3D rendering in NeNa software of subject brain with activation map. 3D cursur spheres are used to indicate facial marker points.

Transcranial Magnetic Stimulation (TMS)

In the neurosciences and clinical praxis, the use of TMS is rapidly increasing. When using TMS, brain activity in healthy volunteers and patients can be safely and reversibly altered for a short time period. It adopts a focussed magnetic field deployed by a coil held over the head, which penetrates the skull unattenuated. This magnetic field change then causes an electric field in the brain, which can induce finger movements, prevent speach or memory retrieval depending on the brain area that is stimulated.

A subject in the lab during navigation with NeNa

Neural Navigation for TMS

The use of TMS requires accurate placement of the coil over a brain region of interest with an accuracy up to a few millimeters. No two brains are alike, therefore the placement of the TMS coil based on head shape alone is unsufficient. An increasing number of researchers wants to use individual MRI scans, possibly with added functional imaging maps, to accurately guide the TMS coil to it’s goal. To do this, the spatial registration of the head of a research participant with the MRI scan is crucial. The solution of this problem is referred to as ‘neural navigation’ or 'neuronavigation'. Added to that, a neural navigator would display the position of a handheld pointer with respect to a 3D representation of the participant’s head and brain on a computer screen in 3D.

Real time homing in on cortical surface in birds-eye view (as if viewed from hand-held pointer) in NeNa version 1.5.

A new neural navigator: NeNa

Our neural navigator is especially tailored to offer the functionality as mentioned above for the use with TMS. It is accurate and easy to use, and offers exactly what a researcher needs without unnecessary bells and whistles. It accepts data formats and analysis results as produced by SPM and other major fMRI analyses packages. NeNa adopts a proven registration technology, which is not secret but published in detail in a respected international scientific journal*. Furthermore, it is rigourously tested on a number of participants and using computer simulations, which is published in the same paper. It uses the DriveBAY, a commonly available and affordable 3D digitizing device.

Reference

Neggers SF, Langerak TR, Schutter DJ, Mandl RC, Ramsey NF, Lemmens PJ, Postma A. A stereotactic method for image-guided transcranial magnetic stimulation validated with fMRI and motor-evoked potentials. Neuroimage 21:1805-1817, 2004.