gain ultrasonic vision
Technology Research News
Surgeons often use ultrasound to see where
they're going as they poke around their patients' insides with needles
and tubes during surgery.
The problem is they have to shift their attention between the patient
and the ultrasound monitor, making it difficult to coordinate what their
eyes are seeing with what their hands are doing.
Researchers from University of Pittsburgh and Carnegie Mellon University
have developed a device that overlaps the two views, giving surgeons the
illusion of peering directly into their patients' bodies.
"We aim to provide a natural, unified environment for hand-eye coordination
during invasive procedures guided by tomographic images," said George
Stetten, an assistant professor of bioengineering at the University of
Pittsburgh and a research scientist at the Robotics Institute at Carnegie
The handheld real-time tomographic reflection device, or Sonic Flashlight,
keeps the ultrasound image aligned with the patient even when the surgeon
shifts her point of view. "The Sonic Flashlight uses a flat-panel monitor
and a half-silvered mirror to produce a virtual image of the ultrasound
slice at its actual location within the body," said Stetten.
The device has three components: an ultrasound monitor, a half-silvered
mirror, which reflects a portion of the light that hits it and lets the
remainder pass through, and an ultrasound transducer, which generates
the sound waves and records their reflections. The device looks like a
rectangular box with a pistol grip at one end and a windshield -- the
half silvered mirror -- on top of the box. A small monitor is also mounted
on top of the box at an angle to the mirror. The mirror and monitor form
a V-shape when viewed from the side.
The surgeon presses the transducer against the patient's body and looks
through the half-silvered mirror at the patient while the ultrasound monitor
projects a view of the patient's insides onto the mirror. The real and
virtual views line up because each point on the ultrasound display and
its corresponding point in the patient are on opposite sides of the mirror
at precisely the same angle, said Stetten.
The key to keeping the views aligned is that the device's components are
fixed to each other so moving the transducer also changes the position
of the ultrasound monitor and half-silvered mirror. This keeps the image
of the sound waves and the parts of the patient they are depicting at
the correct angles on opposite sides of the mirror.
Other approaches to merging virtual and real views of patients use head-mounted
displays and tracking devices to keep the views aligned, but these can
be cumbersome and have limited fields of view.
"Although there have been other systems to register medical image data
with the surgeon's perspective, nice aspects of this approach include
the real-time registration and the optical illusion of the image appearing
beneath the skin," said T. Douglas Mast, an assistant professor of acoustics
at Pennsylvania State University.
The device needs to be carefully calibrated and tested before it can be
considered for surgical use, said Mast. "That calibration will actually
be extremely difficult, since the inhomogenous sound speed in the body
must be accounted for. This is a big impediment toward surgical use, since
surgeons need very accurate indications of where their [instruments] are
going," he said.
It is likely to take between two and five years before practical applications
are possible, said Stetten.
Stetten's research colleagues were Vikram Chib, Daniel Hildebrand and
Jeanette Bursee of the University of Pittsburgh. They presented the research
at the IEEE/ACM International Symposium on Augmented Reality in New York
in October. The research was funded by the Whitaker Foundation and Carnegie
Timeline: 2-5 years
Funding: Private; University
TRN Categories: Data Representation and Simulation; Applied
Story Type: News
Related Elements: Technical paper, "Real Time Tomographic
Reflection: Phantoms for Calibration and Biopsy," IEEE/ACM International
Symposium on Augmented Reality, New York, October, 2001
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