Hamed SADJEDI, Seyyed Mohammad FIROOZABADI POURMIR, Raheleh TAVAKOLI

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.

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[1] Auvichayapat P, Auvichayapat N. Basic knowledge of transcranial direct current stimulation. J Med Assoc Thai 2011; 94: 518527.
[2] Rossi S, Hallett M, Rossini PM, Pascual-Leone A. Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research. Clin Neurophysiol 2009; 120: 20082039.
[3] Cruetzfeldt OD, Fromm GH, Kapp H. Influence of transcortical dc currents on cortical neuronal activity. Exp Neurol 1962; 5: 436452.
[4] Nitsche MA, Liebetanz D, Antal A, Lang N, Tergau F, Paulus W. Modulation of cortical excitability by weak direct current stimulation technical, safety and functional aspect. Suppl Clin Neurophysiol 2003; 56: 255276.
[5] Nitsche MA, Liebetanz D, Lang N, Antal A, Tergau F, Paulus W. Safety criteria for transcranial direct current stimulation (tDCS) in humans. Clin Neurphysiol 2003; 114: 22202222.
[6] Nitsche MA, Paulus W. Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation. J Physiol 2000; 527: 633639.
[7] Salinas FS, Lancaster JL, Fox PT. Detailed 3D models of the induced electric field of transcranial magnetic stimulation coils. Phys Med Biol 2007; 52: 28792892.
[8] Miranda PC, Lomarev M, Hallet M. Modeling the current distribution during transcranial direct current stimulation. Clin Neurophysiol 2006; 117: 16231629.
[9] Nitsche MA, Cohen LG, Wassermann EM, Priori A, Lang N, Antal A, Paulus W, Hummel F, Boggio PS, Fregni F et al. Transcranial direct current stimulation: state of the art 2008. Brain Stimul 2008; 1: 206223.
[10] Im CH, Jung HH, Choi JD, Lee SY, Jung KY. Determination of optimal electrode positions for transcranial direct current stimulation (tDCS). Phys Med Biol 2008; 53: N219N225.
[11] Park JH, Hong SB, Kim DW, Suh M, Im CH. A novel array-type transcranial direct current stimulation (tDCS) system for accurate focusing on targeted brain areas. IEEE T Magn 2011; 47: 882885.
[12] Dmochowski JP, Datta A, Bikson M, Su Y, Parra LC. Optimized multi-electrode stimulation increases focality and intensity at target. J Neural Eng 2011; 8: 129.
[13] Dmochowski JP, Datta A, Bikson M, Su Y, Parra LC. A multiple electrode scheme for optimal non-invasive electrical stimulation. In: IEEE EMBS Conference; 2011; Cancun, Mexico. New York, NY, USA: IEEE. pp. 2935.
[14] Elwassif MM, Kong Q, Vasquez M, Bikson M. Bio-heat transfer model of deep brain stimulation-induced temperature changes. J Neural Eng 2006; 3: 306315.
[15] Rush S, Driscoll D. Current distribution in the brain from surface electrodes. Anesth Analg 1968; 47: 717723.
[16] Bertsimas D, Tsitsiklis J. Simulated annealing. Stat Sci 1993; 8: 1015.
[17] Olasfsson S. Metaheuristics. Handbooks in Operations Research and Management Science, Vol. 7. Amsterdam, the ´ Netherlands: Elsevier, 2006.
[18] Kirkpatrick S, Gelatt CD, Vecchi MP. Optimization by simulated annealing. Science 1983; 220: 671680.
[19] Mendon¸ca PRS, Caloba LPN. New simulated annealing algorithms. In: IEEE International Symposium on Circuits and Systems; 912 June 1997; Hong Kong. New York, NY, USA: IEEE. pp. 16681671.
[20] Jianlan G, Yuqiang C, Xuanzi H. Implementation and improvement of simulated annealing algorithm in neural net. In: International Conference on Computational Intelligence and Security; 1114 December 2010; Nanning, China. New York, NY, USA: IEEE. pp. 519522.
[21] Wagner TA, Zahn M, Grodzinsky AJ, Pascual-Leone A. Three-dimensional head model simulation of transcranial magnetic stimulation. IEEE T Bio-Med Eng 2004; 51: 15861598.
[22] Wagner T, Fregni F, Fecteau S, Grodzinsky A, Zahn M, Pascual-Leone A. Transcranial direct current stimulation: a computer-based human model study. Neuroimage 2007; 35: 11131124.
[23] Brunoni AR, Nitsche MA, Bolognini N, Bikson M, Wagner T, Merabet L, Edwards DJ, Valero-Cabre A, Rotenberg A, Pascual-Leone A et al. Clinical research with transcranial direct current stimulation (tDCS): challenges and future directions. Brain Stimul 2012; 5: 175195.
[24] Faria P, Leal A, Miranda PC. Comparing different electrode configurations using the 10-10 international system in tDCS: a finite element model analysis. In: IEEE EMBS Conference; 2009; Minneapolis, MN, USA. New York, NY, USA: IEEE. pp. 15961599.