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Correction of main and transmit magnetic field (B0 and B1) inhomogeneity effects in multicomponent-driven equilibrium single-pulse observation of T1 and T2.

Magnetic resonance in medicine · 2011 · No effect · Insufficient evidence

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The authors describe correction methods for B1 (via DESPOT1-HIFI flip-angle calibration) and B0 (via an added fitting parameter plus multiple phase-cycled bSSFP acquisitions) in multicomponent-driven equilibrium single-pulse observation of T1/T2. Numerical si…

Study snapshot

PublicationMagnetic resonance in medicine · 2011
Study typeengineering
Reported directionNo effect
Evidence ratingInsufficient

Abstract

Multicomponent-driven equilibrium single-component observation of T(1) and T(2) offers a new approach to multiple component relaxation time and myelin water analysis. The method derives two-component relaxation information from spoiled and fully balanced steady-state (SPGR and bSSFP) imaging data acquired over multiple flip angles. Although these steady-state imaging techniques afford rapid acquisition times and high signal-to-noise ratio efficiency, they are also sensitive to main (B(0) ) and transmit (B(1) ) magnetic field inhomogeneities. These effects alter the measured signal from their theoretical values and lead to substantive errors in the derived myelin volume fraction estimates. Here, we incorporate correction techniques to mitigate these effects. DESPOT1-HIFI is used to first calibrate the transmitted flip angles; and B(0) affects are removed through the inclusion of an additional parameter in the multicomponent-driven equilibrium single-component observation of T(1) and T(2) fitting, coupled with the acquisition of multiple phase-cycled bSSFP data. The performance of these correction techniques was evaluated using numerical simulations, demonstrating effective removal of B(0) and B(1)-induced errors in the derived myelin fraction relaxation parameters. The approach was also successfully demonstrated in vivo, with near artifact-free whole-brain, high spatial resolution (1.7 mm × 1.7 mm × 1.7 mm isotropic voxels) myelin water fraction maps acquired in a clinically feasible 16 min.

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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 directionno_effect
PopulationNot supplied
Sample sizeNot supplied
ExposureNot supplied
Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

The authors describe correction methods for B1 (via DESPOT1-HIFI flip-angle calibration) and B0 (via an added fitting parameter plus multiple phase-cycled bSSFP acquisitions) in multicomponent-driven equilibrium single-pulse observation of T1/T2. Numerical simulations showed effective removal of B0- and B1-induced errors in derived myelin fraction relaxation parameters, and the approach was demonstrated in vivo with near artifact-free whole-brain myelin water fraction maps acquired in 16 minutes.

Outcomes measured

  • B0 inhomogeneity effects on steady-state MRI signal
  • B1 (transmit flip angle) inhomogeneity effects on steady-state MRI signal
  • Errors in derived myelin volume fraction / myelin water fraction estimates
  • Performance of correction techniques (DESPOT1-HIFI calibration; B0 parameter + phase-cycled bSSFP)
  • Image quality of whole-brain myelin water fraction maps (artifact reduction)
View raw extracted JSON
{
  "study_type": "engineering",
  "exposure": {
    "band": null,
    "source": "MRI (B0 and B1 magnetic fields)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "B0 inhomogeneity effects on steady-state MRI signal",
    "B1 (transmit flip angle) inhomogeneity effects on steady-state MRI signal",
    "Errors in derived myelin volume fraction / myelin water fraction estimates",
    "Performance of correction techniques (DESPOT1-HIFI calibration; B0 parameter + phase-cycled bSSFP)",
    "Image quality of whole-brain myelin water fraction maps (artifact reduction)"
  ],
  "main_findings": "The authors describe correction methods for B1 (via DESPOT1-HIFI flip-angle calibration) and B0 (via an added fitting parameter plus multiple phase-cycled bSSFP acquisitions) in multicomponent-driven equilibrium single-pulse observation of T1/T2. Numerical simulations showed effective removal of B0- and B1-induced errors in derived myelin fraction relaxation parameters, and the approach was demonstrated in vivo with near artifact-free whole-brain myelin water fraction maps acquired in 16 minutes.",
  "effect_direction": "no_effect",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "MRI",
    "B0 inhomogeneity",
    "B1 inhomogeneity",
    "DESPOT1-HIFI",
    "SPGR",
    "bSSFP",
    "phase-cycled bSSFP",
    "T1",
    "T2",
    "myelin water fraction",
    "myelin volume fraction",
    "correction techniques",
    "numerical simulations",
    "in vivo"
  ],
  "suggested_hubs": [
    {
      "slug": "engineering-mri",
      "weight": 0.78,
      "reason": "Focuses on MRI acquisition/modeling methods to correct B0/B1 inhomogeneity artifacts rather than health effects."
    }
  ]
}
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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/mrm.22685
PubMed: 21413066

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