Planning and analyzing robotized TMS using virtual reality.

Transcranial Magnetic Stimulation (TMS) is a powerful method to examine the brain and non-invasively treat disorders of the central nervous system. Magnetic stimulation of the motor cortex results in the activation of corresponding muscle groups. Hereby, accurate placement of the TMS coil to the patient's head is crucial to successful stimulation. We developed a way to position the TMS coil using a robot and navigate it in virtual reality based on an online registration of the cranium relative to 3D magnetic resonance imaging data. By tracking the head and robotic motion compensation, fixation of the patient's head becomes obsolete. Furthermore, a novel method for motor cortex mapping is presented. The robotized TMS system is used to obtain the characteristic field of a TMS coil. This field is registered to the field of motor evoked potential measurements at the patient's head to yield a prediction of the motoric center of a target muscle.