Deterministic-Stochastic Methods in Electromagnetic Thermal Dosimetry for the Assessment of Human Exposure to Electromagnetic Fields in GHz Range

Dragan Poljak, PhD

University of Split, FESB, Split, Croatia

Although deterministic numerical techniques provide a satisfactory insight into bioelectromagnetics
phenomena in GHz range, there are still some issues that cannot be addressed efficiently by using
deterministic modeling only. The biological tissues are represented by electrical properties;
permittivity, conductivity and permeability. However, the exact value of these parameters is not
known, as their values may vary due to frequency, gender, age, or health of a person, respectively.
Most of these parameters are obtained under different measurement on ex vivo animal and human
tissues, and exhibit large variations from their averages. When used in computational models, these
average values lead to rough approximation of the realistic scenarios.
The uncertainty from the input is, hence, inevitably propagated to the output of interest such as;
induced field, specific absorption rate (SAR) or absorbed power density (Sab).
These problems could be somewhat overcome by a combination of deterministic models with
stochastic methods. Therefore, the uncertainty quantification (UQ) deals with the uncertainties in
the model response, due to the input parameters being random variables, while sensitivity analysis
(SA) provides the information on the impact of the mutual interactions between the input variables
to the output value of interest. Usual UQ methods rely upon statistical approaches, such as Monte
Carlo (MC) simulations, being easy to implement but the sample size needs to be very high
(>100.000), resulting in a slow convergence rate. This drawback could be overcome by using
sophisticated stochastic modeling.
Tutorial first covers deterministic approaches in electromagnetic-thermal dosimetry with particular
emphasis to exposures in GHz frequency range mostly pertaining to 5G systems. The use of integral
equation approaches featuring Method of Moments(MoM) and Boundary Element Methods (BEM),
and differential equation approaches such as Finite Element Methods (FEM) is addressed. Some
strengths and weaknesses of both approaches are discussed throughout Tutorial as well.
Tutorial then deals with stochastic procedures in electromagnetic-thermal dosimetry in lower
portion of GHz frequency range featuring the use of Stochastic Collocation Method (SCM).
Several examples pertain to the analysis of planar and non-planar multilayer tissue models and to
the analysis of anatomically based realistic multi-layered models of the head exposed to radiation
from 5G communication systems.
The presentation is based on:

  • D. Poljak, Deterministic-Stochastic Modeling in Electromagnetic-Thermal Dosimetry, IEEE
    ICES Workshop on Computational Bioelectromagnetics (virtual), Feb. 2024.
  • D. Poljak, A Susnjara, Deterministic-Stochastic Modeling in Computational electromagnetics,
    IEEE Press/Wiley, New Jersey, 2024.

Dragan Poljak received his PhD in el. Eng. in 1996 from the Univ. of Split, Croatia. He is the Full Prof. at Dept. of Electron. and Computing, Univ. of Split. His research interests include computational electromagnetics (CEM), electromagnetic compatibility (EMC), bioelectromagnetics, ground penetrating radar (GPR), magnetohydrodynamics (MHD) and plasma physics). To date Prof. Poljak has published around 200 journal, and more than 300 conference papers, respectively, and authored some books, e.g. two by Wiley, one by IEEE Press, New Jersey and one by Elsevier, St Louis. He is a Senior member of IEEE, a member of Editorial Board of Eng. Anal. with Boundary Elements, Math. Problems in Eng. And IET Sci. Measur. & Techn. He was awarded by several prizes for his research achievements, such as National Prize for Science (2004 and 2023), Croatian sect. of IEEE annual Award (2016), Technical Achievement Award of the IEEE EMC Society (2019), George Green Medal from University of Mississippi (2021) and Certificate of Appreciation from IEEE Standards Associations (2022). From May 2013 to June 2021 Prof. Poljak was a member of the board of the Croatian Science Foundation. He was involved in ITER physics EUROfusion collaboration and he is currently involved in DONES EUROfusion collaboration and in Croatian Center for excellence in research for tech. sciences. He is active in few Working Groups of IEEE/Internat. Committee on Electromagnetic Safety (ICES) Tech. Comm. 95 SC6 EMF Dosimetry Modeling.