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Variability in EMF permittivity values: implications for SAR calculations
W D Hurt1, J M Ziriax, P A Mason
1Air Force Research Laboratory, Directed Energy Bioeffects Division, Brooks AFB, TX 78235-5324, USA. william.hurt@brooks.af.mil
IEEE Transactions on Bio-Medical Engineering
|April 1, 2000
Summary
Choosing accurate permittivity data is crucial for predicting electromagnetic field (EMF)-induced specific absorption rate (SAR) values. Variability in permittivity significantly impacts localized SAR calculations, necessitating careful selection and sensitivity analysis.
Area of Science:
- Biophysics
- Computational Electromagnetics
- Medical Physics
Background:
- Digital anatomical models are used for calculating electromagnetic field (EMF)-induced specific absorption rate (SAR) values.
- Accurate tissue permittivity data is essential for these calculations, but consensus is lacking.
Purpose of the Study:
- To analyze the variability in published permittivity data.
- To investigate the impact of permittivity variations on SAR calculations.
Main Methods:
- Calculated whole-sphere averaged and localized SAR values for a 4-cm sphere.
- Simulated EMF exposures from 1 MHz to 1 GHz.
- Assessed the relationship between permittivity and SAR values.
Main Results:
- Whole-sphere averaged SAR is inversely proportional to permittivity when object dimensions are small relative to wavelength.
- Localized SAR values show significant spatial variation and do not follow the same trend.
- Permittivity variability greatly affects localized SAR calculations.
Conclusions:
- Careful selection of permittivity values is vital for accurate SAR calculations.
- Estimating the dependence of SAR on permittivity variability is recommended.
- The findings highlight the importance of data quality in computational dosimetry.