Human head temperature and electric field investigations under ECT

Human head temperature and electric field investigations under ECT

Electroconvulsive therapy (ECT) is a non-invasive technique used to treat psychiatric conditions. A high strength low frequency electrical stimulation is delivered through two electrodes. The aim of this work is to develop an ECT finite element human head model to investigate the electric field and the increase in temperature due to the electrical stimulation.

The bio-heat transfer equation combined with Laplace equation and their initial and boundary conditions are used to define the physics of the models. Firstly, finite ele-ment spherical human head models are created in COMSOL Multiphysics and the behaviour of the thermal field due to ECT electrical stimulation is analysed. Hetero-geneity was considered and thermal anisotropy of the skull layer was applied to the finite element models.

Secondly, a realistic human head model is created using magnetic resonance images (MRI). Similar physics is applied to define the thermal and electrical problems, and the anisotropic conductivity of the skull is considered. The realistic models contain anatomical features and realistic tissue conductive properties. Through these models we investigate the role of stimulation parameters such as: electrode montages, strength of stimulation, temperature behaviour, etc. Later on, another realistic human head model with a brain tumor is created and a diffusion tensor image is included. Based on this model the white matter anisotropy is considered and the effect on the electric field is analysed.

The results show that high temperatures only occur on external areas of the head, such as scalp and fat. The thermal conductivity anisotropy is insignificant from a heat-transferring point of view. However, the electrical anisotropy does need to be included in order to get more accurate outcomes. If ECT was applied to a patient
with a brain tumor, then factors such as tumor location, aggressiveness, electrode montage, etc would need to be considered. Further work can be undertaken through computational simulation to make personal ECT treatment feasible in clinical practice.