Co-registration of stereotactic MRI and isofieldlines during deep brain stimulation.

OBJECT: The parameter adjustment process during deep brain stimulation (DBS) for dystonia remains time consuming and based on clinical observation alone. The aim was to correlate the electric field with the GPi anatomy to be able to study the stimulated volume.
METHODS: We developed a computer-assisted method (model) for visualizing electric field in reference to the stereotactic space. Electric field values were correlated with the GPi anatomy (stereotactic Magnetic Resonance Imaging) in one reference patient.
RESULTS: Using this methodology it becomes possible to correlate the electric field distributions for patient specific parameters with the anatomical information. The application to one patient showed that the 0.1V/mm isofieldline fits best with the lateral GPi borders at the level of the stimulated contacts.
CONCLUSIONS: The electric field is a crucial parameter as it is assumed to be responsible for triggering action potentials. Electric field visualisation allows the calculation of the stimulated volume for a given isoline. Its application to our whole patient population might help in determining a threshold for obtaining a therapeutic effect, to date unknown, and consequently in optimizing the parameter setting in each patient.