Dosimetry of Various Human Bodies Exposed to Microwave Broadband Electromagnetic Pulses

2021 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 1056

Study snapshot

Publicationmanual · 2021

Study typeexposure_assessment

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Dosimetry of Various Human Bodies Exposed to Microwave Broadband Electromagnetic Pulses Jerdvisanop Chakarothai, Wake Kanako, Fujii Katsumi. Dosimetry of Various Human Bodies Exposed to Microwave Broadband Electromagnetic Pulses. Frontiers in Public Health. 9:1182. 2021. doi:10.3389/fpubh.2021.725310. Abstract In this paper, human exposures to ultra-wideband (UWB) electromagnetic (EM) pulses in the microwave region are assessed using a frequency-dependent FDTD scheme previously proposed by the authors. Complex permittivity functions of all biological tissues used in the numerical analyses are accurately expressed by the four-term Cole–Cole model. In our method, we apply the fast inverse Laplace transform to determine the time- domain impulse response, utilize the Prony method to find the Z-domain representation, and extract residues and poles for use in the FDTD formulation. Update equations for the electric field are then derived via the Z- transformation. Firstly, we perform reflection and transmission analyses of a multilayer composed of six different biological tissues and then confirm the validity of the proposed method by comparison with analytical results. Finally, numerical dosimetry of various human bodies exposed to EM pulses from the front in the microwave frequency range is performed, and the specific energy absorption is evaluated and compared with that prescribed in international guidelines. Conclusion We have performed numerical dosimetry on human bodies illuminated by an EM pulse from the front by using the (FD)2TD method, previously proposed by the authors. The method fully considers broadband characteristics of the complex relative permittivity of the biological media used in the analysis model via the application of the FILT and the Prony method. Firstly, we demonstrated the validity of the update coefficients, i.e., the residues and poles of the expression for the IIR in the z-domain, by comparing the numerical reflection coefficients with those derived from the EM theory. It was clarified that the numerical results within 2% of those obtained theoretically over a broad frequency range from 50 MHz to 10 GHz, demonstrating the validity of the proposed approach. It was also found that the transmission characteristics of the EM pulse into the CSF layer of a multilayer mimicking a human head are almost flat over a frequency range between 300 and 800 MHz and that the transmission decreases with increasing EM traveling distance from the skin boundary due to higher energy absorption at superficial biological tissues such as “Skin” and “Fat” when the frequency is higher than 1 GHz. Therefore, most of the pulse energy that penetrates into the biological body has a frequency below 1 GHz. Then, numerical dosimetry of various human models exposed to an EM pulse having a frequency component of up to ~1.3 GHz was performed. The whole-body average SAR at 24 frequencies was determined by a single run of broadband FDTD simulations. The results matched those published in the literature, demonstrating the validity and availability of the proposed FDTD method. Then the SA distribution of each numerical model was determined, and it was found that the maximum SA occurs at the hands and neck for the ungrounded model, while they appear at the hands and ankle when the model is grounded. The maximum SA value was 0.290 pJ/kg for an incident electric field strength of 1 V/m or 0.437 nJ/kg for an incident power density of 2 W/m2. It has been shown for the first time that, by using our proposed FDTD approach with the FILT and the Prony method, we can obtain quantitatively detailed information on SA that can be compared with the limits prescribed in international guidelines or standards. Open access paper: frontiersin.org

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeexposure_assessment

Effect directionunclear

PopulationVarious numerical human body models (computational dosimetry)

Sample sizeNot supplied

Exposuremicrowave

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Using a frequency-dependent FDTD approach, the authors performed numerical dosimetry of human models exposed to microwave-region UWB EM pulses and evaluated specific energy absorption and whole-body average SAR for comparison with international guideline limits. Numerical reflection coefficients agreed within 2% of theoretical values over 50 MHz to 10 GHz, and dosimetry results matched previously published literature. Maximum SA locations differed by grounding condition (hands/neck ungrounded; hands/ankle grounded), with a reported maximum SA of 0.290 pJ/kg for 1 V/m incident field or 0.437 nJ/kg for 2 W/m^2 incident power density.

Outcomes measured

Whole-body average SAR
Specific energy absorption (SA)
Reflection and transmission characteristics in multilayer biological tissue model

Limitations

Computational/numerical study (no direct health outcomes assessed)
Exposure scenario limited to front-incident EM pulse illumination and modeled grounding conditions
Specific details on number/types of human models (sample size) not stated in the abstract

View raw extracted JSON

{
  "study_type": "exposure_assessment",
  "exposure": {
    "band": "microwave",
    "source": "ultra-wideband (UWB) electromagnetic pulses (front-incident illumination)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "Various numerical human body models (computational dosimetry)",
  "sample_size": null,
  "outcomes": [
    "Whole-body average SAR",
    "Specific energy absorption (SA)",
    "Reflection and transmission characteristics in multilayer biological tissue model"
  ],
  "main_findings": "Using a frequency-dependent FDTD approach, the authors performed numerical dosimetry of human models exposed to microwave-region UWB EM pulses and evaluated specific energy absorption and whole-body average SAR for comparison with international guideline limits. Numerical reflection coefficients agreed within 2% of theoretical values over 50 MHz to 10 GHz, and dosimetry results matched previously published literature. Maximum SA locations differed by grounding condition (hands/neck ungrounded; hands/ankle grounded), with a reported maximum SA of 0.290 pJ/kg for 1 V/m incident field or 0.437 nJ/kg for 2 W/m^2 incident power density.",
  "effect_direction": "unclear",
  "limitations": [
    "Computational/numerical study (no direct health outcomes assessed)",
    "Exposure scenario limited to front-incident EM pulse illumination and modeled grounding conditions",
    "Specific details on number/types of human models (sample size) not stated in the abstract"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "dosimetry",
    "ultra-wideband",
    "UWB",
    "microwave",
    "FDTD",
    "Cole-Cole model",
    "specific absorption rate",
    "SAR",
    "specific energy absorption",
    "SA",
    "international guidelines",
    "grounded model",
    "ungrounded model",
    "50 MHz",
    "10 GHz"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.62,
      "reason": "Explicit comparison of computed SAR/SA with limits prescribed in international guidelines/standards."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.3389/fpubh.2021.725310
PubMed: Not supplied

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