During TMS treatment, the patient sits on a chair and a treatment coil is applied to their head. A TMS machine passes an electric current through the magnetic coil to generate a magnetic field, typically around two Tesla — a similar strength to an MRI scanner. This magnetic field is used to either stimulate or inhibit neurons in the cerebral cortex, the outer layer of the brain.
Exact locations and frequencies used for treatment vary depending on the condition being treated. When used for depression, the coil is placed over areas in the brain responsible for emotional control. For patients diagnosed with depression, these areas are often ‘underactive’ — by stimulating the neurons, this part of the brain can be reactivated, alleviating the negative symptoms experienced by the patient.
to the success of TMS treatment is the precision of the coil positioning. A course of TMS treatment typically comprises of one session daily, over a period of four to six weeks. Repetition is key in achieving the best possible patient outcome, but to do this, the machine must be able to accurately position itself each time.
Such accurate positioning is difficult to achieve manually. As a result, robotic arms have been developed to precisely position the coil, based on previous scans and measurements of the patient’s head. An optical monitoring system can be used to detect any head movements made throughout the treatment and allow the TMS machine to compensate accordingly.
Motors used within these robotic arms must meet stringent requirements. For those motors closest to the coil, high electromagnetic compatibility (EMC) immunity is required. This is due to the strength of the magnetic field emitted, and to minimise any interference caused by the equipment.
A high starting torque is desirable for the machine to adjust quickly to sudden head movements. With the repeated nature of TMS treatments, it’s likely that the machine will be running for extended periods every day. As a result, the motors must also be able to work reliably, and without overheating or any loss of precision.
Finding micromotors capable of meeting such requirements while being compliant to medical regulations can be a challenge. FAULHABER motors, supplied in the UK and Ireland by EMS, have already been trialled and successfully implemented in a variety of medical applications, including TMS machines.