Optimization of Array Magnetic Coil Design for Functional Magnetic Stimulation Based on Improved Genetic Algorithm

The human brain can be stimulated noninvasively by strong pulses of magnetic field that induce a flow of current in the tissue, leading to the excitation of neurons. Hence, transcranial magnetic stimulation (TMS) has a wealth of applications in the research, diagnosis and therapy of the brain. The key-point in the stimulation process is to ensure that the effect of the eddy currents evoked in the brain are meeting therapeutical expectations. However, the structure and parameters of the magnetic coils (MC) have very poor relationship with the TMS ability to specifically stimulate the target tissue without activating the surrounding tissues. In this paper, a cone-shaped coil, which consists of two circular coils with a cross angle, is studied and discussed. Furthermore, an array-coil unit which consists of 7 circular coils is also analyzed using an improved adaptive genetic algorithm (IAGA) to search for the optimal parameters of the coils in order to obtain the desired deep and sharp distribution of magnetic fields in deep magnetic stimulation.