An application of simulated annealing to optimal transcranial direct current stimulation of the human brain

Transcranial direct current stimulation (tDCS) is known as the most effective technique for stimulating deeper brain areas. The capability of tDCS, however, strongly depends on the number of electrodes, their positions, and the amount of injected currents. This paper intends to apply the simulated annealing algorithm for determining optimal stimulation parameters in a multiple electrode scheme. The objective of the presented approach is to maximize the current density delivered to the target area under safety constraints. In order for the skin under the electrodes to be protected against temperature rises that may be caused by the stimulation, current injections are capped by a set of safety constraints. In the studies, the propagation of current density throughout the head is estimated via a 3D finite element approach in the ANSYS software package. Finally, the proposed algorithm is applied to a standard spherical four-layer human head model. The simulation results justify the capability of the established model in providing near optimal stimulation parameters. Accordingly, the presented approach provides neurologists with an effective tool to optimally stimulate the brains of patients.