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Effect of inaccurate b-values from imaging gradients on intravoxel incoherent motion

Rashid, Ivan A LU orcid ; Szczepankiewicz, Filip LU orcid ; Gunnlaugsson, Adalsteinn LU ; Olsson, Lars E LU orcid and Brynolfsson, Patrik LU orcid (2025) In Magnetic Resonance in Medicine p.1-15
Abstract

PURPOSE: Neglecting imaging gradients in b-value calculations has been a documented issue for decades and remains unaccounted for in the current postprocessing pipelines. This omission may introduce inaccuracies that propagate into diffusion parameter estimates, such as in ADC and DTI analysis. Because intravoxel incoherent motion (IVIM) makes use of low b-values, these inaccuracies may be of greater importance. This study examines the impact of biased b-values on IVIM analysis in simulations and in vivo.

METHODS: In simulations, b-values were calculated for two pulsed gradient spin-echo sequence designs: one with large cross-terms between imaging and diffusion gradients, and one with minimal cross-terms. Biased and unbiased... (More)

PURPOSE: Neglecting imaging gradients in b-value calculations has been a documented issue for decades and remains unaccounted for in the current postprocessing pipelines. This omission may introduce inaccuracies that propagate into diffusion parameter estimates, such as in ADC and DTI analysis. Because intravoxel incoherent motion (IVIM) makes use of low b-values, these inaccuracies may be of greater importance. This study examines the impact of biased b-values on IVIM analysis in simulations and in vivo.

METHODS: In simulations, b-values were calculated for two pulsed gradient spin-echo sequence designs: one with large cross-terms between imaging and diffusion gradients, and one with minimal cross-terms. Biased and unbiased b-values were calculated from sequences with 200 diffusion directions. These b-values were used to generate IVIM signal curves for parameter estimation. Simulations were repeated with varying in-plane resolutions (1-4 mm) and slice thicknesses (2-10 mm). Additionally, 15 prostate exams were analyzed with scanner-provided b-values and actual b-values derived from the gradient waveforms of the full pulse sequence.

RESULTS: The magnitude and direction of errors in IVIM parameters depended on pulse sequence design. Errors persisted until the full contribution of imaging gradients was considered. Errors in the in vivo data were coherent with the simulations, showing errors of -0.7% in f, 0.8 μm2/ms in D*, and 0.07 μm2/ms in D.

CONCLUSION: Ignoring imaging gradients in b-value calculations introduces unnecessary inaccuracies, making IVIM results spurious and highly dependent on specific pulse sequence design and imaging parameters. These inaccuracies can be corrected by adjusting the b-value calculations, without additional measurements.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
epub
subject
in
Magnetic Resonance in Medicine
pages
1 - 15
publisher
John Wiley & Sons Inc.
external identifiers
  • pmid:40457638
  • scopus:105007420037
ISSN
1522-2594
DOI
10.1002/mrm.30579
language
English
LU publication?
yes
additional info
© 2025 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.
id
78ba43be-e4a0-433c-b5c5-8a822acc1b36
date added to LUP
2025-06-13 14:07:13
date last changed
2025-07-26 07:54:50
@article{78ba43be-e4a0-433c-b5c5-8a822acc1b36,
  abstract     = {{<p>PURPOSE: Neglecting imaging gradients in b-value calculations has been a documented issue for decades and remains unaccounted for in the current postprocessing pipelines. This omission may introduce inaccuracies that propagate into diffusion parameter estimates, such as in ADC and DTI analysis. Because intravoxel incoherent motion (IVIM) makes use of low b-values, these inaccuracies may be of greater importance. This study examines the impact of biased b-values on IVIM analysis in simulations and in vivo.</p><p>METHODS: In simulations, b-values were calculated for two pulsed gradient spin-echo sequence designs: one with large cross-terms between imaging and diffusion gradients, and one with minimal cross-terms. Biased and unbiased b-values were calculated from sequences with 200 diffusion directions. These b-values were used to generate IVIM signal curves for parameter estimation. Simulations were repeated with varying in-plane resolutions (1-4 mm) and slice thicknesses (2-10 mm). Additionally, 15 prostate exams were analyzed with scanner-provided b-values and actual b-values derived from the gradient waveforms of the full pulse sequence.</p><p>RESULTS: The magnitude and direction of errors in IVIM parameters depended on pulse sequence design. Errors persisted until the full contribution of imaging gradients was considered. Errors in the in vivo data were coherent with the simulations, showing errors of -0.7% in f, 0.8 μm2/ms in D*, and 0.07 μm2/ms in D.</p><p>CONCLUSION: Ignoring imaging gradients in b-value calculations introduces unnecessary inaccuracies, making IVIM results spurious and highly dependent on specific pulse sequence design and imaging parameters. These inaccuracies can be corrected by adjusting the b-value calculations, without additional measurements.</p>}},
  author       = {{Rashid, Ivan A and Szczepankiewicz, Filip and Gunnlaugsson, Adalsteinn and Olsson, Lars E and Brynolfsson, Patrik}},
  issn         = {{1522-2594}},
  language     = {{eng}},
  month        = {{06}},
  pages        = {{1--15}},
  publisher    = {{John Wiley & Sons Inc.}},
  series       = {{Magnetic Resonance in Medicine}},
  title        = {{Effect of inaccurate b-values from imaging gradients on intravoxel incoherent motion}},
  url          = {{http://dx.doi.org/10.1002/mrm.30579}},
  doi          = {{10.1002/mrm.30579}},
  year         = {{2025}},
}