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Baltimore, MD, 6 April 2007: Engineers at
the Johns Hopkins Urology Robotics Lab report the invention of a motor without
metal or electricity that can safely power remote-controlled robotic medical
devices used for cancer biopsies and therapies guided by magnetic resonance
imaging. The motor that drives the devices can be so precisely controlled by
computer that movements are steadier and more precise than a human hand.
“Lots of biopsies on
organs such as the prostate are currently performed blind because the tumors are
typically invisible to the imaging tools commonly used,” says Dan Stoianovici,
Ph.D., an associate professor of urology at Johns Hopkins and director of the
robotics lab. “Our new MRI-safe motor and robot can target the tumors. This
should increase accuracy in locating and collecting tissue samples, reduce
diagnostic errors and also improve therapy.”
A description of the new
motor, made entirely out of plastics, ceramics and rubber, and driven by light
and air, was published in the February issue of the IEEE/ASME Transactions
on Mechanotronics.
The challenge for his
engineering team was to overcome MRI’s dependence on strong magnetic
interference. Metals are unsafe in MRIs because the machine relies on a strong
magnet, and electric currents distort MR images, says Stoianovici. The team used
six of the motors to power the first-ever MRI-compatible robot to access the
prostate gland. The robot currently is undergoing preclinical testing.
“Prostate cancer is
tricky because it only can be seen under MRI, and in early stages it can be
quite small and easy to miss,” says Stoianovici.
The new Johns Hopkins
motor, dubbed PneuStep, consists of three pistons connected to a series of
gears. The gears are turned by air flow, which is in turn controlled by a
computer located in a room adjacent to the MRI machine. “We’re able to achieve
precise and smooth motion of the motor as fine as 50 micrometers, finer than a
human hair,” says Stoianovici.
The robot goes alongside
the patient in the MRI scanner and is controlled remotely by observing the
images on the MR. The motor is rigged with fiber optics, which feeds information
back to the computer in real time, allowing for both guidance and readjustment.
“The robot moves slowly
but precisely, and our experiments show that the needle always comes within a
millimeter of the target,” says Stoianovici. This type of precision control will
allow physicians to use instruments in ways that currently are not possible, he
says.
“This remarkable robot
has a lot of promise - the wave of the future is image-guided surgery to better
target, diagnose and treat cancers with minimally invasive techniques,” says
Li-Ming Su, M.D., an associate professor of urology and director of laparoscopic
and robotic urologic surgery at the Brady Urological Institute at Hopkins.
The research was funded by the National Institutes of Health, the Prostate
Cancer Foundation, and a grant from the Johns Hopkins Medicine Alliance for
Science and Technology Development Industry Committee. Current experiments with
the robot are supported by the Patrick C. Walsh Foundation.
Authors on the paper are
Stoianovici, Alexandru Patriciu, Doru Petrisor, Dumitru Mazilu, and Louis
Kavoussi, all of Hopkins.
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