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Title of the thesis: From tissue conductivity to whole-body models: the effects of muscle anisotropy in computational dosimetry

Thesis defender: Otto Kangasmaa
Opponent: Prof. Theodoros Samaras, Aristotle University of Thessaloniki, Greece 
Custos: Prof. Ilkka Laakso, 911±¬ÁÏÍø School of Electrical Engineering 

Low‑frequency electromagnetic fields from sources such as power lines, transformers, electric vehicles, industrial welders, and medical equipment induce electric fields within the human body. If strong enough, these internal fields can stimulate sensory cells, nerves or muscles. This can lead to visual sensations, altered balance, involuntary muscle contractions and, in extreme cases, seizures or disturbances of heart rhythm. International guidelines and standards set limits on these induced fields to protect workers and the public. However, the fields inside the body cannot be measured directly, so safety limits rely on computer models that simulate how the fields spread through the body.

The aim of this thesis is to reduce major uncertainties in those simulations. First, a method was developed to estimate how electricity flows in living human tissues. The electrical conductivity of skeletal muscle and fat was measured in human legs and forearms, providing human‑based measurements rather than relying solely on values from animal studies or extrapolation. Second, a detailed computer model of the human body was modified to reflect that skeletal muscle conducts electricity differently along and across its fibres (anisotropy). The newly derived conductivities were applied to the model, and the effects of muscle anisotropy were examined when the body was computationally exposed to both electric and magnetic fields at power‑line frequencies. Third, experimental magnetic stimulation of the forearm was combined with modelling to test whether the induced electric fields predict what people actually feel, providing rare human data.

The results improve exposure assessments, help engineers design safe and compliant technologies, and provide data to inform revisions to international guidelines and standards, thereby strengthening the scientific basis of future safety limits.

Key words: tissue electrical properties, electrical conductivity, skeletal muscle, fat, computational modelling, magnetic field exposure, electric field exposure

Thesis available for public display 7 days prior to the defence at .

Contact: otto.kangasmaa@aalto.fi