Variability in EMF permittivity values: implications for SAR calculations.

IEEE transactions on bio-medical engineering · 2000 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 5353

Study snapshot

PublicationIEEE transactions on bio-medical engineering · 2000

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Digital anatomical models of man and animals are available for use in numerical calculations to predict electromagnetic field (EMF)-induced specific absorption rate (SAR) values. To use these models, permittivity values are assigned to the various tissues for the EMF frequencies of interest. There is, as yet, no consensus on what are the best permittivity data. This study analyzed the variability in published permittivity data and investigated the effects of permittivity values that are proportional on SAR calculations. Whole-sphere averaged and localized SAR values along the diameter of a 4-cm sphere are calculated for EMF exposures in the radio frequency range of 1 MHz to 1 GHz. When the dimensions of a sphere are small compared to the wavelength (i.e., wavelength inside the material is greater than ten times the dimensions of the object), the whole-sphere averaged SAR is inversely proportional to the permittivity of the material composing the sphere. However, the localized SAR values generally do not have the same relation and, as a matter of fact, vary greatly depending on the location within the sphere. These results indicate that care must be taken in choosing the permittivity values used in calculating SAR values and some estimate of the dependence of the calculated SAR values on variability in permittivity should be determined.

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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 typeengineering

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureRF

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

The study analyzed variability in published tissue permittivity data and evaluated how proportional changes in permittivity affect SAR calculations for RF exposures from 1 MHz to 1 GHz using a 4-cm sphere model. When the sphere dimensions are small relative to wavelength, whole-sphere averaged SAR was inversely proportional to permittivity, while localized SAR did not follow the same relationship and varied substantially by location within the sphere.

Outcomes measured

Specific absorption rate (SAR) calculation sensitivity to permittivity variability
Whole-sphere averaged SAR dependence on permittivity
Localized SAR spatial variability within a sphere

Limitations

Analysis is based on a simplified 4-cm sphere model rather than full anatomical models
No specific permittivity datasets or quantitative variability ranges are provided in the abstract
Findings pertain to SAR calculation sensitivity and may not directly translate to biological or health outcomes

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": "RF",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Specific absorption rate (SAR) calculation sensitivity to permittivity variability",
    "Whole-sphere averaged SAR dependence on permittivity",
    "Localized SAR spatial variability within a sphere"
  ],
  "main_findings": "The study analyzed variability in published tissue permittivity data and evaluated how proportional changes in permittivity affect SAR calculations for RF exposures from 1 MHz to 1 GHz using a 4-cm sphere model. When the sphere dimensions are small relative to wavelength, whole-sphere averaged SAR was inversely proportional to permittivity, while localized SAR did not follow the same relationship and varied substantially by location within the sphere.",
  "effect_direction": "unclear",
  "limitations": [
    "Analysis is based on a simplified 4-cm sphere model rather than full anatomical models",
    "No specific permittivity datasets or quantitative variability ranges are provided in the abstract",
    "Findings pertain to SAR calculation sensitivity and may not directly translate to biological or health outcomes"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "permittivity",
    "dielectric properties",
    "variability",
    "SAR",
    "specific absorption rate",
    "numerical modeling",
    "digital anatomical models",
    "radio frequency",
    "1 MHz",
    "1 GHz"
  ],
  "suggested_hubs": [
    {
      "slug": "exposure-assessment",
      "weight": 0.78,
      "reason": "Focuses on how permittivity assumptions affect RF SAR calculations in numerical models."
    }
  ]
}

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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: 10.1109/10.827308
PubMed: 10743782

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