Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5 T (1 GHz) and beyond.

Magma (New York, N.Y.) · 2016 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 4865

Study snapshot

PublicationMagma (New York, N.Y.) · 2016

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

OBJECTIVE: This work investigates electrodynamic constraints, explores RF antenna concepts and examines the transmission fields (B 1 (+) ) and RF power deposition of dipole antenna arrays for (1)H magnetic resonance of the human brain at 1 GHz (23.5 T). MATERIALS AND METHODS: Electromagnetic field (EMF) simulations are performed in phantoms with average tissue simulants for dipole antennae using discrete frequencies [300 MHz (7.0 T) to 3 GHz (70.0 T)]. To advance to a human setup EMF simulations are conducted in anatomical human voxel models of the human head using a 20-element dipole array operating at 1 GHz. RESULTS: Our results demonstrate that transmission fields suitable for (1)H MR of the human brain can be achieved at 1 GHz. An increase in transmit channel density around the human head helps to enhance B 1 (+) in the center of the brain. The calculated relative increase in specific absorption rate at 23.5 versus 7.0 T was below 1.4 (in-phase phase setting) and 2.7 (circular polarized phase setting) for the dipole antennae array. CONCLUSION: The benefits of multi-channel dipole antennae at higher frequencies render MR at 23.5 T feasible from an electrodynamic standpoint. This very preliminary finding opens the door on further explorations that might be catalyzed into a 20-T class human MR system.

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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 · 1000 MHz

Evidence strengthInsufficientConfidence: 78% · Peer reviewed: yes

Main findings

EMF simulations in phantoms and anatomical human head voxel models suggest that transmission fields suitable for 1H brain MR can be achieved at 1 GHz (23.5 T). Increasing transmit channel density around the head enhanced B1+ in the brain center. The calculated relative SAR increase at 23.5 T versus 7.0 T was below 1.4 (in-phase) and 2.7 (circular polarized) for the dipole array.

Outcomes measured

Transmission fields (B1+)
RF power deposition
Specific absorption rate (SAR) (relative increase at 23.5 T vs 7.0 T)

Limitations

Simulation-based study (EMF simulations in phantoms and voxel models)
Described as a "very preliminary" finding
SAR results reported as relative increase; absolute SAR not provided in abstract

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": "RF",
    "source": "MRI (human magnetic resonance) dipole antenna array",
    "frequency_mhz": 1000,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Transmission fields (B1+)",
    "RF power deposition",
    "Specific absorption rate (SAR) (relative increase at 23.5 T vs 7.0 T)"
  ],
  "main_findings": "EMF simulations in phantoms and anatomical human head voxel models suggest that transmission fields suitable for 1H brain MR can be achieved at 1 GHz (23.5 T). Increasing transmit channel density around the head enhanced B1+ in the brain center. The calculated relative SAR increase at 23.5 T versus 7.0 T was below 1.4 (in-phase) and 2.7 (circular polarized) for the dipole array.",
  "effect_direction": "unclear",
  "limitations": [
    "Simulation-based study (EMF simulations in phantoms and voxel models)",
    "Described as a \"very preliminary\" finding",
    "SAR results reported as relative increase; absolute SAR not provided in abstract"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "MRI",
    "ultra-high field",
    "23.5 T",
    "1 GHz",
    "dipole antenna array",
    "B1+",
    "RF power deposition",
    "SAR",
    "EMF simulations",
    "human head voxel model",
    "phantom"
  ],
  "suggested_hubs": []
}

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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: 10.1007/s10334-016-0559-y
PubMed: 27097905

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