A radiofrequency coil to facilitate B₁⁺ shimming and parallel imaging acceleration in three dimensions at 7 T.

NMR in biomedicine · 2011 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3261

Study snapshot

PublicationNMR in biomedicine · 2011

Study typeengineering

Reported directionUnclear

Evidence ratingInsufficient

Abstract

A 15-channel transmit-receive (transceive) radiofrequency (RF) coil was developed to image the human brain at 7 T. A hybrid decoupling scheme was implemented that used both capacitive decoupling and the partial geometric overlapping of adjacent coil elements. The decoupling scheme allowed coil elements to be arrayed along all three Cartesian axes; this facilitated shimming of the transmit field, B₁⁺, and parallel imaging acceleration along the longitudinal direction in addition to the standard transverse directions. Each channel was independently controlled during imaging using a 16-channel console and a 16 × 1-kW RF amplifier-matrix. The mean isolation between all combinations of coil elements was 18 ± 7 dB. After B₁⁺ shimming, the standard deviation of the transmit field uniformity was 11% in an axial plane and 32% over the entire brain superior to the mid-cerebellum. Transmit uniformity was sufficient to acquire fast spin echo images of this region of the brain with a single B₁⁺ shim solution. Signal-to-noise ratio (SNR) maps showed higher SNR in the periphery vs center of the brain, and higher SNR in the occipital and temporal lobes vs the frontal lobe. Parallel imaging acceleration in a rostral-caudal oblique plane was demonstrated. The implication of the number of channels in a transmit-receive coil was discussed: it was determined that improvements in SNR and B₁⁺ shimming can be expected when using more than 15 independently controlled transmit-receive channels.

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AI evidence extraction

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Study typeengineering

Effect directionunclear

PopulationHumans (brain imaging)

Sample sizeNot supplied

ExposureRF

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

A 15-channel transmit-receive RF coil for 7 T human brain imaging was developed using a hybrid decoupling scheme (capacitive decoupling plus partial geometric overlap), enabling element arrangement along three Cartesian axes. Mean isolation between coil elements was 18 ± 7 dB. After B1+ shimming, transmit field uniformity standard deviation was 11% in an axial plane and 32% over the entire brain superior to the mid-cerebellum; uniformity was sufficient to acquire fast spin echo images with a single shim solution, and parallel imaging acceleration in a rostral-caudal oblique plane was demonstrated.

Outcomes measured

RF coil design and decoupling performance (isolation, dB)
B1+ shimming performance (transmit field uniformity)
Image quality metrics (SNR distribution)
Parallel imaging acceleration feasibility

Limitations

Sample size not reported in the abstract
No explicit health/biological outcomes reported (focus is technical performance)
RF exposure metrics (e.g., frequency, SAR) not reported in the abstract

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": "RF",
    "source": "MRI RF coil (7 T brain imaging)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": "Humans (brain imaging)",
  "sample_size": null,
  "outcomes": [
    "RF coil design and decoupling performance (isolation, dB)",
    "B1+ shimming performance (transmit field uniformity)",
    "Image quality metrics (SNR distribution)",
    "Parallel imaging acceleration feasibility"
  ],
  "main_findings": "A 15-channel transmit-receive RF coil for 7 T human brain imaging was developed using a hybrid decoupling scheme (capacitive decoupling plus partial geometric overlap), enabling element arrangement along three Cartesian axes. Mean isolation between coil elements was 18 ± 7 dB. After B1+ shimming, transmit field uniformity standard deviation was 11% in an axial plane and 32% over the entire brain superior to the mid-cerebellum; uniformity was sufficient to acquire fast spin echo images with a single shim solution, and parallel imaging acceleration in a rostral-caudal oblique plane was demonstrated.",
  "effect_direction": "unclear",
  "limitations": [
    "Sample size not reported in the abstract",
    "No explicit health/biological outcomes reported (focus is technical performance)",
    "RF exposure metrics (e.g., frequency, SAR) not reported in the abstract"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "7 T",
    "MRI",
    "radiofrequency coil",
    "transmit-receive",
    "15-channel",
    "B1+ shimming",
    "parallel imaging",
    "decoupling",
    "SNR"
  ],
  "suggested_hubs": [
    {
      "slug": "engineering-mri",
      "weight": 0.9,
      "reason": "Development and performance characterization of a 15-channel transceive RF coil for 7 T brain MRI, including B1+ shimming and parallel imaging."
    }
  ]
}

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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: 10.1002/nbm.1627
PubMed: 21834005

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