Abstract
Background: Current approaches to detect the positions and orientations of directional deep brain stimulation (DBS) electrodes rely on radiative imaging data. In this study, we aim to present an improved version of a radiation-free method for magnetic detection of the position and the orientation (MaDoPO) of directional electrodes based on a series of magnetoencephalography (MEG) measurements and a possible future solution for optimized results using emerging on-scalp MEG systems. Methods: A directional DBS system was positioned into a realistic head–torso phantom and placed in the MEG scanner. A total of 24 measurements of 180 s each were performed with different predefined electrode configurations. Finite element modeling and model fitting were used to determine the position and orientation of the electrode in the phantom. Related measurements were fitted simultaneously, constraining solutions to the a priori known geometry of the electrode. Results were compared with the results of the high-quality CT imaging of the phantom. Results: The accuracy in electrode localization and orientation detection depended on the number of combined measurements. The localization error was minimized to 2.02 mm by considering six measurements with different non-directional bipolar electrode configurations. Another six measurements with directional bipolar stimulations minimized the orientation error to 4°. These values are mainly limited due to the spatial resolution of the MEG. Moreover, accuracies were investigated as a function of measurement time, number of sensors, and measurement direction of the sensors in order to define an optimized MEG device for this application. Conclusion: Although MEG introduces inaccuracies in the detection of the position and orientation of the electrode, these can be accepted when evaluating the benefits of a radiation-free method. Inaccuracies can be further reduced by the use of on-scalp MEG sensor arrays, which may find their way into clinics in the foreseeable future.
Highlights
Introduction distributed under the terms andDeep brain stimulation (DBS) is a neurosurgical procedure in which electrodes are placed within the brain to electrically stimulate specific target areas, thereby modulating dysregulated neural circuits [1]
In previous papers [18,19], we have demonstrated that this dipole model, which applies to an infinite homogeneous space and neglects the modeling of the volume conduction, describes a good approximation for the bipolar electrode configuration depicted in Figure 5 within realistic distances between electrode and MEG sensors
Since this was a rough estimate, a cuboid of 30 mm length was placed around the localized grid point that defined the region of interest (ROI) for the following precise post-localization of the electrode
Summary
Deep brain stimulation (DBS) is a neurosurgical procedure in which electrodes are placed within the brain to electrically stimulate specific target areas, thereby modulating dysregulated neural circuits [1]. Due to the relative safety, therapeutic efficacy, and postsurgically modifiable nature of DBS, it has become a common surgical procedure over conditions of the Creative Commons. While DBS is most commonly used to treat movement disorders, such as Parkinson’s disease and essential tremor, it is increasingly being investigated for its therapeutic potential regarding a range of other brain diseases, including conditions such as neuropathic pain and epilepsy. Estimating the volume of tissue activated (VTA) has demonstrated clinical advantages in programming efficacy [4] and provides a method for optimizing stimulation while avoiding side effects.
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