SAR variation study from 300 to 5000 MHz for 15 voxel models including different postures

Area of Science:

• Electromagnetics
• Computational Biology
• Medical Physics

Background:

• Specific Absorption Rate (SAR) is a critical metric for evaluating human exposure to radiofrequency (RF) fields.
• Existing guidelines by ICNIRP provide reference levels for safe exposure.
• Understanding SAR variations across different body sizes, frequencies, and exposure conditions is essential for accurate risk assessment.

Purpose of the Study:

• To extensively investigate the specific absorption rate (SAR) in various high-resolution whole-body voxel models.
• To analyze the influence of frequency (300 MHz to 5 GHz), incoming wave direction, polarization, body size, and posture on SAR.
• To compare SAR in homogeneous versus heterogeneous models and assess compliance with current ICNIRP guidelines.

Main Methods:

• Utilized the parallel finite-difference time-domain (FDTD) method for 720 simulations.
• Employed 15 voxel models representing a weight range of 18-105 kg.
• Irradiated models with plane waves at various directions and polarizations across the specified frequency range.

Main Results:

• Whole-body SAR and peak 10 g SAR were analyzed, revealing significant variations with frequency, direction, and polarization.
• Body size and posture influenced SAR, particularly at lower frequencies and around resonance.
• Homogeneous models underestimated whole-body SAR, especially around 2 GHz.
• The basic whole-body SAR restriction by ICNIRP was exceeded in smaller models (approx. 20 kg).

Conclusions:

• The effect of incoming direction and polarization on whole-body SAR is frequency-dependent and more pronounced at higher frequencies (GHz range).
• Current ICNIRP guidelines may require revision, with a specific need to lower reference levels between 2-5 GHz.
• Peak 10 g SAR limits were not exceeded in any studied case, suggesting they are currently adequate.