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Measurements of time characteristics of the gradient magnetic field.

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference · 2005 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 3535

The authors developed a simple method to measure the time course of MRI gradient pulses of either polarity and report that it was experimentally tested on a 4.7 T tomograph. The method uses instantaneous MR frequency measurements during a gradient pulse after…

Study snapshot

PublicationConference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference · 2005
Study typeengineering
Reported directionUnclear
Evidence ratingInsufficient

Abstract

Imaging techniques based on the principles of nuclear magnetic resonance (NMR) are modern techniques for the study of chemical, biological and physical properties of substances. The most important are their applications in medical sciences. MR imaging of a specimen weighted with diffusion coefficients requires very accurate data on the time course of the gradient pulse. Diffusion coefficients are determined from the drop of the MR signal measured with and without the application of magnetic field gradients. From the accuracy point of view, the defined course of gradients plays an important role in the computation of coefficients. A minimum rise and fall times, a defined magnitude of the excited gradient of the magnetic field and a symmetry of positive and negative pulses (zero integral of pulses of the same magnitude and opposite polarities) are required. To characterize the time course of gradient pulses or either polarity, simple methods of their measurement has been developed and experimentally tested on a 4.7 T tomograph. The method is based on the principle of instantaneous MR frequency measurements at the presence of a gradient pulse following the excitation of a thin layer situated outside the centre of the gradient field.

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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
ExposureNot supplied
Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

The authors developed a simple method to measure the time course of MRI gradient pulses of either polarity and report that it was experimentally tested on a 4.7 T tomograph. The method uses instantaneous MR frequency measurements during a gradient pulse after excitation of a thin layer located outside the center of the gradient field.

Outcomes measured

  • Time course characteristics of MRI gradient pulses (rise/fall times, magnitude, symmetry/zero integral)
  • Accuracy of gradient pulse measurement method based on instantaneous MR frequency measurements

Limitations

  • No health/biological outcomes reported in the abstract
  • No quantitative results or performance metrics reported in the abstract
  • Sample size and experimental details not provided in the abstract
View raw extracted JSON
{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "MRI gradient magnetic field",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "Time course characteristics of MRI gradient pulses (rise/fall times, magnitude, symmetry/zero integral)",
    "Accuracy of gradient pulse measurement method based on instantaneous MR frequency measurements"
  ],
  "main_findings": "The authors developed a simple method to measure the time course of MRI gradient pulses of either polarity and report that it was experimentally tested on a 4.7 T tomograph. The method uses instantaneous MR frequency measurements during a gradient pulse after excitation of a thin layer located outside the center of the gradient field.",
  "effect_direction": "unclear",
  "limitations": [
    "No health/biological outcomes reported in the abstract",
    "No quantitative results or performance metrics reported in the abstract",
    "Sample size and experimental details not provided in the abstract"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "MRI",
    "NMR",
    "gradient magnetic field",
    "gradient pulse",
    "time course",
    "diffusion coefficients",
    "measurement method",
    "4.7 T tomograph"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.2,
      "reason": "MRI gradient field measurement may relate to MRI environment exposure, but no occupational or health focus is stated."
    }
  ]
}
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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/iembs.2005.1616669
PubMed: 17282438

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