School of
Information Technology and Electrical Engineering

Speaker: Rawan Abu Yosef
Seminar Date: Fri, 23/02/2018 - 11:30
Venue: 49-502; AEB Seminar Room
Host: Prof Amin Abbosh

Seminar Type:  MPhil Confirmation Seminar


Transcranial Magnetic Stimulation (TMS) is a neurophysiological technique that can be used as a non-invasive tool for many neurological conditions. In TMS, a time-varying magnetic field generated from an electromagnetic coil placed on the scalp induces an electric field inside the brain. TMS coil geometry plays a vital role in determining the focality and depth of penetration of the induced electric field responsible for the stimulation process. Clinicians and brain scientists are interested in stimulating a localized area of the brain, while minimizing the stimulation of surrounding neural networks. For TMS, focality and depth of penetration are inversely proportional, and this trade-off is hard to beat due to the rapid decay of the magnetic field with respect to distance from the coil.

In this study, the band of frequencies that might be suitable for TMS in brain stimulation and therapy are investigated. Moreover, a novel highly-focal TMS coil is designed to stimulate deep region in the brain for treating progressive neurodegenerative diseases, while abiding the safety consideration in terms of field's absorption and temperature variation. The simulations of the electromagnetic field induced in the brain by the TMS coils are done using the Sim4life software (Sim4life, ZMT Zurich MedTech AG). In Sim4life a low-frequency magneto quasistatic finite element method (FEM) solver is used to obtain the field distribution. To create a realistic simulation environment, a three-dimensional high-resolution head model, named MIDA is utilised in this study. The model is imported as a computer-aided design (CAD) object, and different tissues are defined according to their frequency-dispersive dielectric properties, so that the change of frequencies represents the varied realistic dielectric properties of the tissues.

This project addresses frequency variation effect on the induced electric and magnetic fields, through electromagnetic simulations. A coil is designed and applied on a realistic human head model at different frequencies and excitation currents. It is observed that to choose the optimum frequency range for the TMS coil, several factors including, the safety limits, stimulation threshold, desired magnetic flux density, and the target depth need to be considered. It is also found that low frequencies offer higher magnetic flux density and lower electric field threshold value for stimulation, while high frequencies allow reducing the excitation current of the TMS coil. On the other hand, the depth of the stimulus and focality of the field do not change with frequency variation. Additionally, the impact of adding an iron core and shielding to the TMS coil is studied. A noticeable improvement in the magnetic and electric field is reported using these modifications.


Rawan Abu Yosef received her Bachelor Degree from Birzeit University, Palestine in 2008. She joined the team of Palestine Polytechnic University in the same year as a lecturer and projects supervisor in the College of Applied Professions until she moved to Australia, late in 2015. She is currently an MPhil candidate in the School of Information Technology and Electrical Engineering at The University of Queensland. Her research interests include electromagnetics for brain stimulation and other biomedical applications.