Micronor Claims Complete Operational Transparency for MRI Rotary Encoder

A new encoder is the world's first and only commercially available nonmetallic rotary position sensor that can operate with complete "transparency" in extreme electromagnetic fields, according to its manufacturer, Micronor Inc. (Newbury Park, CA). The MR318 MRI-compatible fiber-optic rotary encoder can function both as an incremental and absolute position encoder, enabling motion control apparatuses used in functional-MRI (fMRI) R&D of advanced MRI phantoms.

Enabling medical personnel to monitor the brain activity of impaired patients while they are engaged in various locomotor activities such as pedaling, lifting, and limb movement, the device allows medical researchers and radiologists to develop an MRI-compatible test and diagnostic apparatus in which measuring position, angle, or speed is required. For example, monitoring brain activity at discrete pedal positions allows researchers to observe how the brain and body adjust to therapy and evaluate new rehabilitation techniques. The encoder also enables the development of more-sophisticated MRI phantoms for machine calibration, teaching, and training purposes.

Prior to the MR318, engineers had no commercial solution for measuring continuous position within an MRI chamber. Motors or actuators could be hydraulic or pneumatic, but no commercial, nonmetallic position sensor existed. A homemade fiber-optic proximity/limit switch was the best solution, but this awkward-to-design package could only provide position information at discrete points. The advent of the MR318 enables a fully functional motion control apparatus with closed-loop feedback, says Dennis Horwitz, Micronor's vice president of sales and marketing.

The encoder combines Micronor's passive fiber-optic encoder technology with material engineering that flows down to the smallest component. For interchangeability and compatibility with existing products, the encoder uses the industry-standard 58-mm form factor and pairs with the MR310 interface module.

The product concept grew out of requests for a nonmetallic version of the company's existing fiber-optic encoder products. The first application for the prototype MRI encoder, a pedaling device, was provided by Jay Mehta, a graduate student in the biomedical engineering department at Marquette University (Milwaukee), and his advisor, Sheila Schindler-Ivens. The results of their research project were published in the Journal of Neuroscience Methods in May 2009 under the title, "A Novel Technique for Examining Human Brain Activity Associated with Pedaling Using fMRI."