Medical diagnostics benefit from polymer ball bearings

What was needed? 
Ball bearing in the unit of the rehab device located in the MRI scanner

Requirements:
Suitable for use in MRI: non-magnetic and non-conductive, bidirectional compatibility between MRI and rehabilitation device must not be disturbed; low-friction, lubrication- and maintenance-free

Industry sector
Medical technology

Success for the customer:
The non-magnetic xiros ball bearings made of plastic with glass balls are ideal for use in magnetic resonance tomographs and do not lead to any impairment of bidirectional compatibility. As they do not require any external lubrication, the bearing points remain clean, have low friction and a long service life.

The system developed at Sabancı University in Istanbul is designed to be operated during functional magnetic resonance imaging (fMRI) in order to realise physiotherapy exercises. This enables the MRI device to map the activated regions of the brain. Conclusions can be drawn from this to guide physiotherapy in such a way as to increase the effectiveness of treatment, for example for people suffering from neurological disorders following a stroke. The device is able to successfully transmit controlled forces measured by fibre optic encoders attached to compliant elements. Patients are optimally supported while ensuring their safety. This elastic force control architecture, which achieves excellent force control performance within the required frequency ranges, essentially transforms the force measurement problem into a position sensing problem. This force measurement is necessary due to the inevitable friction generated by the Bowden cables.

The most important aspect of MRI-compatible rehabilitation is the bidirectional compatibility issues between the MRI device and the rehabilitation device. Bidirectional compatibility requires that the device does not interfere with the imaging process or cause image interference and at the same time the performance of the device is not affected by the imaging process. Sabancı University's search was for non-magnetic, non-conductive plastic ball bearings that are not only maintenance-free but also durable.

The components located in the MRI area must be MRI-compatible due to the strong magnetic field. This also applies to the bearings, which should have low friction. A xirodur® B180 polymer ball bearing with glass balls is used in this area. In addition to the aforementioned requirements of non-magnetic and low friction, these bearings are lubrication and maintenance-free and have a long service life. As excessive friction has a negative impact on the transmission of assistance to the patient, the xiros plastic ball bearings ensure that the patient is optimally supported.