DTI-based Calculation Of White Matter Conductivity And Numerical Simulation Study Of Brain Stimulation

With the developing technology of diffusion tensor imaging(DTI) technology, it is become more promising about getting the conductivity of the brain by non-invasive way and tracking white matter fiber bundle. The conductivity of brain tissue with strong anisotropy and how to get it always be a key point for many researchers. The Parkinson’s disease and mental disorders of these medical problems, hope to find more superior treatments instead of causing necessary harm transcranial direct current stimulation(t DCS) achieve the above requirements completely. It attractive people’s attention gradually, because its superiority as security and economy. The main contents of this thesis include the following two aspects.Firstly, due to the importance of the conductivity parameters, analyzed the mathematical model which is calculated conductivity by the method of diffusion tensor, include linear relationship model, the volume constraint model and electrochemical models. Through introduced a structural coefficient, the thesis deduced the relationship between the diffusion coefficient and the tissue conductivity from the perspective of electrochemical and echo response equivalent and provided a reference for the calculation of electrical conductivity. Based on the DTI data of actual measurement, the different calculation models of calculating conductivity were comparative studied, there were great discrepancies existed in those computational models. The results revealed linear relationship model was reliable relatively.Second, study on simulation of the field distribution in the sphere head model. In order to simplify analyze problem, based on conductivity of homogeneous tissue, A three layers sphere model was used as the head model. The t DCS numerical simulation was achieved through programming. The effect of the injection current for different electrode size was studied in the four layers sphere model. The results found the smaller electrode was stronger on the skull penetration ability and the injected current was decreased obviously when it through the skull. By analyzed the influence of cerebrospinal fluid to field distribution, we concluded the cerebrospinal fluid greater impacted to the distribution of current density. Therefore, choose the appropriate calculation model to solve different problems. The multi electrode focus question of t DCS was calculated with the intelligent algorithm. Stimulus focus was achieved through the simulation calculation results. The results of the study will provide a reference for further study of electric stimulate focus in the real head model.