Simple algorithm for the correction of MRI image artefacts due to random phase fluctuations

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6 Downloads (Pure)

Abstract

Purpose

Fast Field-Cycling (FFC) MRI is a novel technology that allows varying the main magnetic field B0 during the pulse sequence, from the nominal field (usually hundreds of millitesla) down to Earth's field or below. This technique uses resistive magnets powered by fast amplifiers. One of the challenges with this method is to stabilise the magnetic field during the acquisition of the NMR signal. Indeed, a typical consequence of field instability is small, random phase variations between each line of k-space resulting in artefacts, similar to those which occur due to homogeneous motion but harder to correct as no assumption can be made about the phase error, which appears completely random. Here we propose an algorithm that can correct for the random phase variations induced by field instabilities without prior knowledge about the phase error.

Methods

The algorithm exploits the fact that ghosts caused by field instability manifest in image regions which should be signal free. The algorithm minimises the signal in the background by finding an optimum phase correction for each line of k-space and repeats the operation until the result converges, leaving the background free of signal.

Conclusion

We showed the conditions for which the algorithm is robust and successfully applied it on images acquired on FFC-MRI scanners. The same algorithm can be used for various applications other than Fast Field-Cycling MRI.
Original languageEnglish
Pages (from-to)55-59
Number of pages5
JournalMagnetic Resonance Imaging
Volume44
Early online date24 Jul 2017
DOIs
Publication statusPublished - Dec 2017

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Magnetic resonance imaging
Artifacts
Magnetic Fields
Magnetic fields
Magnets
Earth (planet)
Nuclear magnetic resonance
Technology

Keywords

  • Fast field-cycling MRI
  • Phase encode artefact
  • Correction algorithm
  • Post-processing

Cite this

@article{0b40775117164ec7bdd4474cbe3fade9,
title = "Simple algorithm for the correction of MRI image artefacts due to random phase fluctuations",
abstract = "PurposeFast Field-Cycling (FFC) MRI is a novel technology that allows varying the main magnetic field B0 during the pulse sequence, from the nominal field (usually hundreds of millitesla) down to Earth's field or below. This technique uses resistive magnets powered by fast amplifiers. One of the challenges with this method is to stabilise the magnetic field during the acquisition of the NMR signal. Indeed, a typical consequence of field instability is small, random phase variations between each line of k-space resulting in artefacts, similar to those which occur due to homogeneous motion but harder to correct as no assumption can be made about the phase error, which appears completely random. Here we propose an algorithm that can correct for the random phase variations induced by field instabilities without prior knowledge about the phase error.MethodsThe algorithm exploits the fact that ghosts caused by field instability manifest in image regions which should be signal free. The algorithm minimises the signal in the background by finding an optimum phase correction for each line of k-space and repeats the operation until the result converges, leaving the background free of signal.ConclusionWe showed the conditions for which the algorithm is robust and successfully applied it on images acquired on FFC-MRI scanners. The same algorithm can be used for various applications other than Fast Field-Cycling MRI.",
keywords = "Fast field-cycling MRI, Phase encode artefact, Correction algorithm, Post-processing",
author = "Broche, {Lionel M.} and Ross, {P. James} and Davies, {Gareth R.} and Lurie, {David J.}",
note = "Grant support: This work was supported by EPSRC [grant numbers EP/E036775/1, EP/K020293/1] and received funding from the European Union's Horizon 2020 research and innovation programme [grant agreement No 668119, project “IDentIFY”]",
year = "2017",
month = "12",
doi = "10.1016/j.mri.2017.07.023",
language = "English",
volume = "44",
pages = "55--59",
journal = "Magnetic Resonance Imaging",
issn = "0730-725X",
publisher = "Elsevier",

}

TY - JOUR

T1 - Simple algorithm for the correction of MRI image artefacts due to random phase fluctuations

AU - Broche, Lionel M.

AU - Ross, P. James

AU - Davies, Gareth R.

AU - Lurie, David J.

N1 - Grant support: This work was supported by EPSRC [grant numbers EP/E036775/1, EP/K020293/1] and received funding from the European Union's Horizon 2020 research and innovation programme [grant agreement No 668119, project “IDentIFY”]

PY - 2017/12

Y1 - 2017/12

N2 - PurposeFast Field-Cycling (FFC) MRI is a novel technology that allows varying the main magnetic field B0 during the pulse sequence, from the nominal field (usually hundreds of millitesla) down to Earth's field or below. This technique uses resistive magnets powered by fast amplifiers. One of the challenges with this method is to stabilise the magnetic field during the acquisition of the NMR signal. Indeed, a typical consequence of field instability is small, random phase variations between each line of k-space resulting in artefacts, similar to those which occur due to homogeneous motion but harder to correct as no assumption can be made about the phase error, which appears completely random. Here we propose an algorithm that can correct for the random phase variations induced by field instabilities without prior knowledge about the phase error.MethodsThe algorithm exploits the fact that ghosts caused by field instability manifest in image regions which should be signal free. The algorithm minimises the signal in the background by finding an optimum phase correction for each line of k-space and repeats the operation until the result converges, leaving the background free of signal.ConclusionWe showed the conditions for which the algorithm is robust and successfully applied it on images acquired on FFC-MRI scanners. The same algorithm can be used for various applications other than Fast Field-Cycling MRI.

AB - PurposeFast Field-Cycling (FFC) MRI is a novel technology that allows varying the main magnetic field B0 during the pulse sequence, from the nominal field (usually hundreds of millitesla) down to Earth's field or below. This technique uses resistive magnets powered by fast amplifiers. One of the challenges with this method is to stabilise the magnetic field during the acquisition of the NMR signal. Indeed, a typical consequence of field instability is small, random phase variations between each line of k-space resulting in artefacts, similar to those which occur due to homogeneous motion but harder to correct as no assumption can be made about the phase error, which appears completely random. Here we propose an algorithm that can correct for the random phase variations induced by field instabilities without prior knowledge about the phase error.MethodsThe algorithm exploits the fact that ghosts caused by field instability manifest in image regions which should be signal free. The algorithm minimises the signal in the background by finding an optimum phase correction for each line of k-space and repeats the operation until the result converges, leaving the background free of signal.ConclusionWe showed the conditions for which the algorithm is robust and successfully applied it on images acquired on FFC-MRI scanners. The same algorithm can be used for various applications other than Fast Field-Cycling MRI.

KW - Fast field-cycling MRI

KW - Phase encode artefact

KW - Correction algorithm

KW - Post-processing

U2 - 10.1016/j.mri.2017.07.023

DO - 10.1016/j.mri.2017.07.023

M3 - Article

VL - 44

SP - 55

EP - 59

JO - Magnetic Resonance Imaging

JF - Magnetic Resonance Imaging

SN - 0730-725X

ER -