Probing the myelin water compartment with a saturation‐recovery, multi‐echo gradient‐recalled echo sequence

Kleban, Elena; Gowland, Penny; Bowtell, Richard

doi:10.1002/mrm.28695

Cited by 3 publications

(7 citation statements)

References 35 publications

(129 reference statements)

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“…For this purpose, frequency difference mapping (FDM) has been presented recently as a phase-processing technique (Kleban et al, 2021;Sati et al, 2013;Schweser et al, 2011;Tendler & Bowtell, 2019;van Gelderen et al, 2012;Wharton & Bowtell, 2013). FDM is performed by comparing frequency maps acquired at short and long TEs so as to yield local frequency difference values which depend solely upon the underlying tissue microstructure, and in particular upon the local nerve fibre orientation with respect to the applied magnetic field.…”

Section: 2probing Myelin Changes In the Hd Brain With A Multi-echomentioning

confidence: 99%

“…The complex data were reconstructed per receive channel, followed by a complex multiplication of signals acquired with opposite read-gradient-polarities, in order to remove phase shift between adjacent echoes (Kleban et al, 2021). Image-based coil-sensitivityestimation was then used to perform coil combination (Bydder et al, 2002;Roemer et al, 1990).…”

Section: Pre-processing Stepsmentioning

confidence: 99%

“…Image-based coil-sensitivityestimation was then used to perform coil combination (Bydder et al, 2002;Roemer et al, 1990). Frequency difference maps (FDM) were calculated from the phase data to correct for the RF-related phase offsets and the effects of the non-local B0 field inhomogeneities (Kleban et al, 2021;Tendler & Bowtell, 2019). Finally, a 3 rd degree spatial polynomial was fitted to the FDM data at each echo to correct for the residual eddy current effects.…”

Section: Pre-processing Stepsmentioning

confidence: 99%

“…The complex mGRE signal was reconstructed per receive channel and gradient echo at corresponding echo time TE * and can be represented as follows (Sati et al, 2013;Tendler & Bowtell, 2019;Thapaliya et al, 2017;Wharton & Bowtell, 2012;Nam et al 2015aNam et al ,2015bKleban et al 2021…”

Section: A Appendix: Details On Mgre Signal Pre-processingmentioning

confidence: 99%

“…2. Remove phase offsets, particularly those varying between channels (Tendler & Bowtell, 2019;Kleban et al 2021;Bydder et al 2002):…”

Section: A Appendix: Details On Mgre Signal Pre-processingmentioning

confidence: 99%

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Multi-compartment analysis of the complex gradient-echo signal quantifies myelin breakdown in premanifest Huntington’s disease

Casella

Kleban

Rosser

et al. 2021

Preprint

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White matter (WM) alterations have been identified as a relevant pathological feature of Huntington's disease (HD). Increasing evidence suggests that WM changes in this disorder are due to alterations in myelin-associated biological processes. Multi-compartmental analysis of the complex gradient-echo MRI signal evolution in WM has been shown to quantify myelin in vivo, therefore pointing to the potential of this technique for the study of WM myelin changes in health and disease. This study first characterized the reproducibility of metrics derived from the complex multi-echo gradient-recalled echo (mGRE) signal across the corpus callosum in healthy participants, finding highest reproducibility in the posterior callosal segment. Subsequently, the same analysis pipeline was applied in this callosal region in a sample of premanifest HD patients (n = 19) and age, sex and education matched healthy controls (n = 21). In particular, we focused on two myelin-associated derivatives: i. the myelin water signal fraction (fm), a parameter dependent on myelin content; and ii. the difference in frequency between myelin and intra-axonal water pools (Δω), a parameter dependent on the ratio between the inner and the outer axonal radii. fm was found to be lower in HD patients (β = -0.13, p = 0.03), while Δω did not show a group effect. Performance in tests of working memory, executive function, social cognition and movement was also assessed, and a greater age-related decline in executive function was detected in HD patients (β = -0.06, p = 0.006), replicating previous evidence of executive dysfunction in HD. Finally, the correlation between fm, executive function, and proximity to disease onset was explored in patients, and a positive correlation between executive function and fm was detected (r = 0.542; p = 0.02). This study emphasises the potential of complex mGRE signal analysis for aiding understanding of HD pathogenesis and progression. Moreover, expanding on evidence from pathology and animal studies, it provides novel in vivo evidence supporting myelin breakdown as an early feature of HD.

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Section: 2probing Myelin Changes In the Hd Brain With A Multi-echomentioning

confidence: 99%

Section: Pre-processing Stepsmentioning

confidence: 99%

Section: Pre-processing Stepsmentioning

confidence: 99%

Section: A Appendix: Details On Mgre Signal Pre-processingmentioning

confidence: 99%

“…2. Remove phase offsets, particularly those varying between channels (Tendler & Bowtell, 2019;Kleban et al 2021;Bydder et al 2002):…”

Section: A Appendix: Details On Mgre Signal Pre-processingmentioning

confidence: 99%

See 3 more Smart Citations

Multi-compartment analysis of the complex gradient-echo signal quantifies myelin breakdown in premanifest Huntington’s disease

Casella

Kleban

Rosser

et al. 2021

Preprint

Self Cite

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Multi-compartment analysis of the complex gradient-echo signal quantifies myelin breakdown in premanifest Huntington's disease

Casella

Kleban

Rosser

et al. 2021

NeuroImage: Clinical

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Highlights Gradient-echo data were acquired from premanifest HD patients in the callosum at 7 T. Reproducibility of multi-compartment analysis across callosal areas was assessed. Reduced myelin water signal fraction (f m ) in HD patients suggested myelin breakdown. Executive function correlated with callosal f m values in HD patients. The reported approach may aid understanding of HD pathogenesis and progression.

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Fiber-orientation independent component of R2* obtained from single-orientation MRI measurements in simulations and a post-mortem human optic chiasm

Fritz,

Mordhorst,

Ashtarayeh

et al. 2023

Front. Neurosci.

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The effective transverse relaxation rate (R2*) is sensitive to the microstructure of the human brain like the g-ratio which characterises the relative myelination of axons. However, the fibre-orientation dependence of R2* degrades its reproducibility and any microstructural derivative measure. To estimate its orientation-independent part (R2,iso*) from single multi-echo gradient-recalled-echo (meGRE) measurements at arbitrary orientations, a second-order polynomial in time model (hereafter M2) can be used. Its linear time-dependent parameter, β1, can be biophysically related to R2,iso* when neglecting the myelin water (MW) signal in the hollow cylinder fibre model (HCFM). Here, we examined the performance of M2 using experimental and simulated data with variable g-ratio and fibre dispersion. We found that the fitted β1 can estimate R2,iso* using meGRE with long maximum-echo time (TEmax ≈ 54 ms), but not accurately captures its microscopic dependence on the g-ratio (error 84%). We proposed a new heuristic expression for β1 that reduced the error to 12% for ex vivo compartmental R2 values. Using the new expression, we could estimate an MW fraction of 0.14 for fibres with negligible dispersion in a fixed human optic chiasm for the ex vivo compartmental R2 values but not for the in vivo values. M2 and the HCFM-based simulations failed to explain the measured R2*-orientation-dependence around the magic angle for a typical in vivo meGRE protocol (with TEmax ≈ 18 ms). In conclusion, further validation and the development of movement-robust in vivo meGRE protocols with TEmax ≈ 54 ms are required before M2 can be used to estimate R2,iso* in subjects.

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Probing the myelin water compartment with a saturation‐recovery, multi‐echo gradient‐recalled echo sequence

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 3 publications

References 35 publications

Multi-compartment analysis of the complex gradient-echo signal quantifies myelin breakdown in premanifest Huntington’s disease

Multi-compartment analysis of the complex gradient-echo signal quantifies myelin breakdown in premanifest Huntington’s disease

Multi-compartment analysis of the complex gradient-echo signal quantifies myelin breakdown in premanifest Huntington's disease

Fiber-orientation independent component of R2* obtained from single-orientation MRI measurements in simulations and a post-mortem human optic chiasm

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