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

Mchinda, Samira; Varma, Gopal; Prevost, Valentin H.; Troter, Arnaud Le; Rapacchi, Stanislas; Guye, Maxime; Pelletier, Jean; Ranjeva, Jean‐Philippe; Alsop, David C.; Duhamel, Guillaume; Girard, Olivier

doi:10.1002/mrm.26907

Cited by 38 publications

(127 citation statements)

References 30 publications

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“…Histological research has revealed that myelination continues throughout adolescence (Benes, ; Yakovlev & Lecours, ), thus it remains possible that MT and ihMT measures applied to date have lacked the sensitivity required to describe myelination during this period. Optimizations to ihMT methods have been identified which may enable future studies to address myelination trajectories during adolescence with greater clarity (McHinda et al, ; Prevost et al, ). When considered together, our VF m and qihMT findings suggest that myelin sheaths may be incorporating more water between a relatively stable number of wrapped membranes during adolescence.…”

Section: Discussionmentioning

confidence: 99%

A multiparametric analysis of white matter maturation during late childhood and adolescence

Geeraert

Lebel

2019

Human Brain Mapping

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White matter development has been well described using diffusion tensor imaging (DTI), but the microstructural processes driving development remain unclear due to methodological limitations. Here, using neurite orientation dispersion and density imaging (NODDI), inhomogeneous magnetization transfer (ihMT), and multicomponent driven equilibrium single‐pulse observation of T1/T2 (mcDESPOT), we describe white matter development at the microstructural level in a longitudinal cohort of healthy 6–15 year olds. We evaluated age and gender‐related trends in fractional anisotropy (FA), mean diffusivity (MD), neurite density index (NDI), orientation dispersion index (ODI), quantitative ihMT (qihMT), myelin volume fraction (VFm), and g‐ratio. We found age‐related increases of VFm in most regions, showing ongoing myelination in vivo during late childhood and adolescence for the first time. No relationship was observed between qihMT and age, suggesting myelin volume increases are driven by increased water content. Age‐related increases were observed for NDI, suggesting axonal packing is also occurring during this time. g‐ratio decreased with age in the uncinate fasciculus, implying changes in communication efficiency are ongoing in this region. FA increased and MD decreased with age in most regions. Gender effects were present in the left cingulum for FA, and an age‐by‐gender interaction was found for MD in the left uncinate fasciculus. These findings suggest that FA and MD remain useful markers of gender‐related processes, and gender differences are likely driven by factors other than myelin. We conclude that white matter development during late childhood and adolescence is driven by a combination of axonal packing and myelin volume increases.

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Section: Discussionmentioning

confidence: 99%

A multiparametric analysis of white matter maturation during late childhood and adolescence

Geeraert

Lebel

2019

Human Brain Mapping

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“…It is worth noting that this choice of slice thickness (10 mm) was driven by the important need of SNR in the ihMT acquisition and was applied to DTI to ensure the same PVE‐induced contamination. Current strategies developed to enhance the ihMT signal will greatly help to handle these issues in future studies.…”

Section: Discussionmentioning

confidence: 99%

“…7 T) should be feasible in principle as long as the RF energy deposition is maintained within regulatory constraints. In this perspective, recent strategies aimed at reducing the RF demand to optimize the ihMTR are of great utility …”

Section: Discussionmentioning

confidence: 99%

“…Hence, thanks to its long T 1D , the dipolar order contribution of the myelinated structures can be isolated from the broad MT signal, giving rise to an enhanced myelinated tissue contrast relative to conventional MT . Although extensive work is still ongoing for the full characterization of this technique, it has already been used to assess brain and SC tissue demyelination in normal aging and multiple sclerosis . It has not been applied in ALS so far, and could provide new insights into the pathophysiology of ALS.…”

Section: Introductionmentioning

confidence: 99%

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Region‐specific impairment of the cervical spinal cord (SC) in amyotrophic lateral sclerosis: A preliminary study using SC templates and quantitative MRI (diffusion tensor imaging/inhomogeneous magnetization transfer)

et al. 2017

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In this preliminary study, our objective was to investigate the potential of high-resolution anatomical imaging, diffusion tensor imaging (DTI) and conventional/inhomogeneous magnetization transfer imaging [magnetization transfer (MT)/inhomogeneous magnetization transfer (ihMT)] at 3 T, analyzed with template-extracted regions of interest, to measure the atrophy and structural changes of white (WM) and gray (GM) matter spinal cord (SC) occurring in patients with amyotrophic lateral sclerosis (ALS). Ten patients with ALS and 20 age-matched healthy controls were recruited. SC GM and WM areas were automatically segmented using dedicated templates. Atrophy indices were evaluated from T *-weighted images at each vertebral level from cervical C1 to C6. DTI and ihMT metrics were quantified within the corticospinal tract (CST), posterior sensory tract (PST) and anterior GM (aGM) horns at the C2 and C5 levels. Clinical disabilities of patients with ALS were evaluated using the Revised ALS Functional Rating Scale, upper motor neuron (UMN) and Medical Research Council scorings, and correlated with MR metrics. Compared with healthy controls, GM and WM atrophy was observed in patients with ALS, especially at lower cervical levels, where a strong correlation was also observed between GM atrophy and the UMN score (R = -0.75, p = 0.05 at C6). Interestingly, a significant decrease in ihMT ratio was found in all regions of interest (p < 0.0008), fractional anisotropy (FA) and MT ratios decreased significantly in CST, especially at C5 (p < 0.005), and λ (axial diffusivity) decreased significantly in CST (p = 0.0004) and PST (p = 0.003) at C2. Strong correlations between MRI metrics and clinical scores were also found (0.47 < |R| < 0.87, p < 0.05). Altogether, these preliminary results suggest that high-resolution anatomical imaging and ihMT imaging, in addition to DTI, are valuable for the characterization of SC tissue impairment in ALS. In this study, in addition to an important SC WM demyelination, we also observed, for the first time in ALS, impairments of cervical aGM.

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“…In the healthy population, tissue type distributions resemble those obtained with a state‐of‐the‐art ihMT protocol (see Figure of Mchinda et al) with 2 distinct peaks for WM and cGM, and a higher BPF in the dGM structures, e.g., the thalamus, compared with cGM. The clearer separation between distributions provided by ihMT points toward the higher sensitivity of ihMT to myelin than conventional MT; however, the quantitative nature of the BPF may be advantageous when using such a parameter to quantify changes in disease.…”

Section: Discussionmentioning

confidence: 53%

Fast bound pool fraction mapping via steady‐state magnetization transfer saturation using single‐shot EPI

Battiston

Schneider

Grussu

et al. 2019

Magnetic Resonance in Med

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Purpose:To enable clinical applications of quantitative magnetization transfer (qMT) imaging by developing a fast method to map one of its fundamental model parameters, the bound pool fraction (BPF), in the human brain. Theory and Methods: The theory of steady-state MT in the fast-exchange approximation is used to provide measurements of BPF, and bound pool transverse relaxation time (T B 2 ). A sequence that allows sampling of the signal during steady-state MT saturation is used to perform BPF mapping with a 10-min-long fully echo planar imaging-based MRI protocol, including inversion recovery T 1 mapping and B 1 error mapping. The approach is applied in 6 healthy subjects and 1 multiple sclerosis patient, and validated against a single-slice full qMT reference acquisition. Results: BPF measurements are in agreement with literature values using offresonance MT, with average BPF of 0.114(0.100-0.128) in white matter and 0.068(0.054-0.085) in gray matter. Median voxel-wise percentage error compared with standard single slice qMT is 4.6%. Slope and intercept of linear regression between new and reference BPF are 0.83(0.81-0.85) and 0.013(0.11-0.16). Bland-Altman plot mean bias is 0.005. In the multiple sclerosis case, the BPF is sensitive to pathological changes in lesions. Conclusion: The method developed provides accurate BPF estimates and enables shorter scan time compared with currently available approaches, demonstrating the potential of bringing myelin sensitive measurement closer to the clinic. K E Y W O R D S 2-pool model, bound pool fraction, EPI, magnetization transfer, myelin, quantitative steady-state 1026 | BATTISTON eT Al.

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

Cited by 38 publications

References 30 publications

A multiparametric analysis of white matter maturation during late childhood and adolescence

A multiparametric analysis of white matter maturation during late childhood and adolescence

Region‐specific impairment of the cervical spinal cord (SC) in amyotrophic lateral sclerosis: A preliminary study using SC templates and quantitative MRI (diffusion tensor imaging/inhomogeneous magnetization transfer)

Fast bound pool fraction mapping via steady‐state magnetization transfer saturation using single‐shot EPI

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