Imperfect spoiling in variable flip angle T<sub>1</sub> mapping at 7T: Quantifying and minimizing impact

Corbin, Nadège; Callaghan, Martina F.

doi:10.1002/mrm.28720

Cited by 19 publications

(19 citation statements)

References 45 publications

(56 reference statements)

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“…The structural MRI data were processed for each participant using the hMRI toolbox (Tabelow et al, 2019) within SPM12. The default toolbox configuration settings were used, with the exception that correction for imperfect spoiling was additionally enabled (Corbin and Callaghan, 2021). The output MT saturation map, used as the anatomically faithful structural image, quantified the degree of saturation of the steady state signal induced by the application of the off-resonance pre-pulse, having accounted for spatially varying T1 times and RF field inhomogeneity (Helms et al, 2008; Weiskopf et al, 2013).…”

Section: Methodsmentioning

confidence: 99%

Reducing susceptibility distortion related image blurring in diffusion MRI EPI data

Clark

Callaghan

Weiskopf

et al. 2021

Preprint

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Diffusion magnetic resonance imaging (MRI) is an increasingly popular technique in basic and clinical neuroscience. One promising application is to combine diffusion MRI with myelin maps from complementary MRI techniques such as multi-parameter mapping (MPM) to produce g-ratio maps that represent the relative myelination of axons and predict their conduction velocity. Statistical Parametric Mapping (SPM) can process both diffusion data and MPMs, making SPM the only widely accessible software that contains all the processing steps required to perform group analyses of g-ratio data in a common space. However, limitations have been identified in its method for reducing susceptibility-related distortion in diffusion data. More generally, susceptibility-related image distortion is often corrected by combining oppositely phase-encoded images (blip-up and blip-down) using the arithmetic mean (AM), however, this can lead to blurred images. In this study we sought to (1) improve the susceptibility-related distortion correction for diffusion MRI data in SPM; (2) deploy an alternative approach to the AM to reduce image blurring in diffusion MRI data when combining blip-up and blip-down EPI data after susceptibility-related distortion correction; and (3) assess the benefits of these changes for g-ratio mapping. We found that the new processing pipeline, called consecutive HySCO, improved distortion correction when compared to the standard approach in the ACID toolbox for SPM. Moreover, using a weighted average (WA) method to combine the distortion corrected data from each phase-encoding polarity achieved greater overlap of diffusion and more anatomically faithful structural white matter probability maps derived from minimally distorted multi-parameter maps as compared to the AM. Third, we showed that the consecutive HySCO WA performed better than the AM method when combined with multi-parameter maps to perform g-ratio mapping. These improvements mean that researchers can conveniently access a wide range of diffusion-related analysis methods within one framework because they are now available within the open-source ACID toolbox as part of SPM, which can be easily combined with other SPM toolboxes, such as the hMRI toolbox, to facilitate computation of myelin biomarkers that are necessary for g-ratio mapping.

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Section: Methodsmentioning

confidence: 99%

Reducing susceptibility distortion related image blurring in diffusion MRI EPI data

Clark

Callaghan

Weiskopf

et al. 2021

Preprint

Self Cite

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show abstract

“…The structural MRI data were processed for each participant using the hMRI toolbox (Tabelow et al, 2019) within SPM12. The default toolbox configuration settings were used, with the exception that correction for imperfect spoiling was additionally enabled (Corbin and Callaghan, 2021). The output MT saturation map, used as the anatomically faithful structural image, quantified the degree of saturation of the steady state signal induced by the application of the off-resonance prepulse, having accounted for spatially varying T 1 times and RF field inhomogeneity (Helms et al, 2008;Weiskopf et al, 2013).…”

Section: Structural Mri Data Pre-processingmentioning

confidence: 99%

Reducing Susceptibility Distortion Related Image Blurring in Diffusion MRI EPI Data

et al. 2021

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Diffusion magnetic resonance imaging (MRI) is an increasingly popular technique in basic and clinical neuroscience. One promising application is to combine diffusion MRI with myelin maps from complementary MRI techniques such as multi-parameter mapping (MPM) to produce g-ratio maps that represent the relative myelination of axons and predict their conduction velocity. Statistical Parametric Mapping (SPM) can process both diffusion data and MPMs, making SPM the only widely accessible software that contains all the processing steps required to perform group analyses of g-ratio data in a common space. However, limitations have been identified in its method for reducing susceptibility-related distortion in diffusion data. More generally, susceptibility-related image distortion is often corrected by combining reverse phase-encoded images (blip-up and blip-down) using the arithmetic mean (AM), however, this can lead to blurred images. In this study we sought to (1) improve the susceptibility-related distortion correction for diffusion MRI data in SPM; (2) deploy an alternative approach to the AM to reduce image blurring in diffusion MRI data when combining blip-up and blip-down EPI data after susceptibility-related distortion correction; and (3) assess the benefits of these changes for g-ratio mapping. We found that the new processing pipeline, called consecutive Hyperelastic Susceptibility Artefact Correction (HySCO) improved distortion correction when compared to the standard approach in the ACID toolbox for SPM. Moreover, using a weighted average (WA) method to combine the distortion corrected data from each phase-encoding polarity achieved greater overlap of diffusion and more anatomically faithful structural white matter probability maps derived from minimally distorted multi-parameter maps as compared to the AM. Third, we showed that the consecutive HySCO WA performed better than the AM method when combined with multi-parameter maps to perform g-ratio mapping. These improvements mean that researchers can conveniently access a wide range of diffusion-related analysis methods within one framework because they are now available within the open-source ACID toolbox as part of SPM, which can be easily combined with other SPM toolboxes, such as the hMRI toolbox, to facilitate computation of myelin biomarkers that are necessary for g-ratio mapping.

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“…As recommended for the preprocessing stream, we used highly accurate and precise RF transmit field maps with a total error of less than 3% (Lutti et al, 2010(Lutti et al, , 2012 and corrected for imperfect RF spoiling. The previous effects lead to deviations from the Ernst signal equation underlying the R1 estimation and imprecisions in their correction may thus lead to inaccuracies (Corbin & Callaghan, 2021;Yarnykh, 2010). For example, even small deviations of 3% in the RF transmit field mapping can cause errors of up to 6% in the R1 maps due to the quadratic dependence of the estimated R1 on the local flip angle (Weiskopf et al, 2011).…”

Section: Potential Causes Of Variations In Parameter Mapsmentioning

confidence: 99%

Reliability of quantitative multiparameter maps is high for MT and PD but attenuated for R1 and R2* in healthy young adults

Wenger

Polk

Kleemeyer

et al. 2021

Preprint

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We investigate the reliability of individual differences of four quantities measured by magnetic resonance imaging based multiparameter mapping (MPM): magnetization transfer (MT), proton density (PD), longitudinal relaxation rate (R1), and effective transverse relaxation rate (R2*). A total of four MPM datasets, two on each of two consecutive days, were acquired in healthy young adults. On Day 1, no repositioning occurred; on Day 2, participants were repositioned between MPM datasets. Using intra-class correlation effect decomposition (ICED), we assessed the contributions of session-specific, day-specific, and residual sources of measurement error. For whole-brain gray and white matter, all four MPM parameters showed high reproducibility and high reliability, as indexed by the coefficient of variation (CoV) and the intra-class correlation (ICC). However, MT, PD, R1, and R2* differed markedly in the extent to which reliability varied across brain regions. MT and PD showed high reliability in almost all regions. In contrast, R1 and R2* showed low reliability in some regions outside the basal ganglia, such that the sum of the measurement error estimates in our structural equation model was higher than estimates of between-person differences. In sum, in this sample of healthy young adults, the four MPM parameters showed very little variability over four measurements over two days but differed in how well they could assess between-person differences. We conclude that R1 and R2* might carry only limited person-specific information in samples of healthy young adults, and, by implication, might be of restricted utility for studying associations to between-person differences in behavior.

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Imperfect spoiling in variable flip angle T₁ mapping at 7T: Quantifying and minimizing impact

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 19 publications

References 45 publications

Reducing susceptibility distortion related image blurring in diffusion MRI EPI data

Reducing susceptibility distortion related image blurring in diffusion MRI EPI data

Reducing Susceptibility Distortion Related Image Blurring in Diffusion MRI EPI Data

Reliability of quantitative multiparameter maps is high for MT and PD but attenuated for R1 and R2* in healthy young adults

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Imperfect spoiling in variable flip angle T1 mapping at 7T: Quantifying and minimizing impact

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 19 publications

References 45 publications

Reducing susceptibility distortion related image blurring in diffusion MRI EPI data

Reducing susceptibility distortion related image blurring in diffusion MRI EPI data

Reducing Susceptibility Distortion Related Image Blurring in Diffusion MRI EPI Data

Reliability of quantitative multiparameter maps is high for MT and PD but attenuated for R1 and R2* in healthy young adults

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Imperfect spoiling in variable flip angle T₁ mapping at 7T: Quantifying and minimizing impact