MRI-Safe Robot Can Take Guided Biopsies During Imaging

Most robotic motors are electromagnetic--so they are excluded from the MRI chamber. If you want an MRI-guided robot to work on a patient during the MRI procedure, you have to try a different type of motor. The pneumatic stepper motor--controlled by optical fibre--is an obvious fit.

“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.

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Such electricity-free motors should be useful in other areas where the absence of magnetism and electricity are important.

I am not thrilled at the prospect of a pneumo-robot creeping around my nether regions, snipping and stabbing--particularly within the confines of a mega-magnetic tube. Fortunately, by the time I am ready for such things, robots will be nano-sized and MRI will by superseded by gentler imaging techniques.

Hat tip medgadget