RF Safe

The relationship of temperature rise to specific absorption rate and current in the human leg for exposure to electromagnetic radiation in the high frequency band.

Physics in medicine and biology · 2003 · Unclear · Low evidence

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UnclearLow evidencePaper 6392

Using a finite element approximation of the Pennes bioheat equation, the paper derives a heating factor (deltaT/SAR) for a human leg exposure scenario in the HF band and examines sensitivity to blood perfusion and a simple local thermoregulatory model. The re…

Study snapshot

PublicationPhysics in medicine and biology · 2003
Study typeengineering
Reported directionUnclear
Evidence ratingLow

Abstract

Of the biological effects of human exposure to radiofrequency and microwave radiation, the best-established are those due to elevation of tissue temperature. To prevent harmful levels of heating, restrictions have been proposed on the specific absorption rate (SAR). However, the relationship between SAR and temperature rise is not an invariant, since not only the heat capacity but also the efficiency of heat dissipation varies between different tissues and exposure scenarios. For small enough SAR, the relationship is linear and may be characterized by a 'heating factor' deltaT/SAR. Under whole-body irradiation the SAR may be particularly high in the ankles due to the concentration of current flowing through a relatively small cross-sectional area. In a previous paper, the author has presented calculations of the SAR distribution in a human leg in the high frequency (HF) band. In this paper, the heating factor for this situation is derived using a finite element approximation of the Pennes bioheat equation. The sensitivity of the results to different blood perfusion rates is investigated, and a simple local thermoregulatory model is applied. Both time-dependent and steady-state solutions are considered. Results confirm the appropriateness of the ICNIRP reference level of 100 mA on current through the leg, but suggest that at higher currents significant thermoregulatory adjustments to muscle blood flow will occur.

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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
Populationhuman leg (computational model)
Sample sizeNot supplied
ExposureHF
Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

Using a finite element approximation of the Pennes bioheat equation, the paper derives a heating factor (deltaT/SAR) for a human leg exposure scenario in the HF band and examines sensitivity to blood perfusion and a simple local thermoregulatory model. The results are reported as confirming the appropriateness of the ICNIRP reference level of 100 mA for current through the leg, while suggesting that higher currents may trigger significant thermoregulatory adjustments to muscle blood flow.

Outcomes measured

  • Temperature rise (deltaT)
  • Specific absorption rate (SAR) distribution/relationship to temperature rise
  • Current through the leg (mA)
  • Heating factor (deltaT/SAR)
  • Thermoregulatory adjustments (muscle blood flow)

Limitations

  • Modeling/simulation study (finite element bioheat equation) rather than direct measurements in humans
  • Frequency, SAR levels, and exposure duration not specified in the abstract
  • Details of model validation and parameter choices (e.g., perfusion rates) not provided in the abstract
View raw extracted JSON
{
  "study_type": "engineering",
  "exposure": {
    "band": "HF",
    "source": "whole-body irradiation (current through the leg)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "human leg (computational model)",
  "sample_size": null,
  "outcomes": [
    "Temperature rise (deltaT)",
    "Specific absorption rate (SAR) distribution/relationship to temperature rise",
    "Current through the leg (mA)",
    "Heating factor (deltaT/SAR)",
    "Thermoregulatory adjustments (muscle blood flow)"
  ],
  "main_findings": "Using a finite element approximation of the Pennes bioheat equation, the paper derives a heating factor (deltaT/SAR) for a human leg exposure scenario in the HF band and examines sensitivity to blood perfusion and a simple local thermoregulatory model. The results are reported as confirming the appropriateness of the ICNIRP reference level of 100 mA for current through the leg, while suggesting that higher currents may trigger significant thermoregulatory adjustments to muscle blood flow.",
  "effect_direction": "unclear",
  "limitations": [
    "Modeling/simulation study (finite element bioheat equation) rather than direct measurements in humans",
    "Frequency, SAR levels, and exposure duration not specified in the abstract",
    "Details of model validation and parameter choices (e.g., perfusion rates) not provided in the abstract"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "high frequency (HF)",
    "radiofrequency",
    "microwave",
    "tissue heating",
    "temperature rise",
    "specific absorption rate",
    "SAR",
    "Pennes bioheat equation",
    "finite element",
    "blood perfusion",
    "thermoregulation",
    "ICNIRP",
    "reference level",
    "current through leg",
    "ankle"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.86,
      "reason": "Abstract explicitly evaluates/mentions ICNIRP reference level (100 mA) for current through the leg."
    }
  ]
}
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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: 10.1088/0031-9155/48/19/004
PubMed: 14579857

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