RF Safe

Importance of Exposure Duration and Metrics on Correlation between RF Energy Absorption and Temperature Increase in a Human Model

2018 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 1918

For plane-wave exposures across 700–2700 MHz, the best correlation with temperature increase generally occurred for exposure durations between 1 and 2 minutes for both SAR and VAR, with 1 g (SAR) or 1 cm^3 (VAR) averaging appearing optimal in that range. For …

Study snapshot

Publicationmanual · 2018
Study typeengineering
Reported directionUnclear
Evidence ratingInsufficient

Abstract

Importance of Exposure Duration and Metrics on Correlation between RF Energy Absorption and Temperature Increase in a Human Model Cavagnaro M, Lin J. Importance of exposure duration and metrics on correlation between RF energy absorption and temperature increase in a human model. IEEE Transactions on Biomedical Engineering. Dec 12, 2018. DOI: 10.1109/TBME.2018.2886475 Abstract Objective: This study investigated the influence of absorption metrics and averaging schemes on correlation between RF/microwave energy and induced temperature elevation for plane wave exposures. Methods: A voxel-based, anatomically realistic model of the human body was considered. Correlation of electromagnetic fields and temperature increases were evaluated at several frequencies. Both Specific Absorption Rate (SAR) and Volume Absorption Rate (VAR) were considered. Results: The best correlation with temperature increase occurs for exposure durations between 1 and 2 min both for SAR and VAR for most of the 700- to 2700-MHz frequencies considered. In this case, a 1-g mass or 1-cm3 volume appears to be optimal. However, for VAR, as frequency increases to above 900 MHz, a better correlation is achieved at slightly increased exposure times and volumes. For longer exposures, the maximum correlation coefficient is reduced, and the correlation favors larger averaging mass or volume. At steady-state (30 min), correlation of temperature increase with SAR is maximum for a mass of 9 g for all frequencies considered, whereas the volume for VAR maximum correlation is 15 cm3 for higher frequencies and 20 cm3 for lower frequencies. Conclusions: In general, SAR provides a better correlation with temperature compared to VAR for short exposures, while VAR renders better correlations for higher frequencies and longer exposures. Significance: The correlation between electromagnetic absorption and temperature increases has implications in guidelines for limiting human exposure to electromagnetic fields and in biomedical applications such as imaging, sensing, and hyperthermia. ieeexplore-ieee-org.libproxy.berkeley.edu

Machine Enhanced Logic

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
PopulationVoxel-based, anatomically realistic model of the human body
Sample sizeNot supplied
ExposureRF · 1–2 min; up to steady-state (30 min)
Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

For plane-wave exposures across 700–2700 MHz, the best correlation with temperature increase generally occurred for exposure durations between 1 and 2 minutes for both SAR and VAR, with 1 g (SAR) or 1 cm^3 (VAR) averaging appearing optimal in that range. For longer exposures, the maximum correlation coefficient was reduced and favored larger averaging mass/volume; at steady-state (30 min), maximum correlation with SAR occurred at 9 g for all frequencies, while VAR maximum correlation volumes were 15 cm^3 for higher frequencies and 20 cm^3 for lower frequencies. Overall, SAR correlated better with temperature for short exposures, whereas VAR correlated better for higher frequencies and longer exposures.

Outcomes measured

  • Correlation between RF/microwave absorption metrics (SAR, VAR) and induced temperature elevation
  • Optimal averaging mass/volume and exposure duration for correlation with temperature increase
View raw extracted JSON
{
  "study_type": "engineering",
  "exposure": {
    "band": "RF",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "1–2 min; up to steady-state (30 min)"
  },
  "population": "Voxel-based, anatomically realistic model of the human body",
  "sample_size": null,
  "outcomes": [
    "Correlation between RF/microwave absorption metrics (SAR, VAR) and induced temperature elevation",
    "Optimal averaging mass/volume and exposure duration for correlation with temperature increase"
  ],
  "main_findings": "For plane-wave exposures across 700–2700 MHz, the best correlation with temperature increase generally occurred for exposure durations between 1 and 2 minutes for both SAR and VAR, with 1 g (SAR) or 1 cm^3 (VAR) averaging appearing optimal in that range. For longer exposures, the maximum correlation coefficient was reduced and favored larger averaging mass/volume; at steady-state (30 min), maximum correlation with SAR occurred at 9 g for all frequencies, while VAR maximum correlation volumes were 15 cm^3 for higher frequencies and 20 cm^3 for lower frequencies. Overall, SAR correlated better with temperature for short exposures, whereas VAR correlated better for higher frequencies and longer exposures.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "RF",
    "microwave",
    "plane wave exposure",
    "specific absorption rate",
    "SAR",
    "volume absorption rate",
    "VAR",
    "temperature increase",
    "exposure duration",
    "averaging mass",
    "averaging volume",
    "human body model",
    "700–2700 MHz",
    "guidelines"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.55,
      "reason": "Discusses implications for guidelines limiting human exposure to electromagnetic fields and compares exposure metrics (SAR/VAR) relevant to guideline setting."
    }
  ]
}
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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/tbme.2018.2886475
PubMed: Not supplied

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