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Concomitant Gradient Effects Across Field Strengths and Gradient Amplitudes : Improved Estimation of Errors and Correction of Concomitant Dephasing and Diffusion Weighting

Olsson, Viktor ; Mortensen, Felix LU ; Ljungberg, Emil LU orcid ; Testud, Frederik LU orcid ; Wirestam, Ronnie LU orcid ; Molendowska, Malwina LU and Szczepankiewicz, Filip LU orcid (2026) In Magnetic Resonance in Medicine 96(3). p.1178-1191
Abstract

PURPOSE: Deleterious effects from concomitant gradients are amplified at lower field strengths and stronger gradients. We aimed to show the signal errors caused by concomitant gradients across a wide range of hardware configurations and propose corrections that can be applied during experimental design and analysis.

THEORY AND METHODS: We derived a compact but accurate expression for concomitant gradients and simulated the associated signal bias across field strengths (0.03-7 T) and gradient amplitudes (20-600 mT/m) for asymmetric Maxwell-compensated diffusion encoding gradient waveforms. Bias was assigned to "concomitant dephasing" or "concomitant diffusion weighting." Concomitant dephasing was reduced by waveform correction that... (More)

PURPOSE: Deleterious effects from concomitant gradients are amplified at lower field strengths and stronger gradients. We aimed to show the signal errors caused by concomitant gradients across a wide range of hardware configurations and propose corrections that can be applied during experimental design and analysis.

THEORY AND METHODS: We derived a compact but accurate expression for concomitant gradients and simulated the associated signal bias across field strengths (0.03-7 T) and gradient amplitudes (20-600 mT/m) for asymmetric Maxwell-compensated diffusion encoding gradient waveforms. Bias was assigned to "concomitant dephasing" or "concomitant diffusion weighting." Concomitant dephasing was reduced by waveform correction that was deployed in the design stage. Concomitant diffusion weighting could be accounted for by using the actual gradient waveform during analysis.

RESULTS: Concomitant dephasing was caused by loss of Maxwell compensation during waveform resampling, with signal errors up to 100%, especially at low B0 and high gmax. Our waveform correction yielded a categorical improvement to signal accuracy, reducing bias to < 1% for most systems. However, bias at extreme B0-gmax-combinations remained > 1% (e.g., B0 = 3 T and gmax = 600 mT/m). Concomitant diffusion weighting caused biases above 1% at across all simulated MRI systems.

CONCLUSION: Concomitant gradients have a relevant impact on signal accuracy, especially at low fields and ultra-strong gradients. Concomitant dephasing must be considered for asymmetric waveforms, but can be largely suppressed by our correction method. Concomitant diffusion weighting is always present, regardless of waveform symmetry, but has a smaller impact and can be accounted for in the analysis.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Diffusion Magnetic Resonance Imaging/methods, Algorithms, Humans, Image Processing, Computer-Assisted/methods, Computer Simulation, Phantoms, Imaging, Brain/diagnostic imaging, Reproducibility of Results, Artifacts, Signal Processing, Computer-Assisted
in
Magnetic Resonance in Medicine
volume
96
issue
3
pages
1178 - 1191
publisher
John Wiley & Sons Inc.
external identifiers
  • scopus:105041622352
  • pmid:42277621
ISSN
1522-2594
DOI
10.1002/mrm.70422
language
English
LU publication?
yes
additional info
© 2026 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.
id
9b78e91d-5f59-47ac-89d1-660e8b951b92
date added to LUP
2026-09-02 09:07:28
date last changed
2026-09-17 04:45:53
@article{9b78e91d-5f59-47ac-89d1-660e8b951b92,
  abstract     = {{<p>PURPOSE: Deleterious effects from concomitant gradients are amplified at lower field strengths and stronger gradients. We aimed to show the signal errors caused by concomitant gradients across a wide range of hardware configurations and propose corrections that can be applied during experimental design and analysis.</p><p>THEORY AND METHODS: We derived a compact but accurate expression for concomitant gradients and simulated the associated signal bias across field strengths (0.03-7 T) and gradient amplitudes (20-600 mT/m) for asymmetric Maxwell-compensated diffusion encoding gradient waveforms. Bias was assigned to "concomitant dephasing" or "concomitant diffusion weighting." Concomitant dephasing was reduced by waveform correction that was deployed in the design stage. Concomitant diffusion weighting could be accounted for by using the actual gradient waveform during analysis.</p><p>RESULTS: Concomitant dephasing was caused by loss of Maxwell compensation during waveform resampling, with signal errors up to 100%, especially at low B0 and high gmax. Our waveform correction yielded a categorical improvement to signal accuracy, reducing bias to &lt; 1% for most systems. However, bias at extreme B0-gmax-combinations remained &gt; 1% (e.g., B0 = 3 T and gmax = 600 mT/m). Concomitant diffusion weighting caused biases above 1% at across all simulated MRI systems.</p><p>CONCLUSION: Concomitant gradients have a relevant impact on signal accuracy, especially at low fields and ultra-strong gradients. Concomitant dephasing must be considered for asymmetric waveforms, but can be largely suppressed by our correction method. Concomitant diffusion weighting is always present, regardless of waveform symmetry, but has a smaller impact and can be accounted for in the analysis.</p>}},
  author       = {{Olsson, Viktor and Mortensen, Felix and Ljungberg, Emil and Testud, Frederik and Wirestam, Ronnie and Molendowska, Malwina and Szczepankiewicz, Filip}},
  issn         = {{1522-2594}},
  keywords     = {{Diffusion Magnetic Resonance Imaging/methods; Algorithms; Humans; Image Processing, Computer-Assisted/methods; Computer Simulation; Phantoms, Imaging; Brain/diagnostic imaging; Reproducibility of Results; Artifacts; Signal Processing, Computer-Assisted}},
  language     = {{eng}},
  number       = {{3}},
  pages        = {{1178--1191}},
  publisher    = {{John Wiley & Sons Inc.}},
  series       = {{Magnetic Resonance in Medicine}},
  title        = {{Concomitant Gradient Effects Across Field Strengths and Gradient Amplitudes : Improved Estimation of Errors and Correction of Concomitant Dephasing and Diffusion Weighting}},
  url          = {{http://dx.doi.org/10.1002/mrm.70422}},
  doi          = {{10.1002/mrm.70422}},
  volume       = {{96}},
  year         = {{2026}},
}