Soterix Medical High-Definition transcranial Electrical Stimulation (HD-tES) is a non-invasive technique where desired brain regions are targeted using arrays of scalp electrodes. Soterix Medical neurotargeting software HD-Targets leverages mathematical optimization to automatically determine the best HD electrode configuration for any target. For patient-specific optimization, localizing the HD sites onto the patients’ scalp based on patient’s MRI ensures precise electrode placement. This as a result ensures precise and consistent HD-tES application.
Perform HD-tES Neuronavigation in three easy steps:
1) Use HD-Targets to determine optimal electrode placement for your brain target.
2) Load stimulation electrode voxel locations into Neural navigator software.
3) Navigate to stimulation electrode location using individual's MRI and mark location on scalp.
Most navigation systems use either optical (infrared) or electromagnetic tracking technology. Both systems perform the same function- however, the technology used to provide information to the operator is substantially different. The optical system uses infrared sensors in combination with light emitting structures that are fixed to the subject’s head via a headband and fixed to a hand-held probe. Both the headband and the instrument must be “seen” by the system’s camera in order to allow navigation. Optical systems are typically more expensive. The electromagnetic systems like the Neural Navigator on the other hand use electromagnetic fields that use reference points on a device attached to the patient’s head (held via headband). Unlike the optical systems, electromagnetic systems do not have to be “seen” by a camera and therefore do not suffer from line of sight occlusion (LOS) issues. In fact, electromagnetic tracking dominates the surgical navigation field due to no LOS issues. Furthermore, the Neural Navigator system uses DC pulsed tracking enabling it to match the precision and accuracy of optical systems.
The net result therefore is a fundamental advance in Neuronavigation – a system that matches the precision and accuracy of optical systems while not being affected by LOS occlusion and is more affordable.
During neuronavigation, the 3D positions and angles of the TMS coil, a digitizing stylus and the head of the patient typically must be known at all times. Position tracking of coil, head and stylus can be performed either using optical position tracking with large cameras on a stand, or electromagnetic (EM) position tracking based on a DC pulsed magnetic field emitted by a small box. In Neurosurgery, where the principle of frameless stereotactic neuronavigation was invented decades ago, both optical and EM tracking techniques have been around for a long time, and have proven their worth. They are found to be equally accurate in larger studies ( Koivukangas 2013 & Ricci 2008). Especially EM tracking offers several advantages, and is currently popular in neurosurgical navigation applications requiring high precision and reliability. The main advantage of EM tracking remains immunity to line-of-sight occlusion, or avoiding the inability to track and navigate when the camera view is blocked, for example by the arms of a person using the equipment. However, another important advantage is the compact nature of EM tracking, no big camera stand is needed, and sensors are much smaller as well. The DC pulsed EM navigation that neurosurgeons use often, and is also used in the Neural Navigator, is very robust, as it does not induce so called ‘Eddy currents’ in metals that otherwise would cause distortions. The material used inside a TMS coil also does not pose any problem for EM position tracking based on DC pulses. The Neural Navigator was originally developed and rigorously tested at Utrecht University Medical Center in the Netherlands currently has numerous users around the globe – some of which have been successfully using the system since 2011. Of course a magnetic pulse generated by a TMS coil very briefly interferes with EM position tracking nearby the TMS coil, for about 1 millisecond. This brief distortion is detected in real-time and removed by the Neural Navigator proprietary and fully validated algorithms. This allows seamless position tracking of coil and head even during high frequency rTMS and even theta burst TMS protocols.
No two brains are alike, making precision placement of the coils used in TMS Therapy tricky. Precise and reliable positioning can make the difference between a successful result and an unsatisfactory one. Conventional coil placement is done using anatomical landmarks like the bridge of the nose, the projecting part of the back of the skull, etc. to align the coil over an intended brain target. This is called the “non-navigated approach." This approach does not need the patient’s MRI.
The “navigated approach”, on the other hand, uses the patient’s MRI, thereby taking into account the individual’s anatomy. From the MRI, one marks out desired brain targets using individual brain landmarks (gyri and sulci). Once marked, the coil can be positioned to within a mm precision over the target. Any subject or operator movement can be immediately compensated for- as the brain target is always visible. This approach is similar to the one taken in image-guided stereotaxy when performing brain surgery. Studies have shown unequivocally greater benefit (up to twice as much) when using a navigated approach over the non-navigated one for TMS treatment.
Figure on left from "A randomized trial of rTMS targeted with MRI based neuro-navigation in treatment-resistant depression” Fitzgerald PB, Hoy K, McQueen S, et al. Neuropsychopharmacology 2009.
‘Standard‘ indicates Non-Navigated approach
‘Targeted‘ indicates Navigated approach
Koivukangas T, Katisko JP, Koivukangas JP. Technical accuracy of optical and the electromagnetic tracking systems Springerplus. 2013 Mar 8;2(1):90 Ricci WM, Russell TA, Kahler DM, Terrill-Grisoni L, Culley P. A comparison of optical and electromagnetic computer-assisted navigation systems for fluoroscopic targeting. J Orthop Trauma. 2008 Mar;22(3):190-4.
Upon request, Soterix Medical support team can provide assistance and advice in MR image processing and MRI data quality inspection.
Neural Navigator by Brain Science Tools BV is exclusively distributed in the US and Canada by Soterix Medical. Neural Navigator has extensive regulatory agency approvals worldwide: European Union (CE), Canada (Health Canada), and Brazil (ANVISA)