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Effective Analysis of Human Exposure Conditions with Body-worn Dosimeters in the 2.4 GHz Band
Published on: May 2, 2018
Computational dosimetry for grounded and ungrounded human models due to contact current
Kwok Hung Chan1, Junya Hattori, Ilkka Laakso
1Department of Computer Science and Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan. brian_chan@ieee.org
Physics in Medicine and Biology
|July 10, 2013
Summary
This study validates the quasi-static approximation for computational dosimetry of contact currents up to 3 MHz. It compares simulation results with international safety standards, finding discrepancies in extremities.
Area of Science:
- Computational physics
- Electromagnetics
- Biophysics
- Dosimetry
Background:
- Accurate computational dosimetry is crucial for assessing human exposure to electromagnetic fields.
- The quasi-static (QS) approximation offers a computationally efficient alternative to full-wave analysis for induced electric fields.
- Understanding contact current dosimetry is essential for human safety standards.
Purpose of the Study:
- To estimate the uncertainty of the quasi-static approximation for contact current dosimetry in grounded and ungrounded human models.
- To determine the upper frequency limit of the QS approximation for accurate in situ electric field and specific absorption rate (SAR) calculations.
- To compare computational dosimetry results with international safety guidelines and identify discrepancies.
Main Methods:
- Utilized the quasi-static finite-difference time-domain (QS-FDTD) method for grounded cylindrical and anatomical human models.
- Compared QS-FDTD results with analytical solutions (for grounded cylindrical models) and conventional FDTD (for anatomical models).
- Calculated induced electric fields and SAR for contact currents injected into a human finger model across a frequency range of 10 Hz to 100 MHz.
Main Results:
- The quasi-static approximation is valid up to 3 MHz with less than 10% relative local error, beyond which displacement current effects become significant.
- Maximum electric fields and SAR were observed not only in the finger but also in the wrist, forearm, and upper arm.
- Discrepancies were noted between basic restrictions for electric fields/SAR and reference levels for contact currents, particularly in extremities.
Conclusions:
- The QS approximation is a reliable method for contact current dosimetry below 3 MHz.
- Computational dosimetry reveals potential exposure concerns in human extremities, highlighting the need for careful consideration of current density and tissue properties.
- The study provides an equation relating current density, conductivity, and induced electric field, aiding in the assessment of safety standard discrepancies.
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