Magnetization transfer from inhomogeneously broadened lines (ihMT): Improved imaging strategy for spinal cord applications

Girard, Olivier; Callot, Virginie; Prevost, Valentin H.; Robert, Benjamin; Taso, Manuel; Ribeiro, Guilherme Aramizo; Varma, Gopal; Rangwala, Novena; Alsop, David C.; Duhamel, Guillaume

doi:10.1002/mrm.26134

Cited by 27 publications

(51 citation statements)

References 23 publications

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“…Absolute ihMTR values in mouse brain and spinal cord WM measured in this study were approximately 1.5–2 times smaller than those reported in humans at 1.5 T in similar structures . The low resolution used in this study, and the consequential partial volume effects, might have led to underestimated values, thus explaining, at least in part, these differences.…”

Section: Discussioncontrasting

confidence: 67%

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T_1D) filtering

et al. 2017

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A pulsed inhomogeneous magnetization transfer (ihMT)-prepared fast imaging sequence was implemented at 11.75 T for preclinical studies on mouse central nervous system. A strategy based on filtering the ihMT signal originating from short dipolar relaxation time (T ) components is proposed. It involves increasing the repetition time of consecutive radiofrequency (RF) pulses of the dual saturation and allows improved signal specificity for long T myelinated structures. Furthermore, frequency offset, power and timing saturation parameters were adjusted to optimize the ihMT sensitivity. The optimization of the ihMT sensitivity, whilst preserving the strong specificity for the long T component of myelinated tissues, allowed measurements of ihMT ratios on the order of 4-5% in white matter (WM), 2.5% in gray matter (GM) and 1-1.3% in muscle. This led to high relative ihMT contrasts between myelinated tissues and others (~3-4 between WM and muscle, and ≥2 between GM and muscle). Conversely, higher ihMT ratios (~6-7% in WM) could be obtained using minimal T filtering achieved with short saturation pulse repetition time or cosine-modulated pulses for the dual-frequency saturation. This study represents a first stage in the process of validating ihMT as a myelin biomarker by providing optimized ihMT preclinical sequences, directly transposable and applicable to other preclinical magnetic fields and scanners. Finally, ihMT ratios measured in various central nervous system areas are provided for future reference.

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Section: Discussioncontrasting

confidence: 67%

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T_1D) filtering

et al. 2017

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“…k ‐space apodization was also used (Hamming function) to reduce Gibbs artifacts inside the SC. The whole MT/ihMT processing was performed offline with a semi‐automated processing software developed in MATLAB (MATLAB R2012a, MathWorks, Natick, MA, USA).…”

Section: Methodsmentioning

confidence: 99%

Tract-specific and age-related variations of the spinal cord microstructure: a multi-parametric MRI study using diffusion tensor imaging (DTI) and inhomogeneous magnetization transfer (ihMT)

et al. 2016

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Being able to finely characterize the spinal cord (SC) microstructure and its alterations is a key point when investigating neural damage mechanisms encountered in different central nervous system (CNS) pathologies, such as multiple sclerosis, amyotrophic lateral sclerosis or myelopathy. Based on novel methods, including inhomogeneous magnetization transfer (ihMT) and dedicated SC probabilistic atlas post-processing, the present study focuses on the in vivo characterization of the healthy SC tissue in terms of regional microstructure differences between (i) upper and lower cervical vertebral levels and (ii) sensory and motor tracts, as well as differences attributed to normal aging. Forty-eight healthy volunteers aged from 20 to 70 years old were included in the study and scanned at 3 T using axial high-resolution T2 *-w imaging, diffusion tensor imaging (DTI) and ihMT, at two vertebral levels (C2 and C5). A processing pipeline with minimal user intervention, SC segmentation and spatial normalization into a reference space was implemented in order to assess quantitative morphological and structural parameters (cross-sectional areas, scalar DTI and MT/ihMT metrics) in specific white and gray matter regions of interest. The multi-parametric MRI metrics collected allowed upper and lower cervical levels to be distinguished, with higher ihMT ratio (ihMTR), higher axial diffusivity (λ∥ ) and lower radial diffusivity (λ⊥ ) at C2 compared with C5. Significant differences were also observed between white matter fascicles, with higher ihMTR and lower λ∥ in motor tracts compared with posterior sensory tracts. Finally, aging was found to be associated with significant metric alterations (decreased ihMTR and λ∥ ). The methodology proposed here, which can be easily transferred to the clinic, provides new insights for SC characterization. It bears great potential to study focal and diffuse SC damage in neurodegenerative and demyelinating diseases. Copyright © 2016 John Wiley & Sons, Ltd.

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“…This mechanism has been exploited to enhance ihMT signal intensity in a recent preliminary study and subsequently dubbed the boost‐effect. The current study builds on these recent findings with the following aims: to establish a framework to simulate ihMT‐GRE sequences and model ihMT dependence on sequence parameters, to characterize ihMT dependence on the saturation parameters and to optimize the RF energy deposition scheme to achieve the boost‐effect, and to acquire whole brain sensitivity‐boosted ihMT‐GRE images within a clinically compatible scan time at 1.5T.…”

Section: Introductionmentioning

confidence: 99%

Whole brain inhomogeneous magnetization transfer (ihMT) imaging: Sensitivity enhancement within a steady‐state gradient echo sequence

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Varma

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et al. 2017

Magnetic Resonance in Med

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Magnetization transfer from inhomogeneously broadened lines (ihMT): Improved imaging strategy for spinal cord applications

Cited by 27 publications

References 23 publications

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T_1D) filtering

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T_1D) filtering

Tract-specific and age-related variations of the spinal cord microstructure: a multi-parametric MRI study using diffusion tensor imaging (DTI) and inhomogeneous magnetization transfer (ihMT)

Whole brain inhomogeneous magnetization transfer (ihMT) imaging: Sensitivity enhancement within a steady‐state gradient echo sequence

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Magnetization transfer from inhomogeneously broadened lines (ihMT): Improved imaging strategy for spinal cord applications

Cited by 27 publications

References 23 publications

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T1D) filtering

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T1D) filtering

Tract-specific and age-related variations of the spinal cord microstructure: a multi-parametric MRI study using diffusion tensor imaging (DTI) and inhomogeneous magnetization transfer (ihMT)

Whole brain inhomogeneous magnetization transfer (ihMT) imaging: Sensitivity enhancement within a steady‐state gradient echo sequence

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Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T_1D) filtering

Optimization of inhomogeneous magnetization transfer (ihMT) MRI contrast for preclinical studies using dipolar relaxation time (T_1D) filtering