MRI-Safe Motor Makes Robotic Biopsies Possible

A Computer can accurately control the motor that drives the devices so 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,” stated Dan Stoianovici, Ph.D., an associate professor of urology at Johns Hopkins University (Baltimore, MD, USA) and director of the Urology Robotics Laboratory. "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 completely out of plastics, ceramics, and rubber, and driven by light and air, was published in the February 2007 issue of the journal IEEE/ASME ASME [Institute of Electrical and Electronics Engineers/American Society of Mechanical Engineers] Transactions on Mechanotronics.

The obstacle for the engineers was to overcome MRI's dependence on strong magnetic interference. Metals are unsafe in MRI units because the machine relies on a strong magnet, and electric currents distort MR images, according to Dr. 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 evaluation 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,” stated Dr. Stoianovici.
The new Johns Hopkins motor, called PneuStep, consists of three pistons connected to a series of gears. The gears are turned by airflow, which is then controlled by a computer situated in a room adjacent to the MRI machine.

The robot goes alongside the patient in the MRI scanner and is controlled remotely by observing the images on the MR. The motor is equipped with fiber optics, which feeds information back to the computer in real time, allowing for both guidance and readjustment. This type of precision control will allow clinicians to utilize instruments in ways that currently are not possible.


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