Navigated and Robotized Transcranial Magnetic Stimulation based on 3D Laser Scans

Navigated and robotized Transcranial Magnetic Stimulation (TMS) is advancing forward in research and treatment. MRI-scans or other medical image data are typically used as navigation source. Unfortunately, scanning time is always short and expensive. For many TMS-applications the underlying brain topology is not necessarily needed. Therefore, we generate the subject's head contour for a precise stimulation from 3D laser scans. We use the PowerCrust algorithm generating a smooth contour from laser surface points. The mean error found was 0.289 with an RMS error of 0.358 mm and a maximum error of 0.984 mm comparing MRI-scan to laser scan for a head phantom. Currently, we are working successfully with head contours based on 3D laser scans for two ongoing TMS studies. During these TMS-experiments, the overall error found for the robotized TMS system using laser scans was < 5 mm. With new and faster laser technologies, it will be possible to use laser scans as navigation source and for direct head tracking during stimulation when scanner become real time capable.