Model-based multi-parameter mapping

Balbastre, Yaël; Brudfors, Mikael; Azzarito, Michela; Lambert, Christian; Callaghan, Martina F.; Ashburner, John

doi:10.1016/j.media.2021.102149

Cited by 4 publications

(3 citation statements)

References 75 publications

(100 reference statements)

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“…We used a mono‐exponential fit method to calculate the R2*. Future advanced models incorporating the non‐Gaussian noise models could help to get more accurate R2* mapping (Balbastre et al, 2021 ). Third, our current study focused on healthy older participants 60–80 years of age and younger controls 21–30 years of age.…”

Section: Discussionmentioning

confidence: 99%

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease

Lin

Shahid

Hone‐Blanchet

et al. 2023

Human Brain Mapping

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While iron over‐accumulation has been reported in late stage Alzheimer's disease (AD), whether this occurs early in the asymptomatic stage of AD remains unknown. We aimed to assess brain iron levels in asymptomatic AD using quantitative MR relaxometry of effective transverse relaxation rate (R2*) and longitudinal relaxation rate (R1), and recruited 118 participants comprised of three groups including healthy young participants, and cognitively normal older individuals without or with positive AD biomarkers based on cerebrospinal fluid (CSF) proteomics analysis. Compared with the healthy young group, increased R2* was found in widespread cortical and subcortical regions in the older groups. Further, significantly higher levels of R2* were found in the cognitively normal older subjects with positive CSF AD biomarker (i.e., asymptomatic AD) compared with those with negative AD biomarker in subcortical regions including the left and right caudate, left and right putamen, and left and right globus pallidus ( p < .05 for all regions), suggesting increased iron content in these regions. Subcortical R2* of some regions was found to significantly correlate with CSF AD biomarkers and neuropsychological assessments of visuospatial functions. In conclusion, R2* could be a valuable biomarker for studying early pathophysiological changes in AD.

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Section: Discussionmentioning

confidence: 99%

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease

Lin

Shahid

Hone‐Blanchet

et al. 2023

Human Brain Mapping

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“…Furthermore, rigid registration could be interleaved with model fitting 12 to reach a better global optimum. Finally, the generative model could naturally be integrated with any fitting approach that defines a joint probability over all acquired data, such as Balbastre et al 13 in the context of MPM.…”

Section: Discussionmentioning

confidence: 99%

“…We therefore replace the Gauss-Newton Hessian with the more robust preconditioner: ) which has been shown to yield monotonic convergence. 13 The inversion in equation (A9) is performed with a full multi-grid solver that leverages the sparsity and structure of the preconditioner. 20 Finally, a global scaling field s = exp z, applied to both the sensitivities (s kn ← s kn ∕s n ) and mean image (r n ← s n r n ), ensures that the product s kn r n is unchanged.…”

Section: F I G U R Ementioning

confidence: 99%

Correcting inter‐scan motion artifacts in quantitative R₁ mapping at 7T

Balbastre

Aghaeifar

Corbin

et al. 2022

Magnetic Resonance in Med

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Inter-scan motion is a substantial source of error in R 1 estimation methods based on multiple volumes, for example, variable flip angle (VFA), and can be expected to increase at 7T where B 1 fields are more inhomogeneous. The established correction scheme does not translate to 7T since it requires a body coil reference. Here we introduce two alternatives that outperform the established method. Since they compute relative sensitivities they do not require body coil images. Theory:The proposed methods use coil-combined magnitude images to obtain the relative coil sensitivities. The first method efficiently computes the relative sensitivities via a simple ratio; the second by fitting a more sophisticated generative model.Methods: R 1 maps were computed using the VFA approach. Multiple datasets were acquired at 3T and 7T, with and without motion between the acquisition of the VFA volumes. R 1 maps were constructed without correction, with the proposed corrections, and (at 3T) with the previously established correction scheme. The effect of the greater inhomogeneity in the transmit field at 7T was also explored by acquiring B + 1 maps at each position. Results: At 3T, the proposed methods outperform the baseline method.Inter-scan motion artifacts were also reduced at 7T. However, at 7T reproducibility only converged on that of the no motion condition if position-specific transmit field effects were also incorporated. Conclusion:The proposed methods simplify inter-scan motion correction of R 1 maps and are applicable at both 3T and 7T, where a body coil is typically not available. The open-source code for all methods is made publicly available.

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Multiparameter Mapping

Polzehl,

Tabelow

2023

Use R!

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Model-based multi-parameter mapping

Abstract: Highlights Model-based estimation of quantitative multi-parameter maps. Maximum-likelihood or Maximum a posteriori solutions. Embedded denoising using a joint total-variation prior. Stable second-order solver using a novel approximate Hessian.

Cited by 4 publications

References 75 publications

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease

Correcting inter‐scan motion artifacts in quantitative R₁ mapping at 7T

Multiparameter Mapping

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Model-based multi-parameter mapping

Abstract: Highlights Model-based estimation of quantitative multi-parameter maps. Maximum-likelihood or Maximum a posteriori solutions. Embedded denoising using a joint total-variation prior. Stable second-order solver using a novel approximate Hessian.

Cited by 4 publications

References 75 publications

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease

Magnetic resonance evidence of increased iron content in subcortical brain regions in asymptomatic Alzheimer's disease

Correcting inter‐scan motion artifacts in quantitative R1 mapping at 7T

Multiparameter Mapping

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Product

Resources

About

Correcting inter‐scan motion artifacts in quantitative R₁ mapping at 7T