Researches On Head Modelingand Electric Field Of DBS With The Anisotropic Numerical Head Model

Parkinson’s disease (PD) is a type of nerve system disease. At present the deep brainstimulation (DBS) has become an effective means of treatment of Parkinson’s disease. But theunderlying mechanisms of DBS on Parkinson’s disease remain unknown. So here, this studypresents a fine head finite element model of deep brain stimulation to examine the electric fielddistribution. The electrical field distributions of DBS are analyzed based on an anisotropic realhead model and comparisons are carried out between two different medium such as isotropicand anisotropic brain models. The head model using a geometrically accurate model includesfour layers, i.e., scalp skull, CSF, brain. The purpose of this study is to evaluate the impacts ofDBS on electric distribution by incorporating brain anisotropy in a forward numerical model forDBS.Firstly, image segmentations and surface reconstruction of head orgnizations are carriedout by Simpleware software (medical image reconstruction software) based on the thoughts ofreverse engineering. Then, the surface model is transformed into physical model by using thereverse engineering Geomagic studio software, including four layers of scalp, skull, CSF(Cerebrospinal fluid) and brain.Secondly, the physical head model is imported into COMSOL software to construct thenumerical head model which is employed to the computation of electric fields by finite elementmethod (FEM). And tetrahedron elements are applied in this head mesh system. Based on deepbrain stimulation theory a bipolar electrode with two contacts was placed into the deep brainregion.Finally, in the numerical model, the electric field and potential distributions were studied.This study compares the electric distributions with bipolar stimulation between isotropic andanisotropic brain conductivity models. Further comparisons are also done between themonopolar and bipolar electrode stimulation on the brain conductivity model. The influence ofelectric field distributions through setting the electrical pulses and the effects of distances between two contracts on electric distributions is analyzed. It is found that the electricdistributions are very different on the isotropic brain model and the anisotropic brain model, sobrain anisotropy should be considered. Using monopolar electrode stimulation, we can use thesmallest stimulation parameters to get the best effect of stimulations; bipolar stimulation, thechange of electrode contact distance not only affects changes of the electrode role position, butalso changes the scope and strength of the electrical stimulation. And when electrode contactspacing is half of the electrode contact length, we can achieve good stimulation scope and effectof stimulation. At the same time, changing the stimulus pulse waveform, or changing stimulatepulse amplitude can also change the stimulus intensity and range.