SAR Simulations & Safety

2017 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 1338

Study snapshot

Publicationmanual · 2017

Study typereview

Reported directionUnclear

Evidence ratingInsufficient

Abstract

SAR Simulations & Safety Fiedler TM, Ladd ME, Bitz AK. SAR Simulations & Safety. Neuroimage. 2017 Mar 20. pii: S1053-8119(17)30243-4. doi: 10.1016/j.neuroimage.2017.03.035. Abstract At ultra-high fields, the assessment of radiofrequency (RF) safety presents several new challenges compared to low-field systems. Multi-channel RF transmit coils in combination with parallel transmit techniques produce time-dependent and spatially varying power loss densities in the tissue. Further, in ultra-high-field systems, localized field effects can be more pronounced due to a transition from the quasistationary to the electromagnetic field regime. Consequently, local information on the RF field is required for reliable RF safety assessment as well as for monitoring of RF exposure during MR examinations. Numerical RF and thermal simulations for realistic exposure scenarios with anatomical body models are currently the only practical way to obtain the requisite local information on magnetic and electric field distributions as well as tissue temperature. In this article, safety regulations and the fundamental characteristics of RF field distributions in ultra-high-field systems are reviewed. Numerical methods for computation of RF fields as well as typical requirements for the analysis of realistic multi-channel RF exposure scenarios including anatomical body models are highlighted. In recent years, computation of the local tissue temperature has become of increasing interest, since a more accurate safety assessment is expected because temperature is directly related to tissue damage. Regarding thermal simulation, bio-heat transfer models and approaches for taking into account the physiological response of the human body to RF exposure are discussed. In addition, suitable methods are presented to validate calculated RF and thermal results with measurements. Finally, the concept of generalized simulation-based specific absorption rate (SAR) matrix models is discussed. These models can be incorporated into local SAR monitoring in multi-channel MR systems and allow the design of RF pulses under constraints for local SAR. ncbi.nlm.nih.gov

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 typereview

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureRF

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

The article reviews RF safety regulations and RF field distribution characteristics in ultra-high-field MRI, emphasizing that numerical RF and thermal simulations with anatomical body models are currently the only practical way to obtain local field and temperature information needed for reliable safety assessment and monitoring. It discusses bio-heat transfer modeling, physiological responses, validation methods, and generalized simulation-based SAR matrix models for local SAR monitoring and RF pulse design under SAR constraints.

Outcomes measured

RF safety assessment in ultra-high-field MRI
Local SAR (specific absorption rate) estimation/monitoring
RF and thermal (temperature) simulations
Tissue temperature / thermal dose considerations
Validation of RF/thermal simulations with measurements
SAR matrix models for local SAR monitoring and RF pulse design

View raw extracted JSON

{
  "study_type": "review",
  "exposure": {
    "band": "RF",
    "source": "MRI (ultra-high-field, multi-channel transmit coils/parallel transmit)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "RF safety assessment in ultra-high-field MRI",
    "Local SAR (specific absorption rate) estimation/monitoring",
    "RF and thermal (temperature) simulations",
    "Tissue temperature / thermal dose considerations",
    "Validation of RF/thermal simulations with measurements",
    "SAR matrix models for local SAR monitoring and RF pulse design"
  ],
  "main_findings": "The article reviews RF safety regulations and RF field distribution characteristics in ultra-high-field MRI, emphasizing that numerical RF and thermal simulations with anatomical body models are currently the only practical way to obtain local field and temperature information needed for reliable safety assessment and monitoring. It discusses bio-heat transfer modeling, physiological responses, validation methods, and generalized simulation-based SAR matrix models for local SAR monitoring and RF pulse design under SAR constraints.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "specific absorption rate",
    "SAR",
    "RF safety",
    "ultra-high-field MRI",
    "parallel transmit",
    "multi-channel transmit coils",
    "numerical simulation",
    "thermal simulation",
    "bio-heat transfer",
    "tissue temperature",
    "local SAR monitoring",
    "SAR matrix models"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.42,
      "reason": "Discusses safety regulations for RF exposure in the context of MRI."
    }
  ]
}

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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: 10.1016/j.neuroimage.2017.03.035
PubMed: Not supplied

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