Technical Data

• What was needed? Bidirectionally compatible ball bearings 
• Requirements: reduced friction, dry-running, maintenance-free
• Material: xirodur B180
• Branch of industry: medical equipment
• Success for the customer: the non-magnetic polymer ball bearings with glass balls by igus are ideal for magnetic resonance imaging and are valued due to their perfect bidirectional compatibility

The rehabilitation system of the Sabancı University in Turkey:

This system is designed as a rehabilitation device to be applied during functional magnetic resonance imaging (fMRI). MRI-compatible rehabilitation devices can be used in the strong magnetic field of MRI equipment for realising physiotherapeutic exercises. This enables the MRI device to display the activated brain regions, leading to conclusions for directing the physiotherapy in such a way that the treatment effectiveness is increased. This can result in positive effects on the quality of life of millions of people who suffer from neurological disorders, such as a stroke.  
 
The device is capable of successfully transmitting controlled forces, measured by fibre optic encoders that are attached to flexible elements. The patients are optimally supported, and at the same time, their safety is guaranteed. This architecture for elastic force control, which achieves excellent force control performance within the required frequency ranges, basically turns the problem of force measurement into a problem of position detection.  This force measurement is necessary due to the inevitable friction caused by the Bowden cables. 

Problem

The most important aspect of MRI-compatible rehabilitation is the bidirectional compatibility problems between the MRI device and the rehab equipment. To ensure bidirectional compatibility, the device must not disturb the imaging process or cause image interferences. At the same time, the performance of the device must not be affected by the imaging process. Sabancı University searched for non-magnetic, non-conductive polymer ball bearings that were not only maintenance-free but also had a long service life.

Solution

The components located in the MRI area have to be MRI compatible due to the strong magnetic field. This also applies to bearings with low friction. In this area, a xirodur B180 polymer ball bearing with glass balls is used. In addition to the mentioned requirements, and due to their non-magnetic and low-friction properties, they are lubrication and maintenance-free and have a long service life. As too high friction has negative consequences for transmitting the forces to the patient, the xiros polymer ball bearings ensure that the patient is optimally supported.