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Topic Name: MrBot : fully-actuated robot for image-guided access of the prostate gland.

Category: Robotics

Research persons: Stoianovici, Alexandru Patriciu, Doru Petrisor, Dumitru Mazilu, and Louis Kavoussi, all of Hopkins

Location: Johns Hopkins Bayview Medical Center,Mason F. Lord Building, West Tower,URobotics Laboratory, Room 115,
5200 Eastern Ave.Baltimore, MD 21224
, United States

Details

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.

The robot is customized for transperineal needle insertion and designed to be compatible with Magnetic Resonance Imagers (MRI) of the highest field strength. MrBot can accommodate various needle drivers for different percutaneous interventions such as biopsy, thermal ablations, or brachytherapy.

For MRI compatibility the robot is exclusively constructed of nonmagnetic and dielectric materials such as plastics, ceramics, and rubbers and is electricity free. The system utilizes a new type of motor specifically designed for this application, the pneumatic step motor. This unique motor design provides easily controllable, precise, and safe pneumatic actuation. Light based encoding is used for feedback, so that all electric components are distally located outside the imager’s room.

Motion tests showed very fine performance with fraction of millimeter accuracy. Imager compatibility tests performed in scanners up to 7 Tesla showed outstanding MRI compatibility, independent of the field strength. MRI-guided needle targeting experiments showed that the tip of the needle may be placed within 1mm of a desired target selected in the image. Cadaver and animal tests are in progress. Partial results are very promising.

“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.
 

Research Persons:

Dan Stoianovici, Ph. D.

Associate Professor of Urology and Mechanical Engineering
Johns Hopkins University

Director, Urology Robotics Program
Johns Hopkins Medicine


Email:dss@jhu.edu

Alex Patriciu PhD
PhD Student
1999-2004
Post Doc Fellow
2004-2006
Presently
Assistant Professor
McMaster University
Canada

Doru Petrisor PhD
Mathematician
Engineer

Dumitru Mazilu PhD
Research Associate
1999-2006
Presently at the NIH

Louis Kavoussi MD
Founder and Coordinator
1996-2005
Presently
Professor and Chair, Urology
LIJ Health System, NY
 

Funded:

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.