caritas University Hospital, Romania. ?In
addition endoscopy allows for foreign object retrieval and even
quite sophisticated surgery. Endoscopy is the vehicle for
minimally invasive surgery?, says Dr. Mavru.
Endoscopic surgery has the advantage of reduced postoperative
pain and a faster recovery. However, the two-dimensional
ultrasound imaging now available offers surgeons only a limited
view, which can impede their depth perception and make such
procedures difficult to master.
Biomedical engineering professor Stephen Smith, who specializes
in ultrasound imaging and his team, including biomedical
engineering graduate student Chris Pua, developed the probe
specifically for use in hospitals and clinics.
The engineers said their demonstration showed that the new 3D
ultrasound probes could give surgeons a better view during human
endoscopic surgeries in which operations are performed through
tiny "keyhole" incisions.
Surgeons now use optical endoscopes or two-dimensional
ultrasound when conducting minimally invasive surgery. Optical
endoscopes are thin tubes with a tiny video camera that surgeons
can insert directly into the abdomen or chest through small
incisions.
The current advance relies on 504 tiny cables and sensors. Each
sensor is as wide as a few human hairs. The cables and sensors
are packed into a tube 12 millimeters in diameter ?- the size
required to fit into surgical instruments, called trocars, that
surgeons use to allow easy exchange of laparoscopic tools. By
comparison, most two-dimensional ultrasound probes use just 64
cables.
Each cable carries electrical signals from the scanner to the
sensors at the tip of the tube, which in turn send pulses of
acoustic waves into the surrounding tissue. The sensors then
pick up the returning echoes and relay them back to the scanner
where they produce an image of the moving tissue or organ. The
scanner uses parallel processing to listen to echoes of each
pulse in 16 directions at once.
The probe generates ultrasound at 5 million vibrations per
second, which, combined with the 504 sensors, provides great
sensitivity and a sharp image.
More cables translate into better image quality. The scanners
achieve a 3D moving image instantaneously, with no
reconstruction.
With this scanner, doctors can see the target lesion or a
portion of an organ in a real-time three-dimensional scan. They
would have the option of viewing the tissue in three
perpendicular cross-sectional slices simultaneously or in the
same way a camera would see it ?- except that a camera can't see
through blood and tissue.
The technology has yet to be tested in human patients, but its
success in preclinical experiments makes it ready for clinical
trials, according to the researchers.
In order to demonstrate this possible use, the researchers
produced real-time 3D images of a dog's right pulmonary veins -?
sites that are targeted in treating atrial fibrillation.
The laparoscopic ultrasound probes may be particularly useful
for monitoring heart function during minimally invasive cardiac
surgery. Current methods often monitor the heart with a 2D
ultrasound endoscope probe down the throat, a method known as
transesophageal echocardiography (TEE). This procedure requires
general anesthesia. The images can reveal the condition of the
heart chambers, valves, major blood vessels and heart tissue.
TEE is a safe and fast diagnostic technique.
The new probe, when inserted inside the esophagus, creates a
picture of the whole heart in the time it takes for current
ultrasound technology to image a single heart cross section.
This limitation makes it impractical for use in guiding
therapeutic treatment devices such as ablation probes that burn
off damaged cells that cause an irregular heart beat. In such
procedures, cardiologists use catheters to burn specific
locations on the surface of the heart in patients with atrial
fibrillation, a disorder characterized by an abnormal heart
rhythm. Clinicians must repeatedly and painstakingly reposition
the 2-D probe during treatments so, instead, they use
fluoroscopy (X-ray movies) to guide the placement of the
treatment devices. However, the use of X-ray imaging results in
radiation exposure for patients and requires bulky
lead-shielding garments for clinicians. In addition, such
procedures take up to seven hours to complete.
If physicians instead used the new laparoscopic ultrasonography
imager, they could monitor function for hours through a tiny
incision -? possibly without anesthesia.
Three-D ultrasound is already an established technology in many
hospitals. However, the new real-time 3-D transesophageal probe
has all the benefits of the 2-D TEE probe and none of the
drawbacks. Doctors will be able to generate sharp, high-contrast
images of the whole heart and position heart catheters and
ablation devices at the same time. This is what the team says it
has already achieved in laboratory tests on animals.
Duke developed the first 3D ultrasound scanner in 1987 for
imaging the heart from outside the body. As technology enabled
ever smaller ultrasound arrays, the researchers engineered
probes that could fit inside catheters threaded through blood
vessels to image the vasculature and heart from the inside out.
Similar 3D ultrasound devices also hold promise for minimally
invasive abdominal and brain surgery applications.
The research is funded by the Heart, Lung and Blood Institute at
the National Institutes of Health and by the National Science
Foundation.
By: Dr. Tamer Fouad,
Dr. Mihai Mavru,
Caritas University Hospital, Bucharest, Romania.
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