7T GRE-MRI signal compartments are sensitive to dysplastic tissue in focal epilepsy

Thapaliya, Kiran; Urriola, Javier; Barth, Markus; Reutens, David C.; Bollmann, Steffen; Vegh, Viktor

doi:10.1016/j.mri.2019.05.011

Cited by 12 publications

(11 citation statements)

References 56 publications

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“…34 3D SWI or GRE T 2 *-weighted sequences allow visualization of intracortical signal changes (black line sign), which can improve subtyping of FCD type II. 10,35 Most centers rate 3D T 1 -weighted and FLAIR sequences as most helpful for visualizing and diagnosing FCD because of their high image contrast at 7T; reconstructions in all 3 planes are recommended. Fluid and white matter suppression (FWMS) sequences have also been proposed to detect the transmantle sign in FCD type II.…”

Section: Polymicrogyria (Barkovich Group Iii)mentioning

confidence: 99%

7T Epilepsy Task Force Consensus Recommendations on the Use of 7T MRI in Clinical Practice

Opheim

Kolk²,

Bloch³

et al. 2021

Neurology

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Identifying a structural brain lesion on MRI has important implications in epilepsy and is the most important correlate to seizure freedom after surgery in patients with drug-resistant focal onset epilepsy. However, at conventional magnetic field strengths (1.5 and 3T) only around 60-85% of MRI examinations reveal such lesions. Over the last decade, studies have demonstrated the added value of 7T MRI in patients with and without known epileptogenic lesions from 1.5 and/or 3T. However, translation of 7T MRI to clinical practice is still challenging, particularly in centers new to 7T, and there is a need for practical recommendations on targeted use of 7T MRI in the clinical management of patients with epilepsy. The 7T Epilepsy Task Force - an international group representing 21 7T MRI centers with experience from scanning over 2000 patients with epilepsy – would hereby like to share its experience with the neurology community regarding the appropriate clinical indications, patient selection and preparation, acquisition protocols and setup, technical challenges, and radiological guidelines for 7T MRI in epilepsy patients. This article mainly addresses structural imaging, but also presents multiple non-structural MRI techniques that benefit from 7T and hold promise as future directions in epilepsy. Answering to the increased availability of 7T MRI as an approved tool for diagnostic purposes, this article aims to give guidance on clinical 7T MRI epilepsy management by giving recommendations on referral, suitable 7T MRI protocols and image interpretation.

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Section: Polymicrogyria (Barkovich Group Iii)mentioning

confidence: 99%

7T Epilepsy Task Force Consensus Recommendations on the Use of 7T MRI in Clinical Practice

Opheim

Kolk²,

Bloch³

et al. 2021

Neurology

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“…This necessitates the research and development of analytical methods capable of inferring microstructural information from mm-scale measurements to bypass resolution limits imposed by the MRI hardware. The need for reproducible and quantitative MRI has prompted the development of methods capable of linking mm-scale MRI measurements with biologically interpretable information [1][2][3][4][5][6][7]. Here, an appropriate mathematical model in conjunction with specifically collected MRI data results in model parameters sensitive at the microscale.…”

Section: Introductionmentioning

confidence: 99%

Fractional Order Magnetic Resonance Fingerprinting in the Human Cerebral Cortex

et al. 2021

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Mathematical models are becoming increasingly important in magnetic resonance imaging (MRI), as they provide a mechanistic approach for making a link between tissue microstructure and signals acquired using the medical imaging instrument. The Bloch equations, which describes spin and relaxation in a magnetic field, are a set of integer order differential equations with a solution exhibiting mono-exponential behaviour in time. Parameters of the model may be estimated using a non-linear solver or by creating a dictionary of model parameters from which MRI signals are simulated and then matched with experiment. We have previously shown the potential efficacy of a magnetic resonance fingerprinting (MRF) approach, i.e., dictionary matching based on the classical Bloch equations for parcellating the human cerebral cortex. However, this classical model is unable to describe in full the mm-scale MRI signal generated based on an heterogenous and complex tissue micro-environment. The time-fractional order Bloch equations have been shown to provide, as a function of time, a good fit of brain MRI signals. The time-fractional model has solutions in the form of Mittag–Leffler functions that generalise conventional exponential relaxation. Such functions have been shown by others to be useful for describing dielectric and viscoelastic relaxation in complex heterogeneous materials. Hence, we replaced the integer order Bloch equations with the previously reported time-fractional counterpart within the MRF framework and performed experiments to parcellate human gray matter, which consists of cortical brain tissue with different cyto-architecture at different spatial locations. Our findings suggest that the time-fractional order parameters, α and β, potentially associate with the effect of interareal architectonic variability, which hypothetically results in more accurate cortical parcellation.

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“…We extended the model to 11 parameters in prior work, where the additional parameter was used to account for the noise floor in the GRE-MRI data and applied it to regions of the corpus callosum (Thapaliya et al, 2018). Model variants have been used to study lesions in relapsing-remitting multiple sclerosis patients (Li et al, 2015) and dysplastic tissue regions in focal epilepsy (Thapaliya et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Influence of 7T GRE-MRI Signal Compartment Model Choice on Tissue Parameters

et al. 2020

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Quantitative assessment of tissue microstructure is important in studying human brain diseases and disorders. Ultra-high field magnetic resonance imaging (MRI) data obtained using a multi-echo gradient echo sequence have been shown to contain information on myelin, axonal, and extracellular compartments in tissue. Quantitative assessment of water fraction, relaxation time (T 2 *), and frequency shift using multicompartment models has been shown to be useful in studying white matter properties via specific tissue parameters. It remains unclear how tissue parameters vary with model selection based on 7T multiple echo time gradient-recalled echo (GRE) MRI data. We applied existing signal compartment models to the corpus callosum and investigated whether a three-compartment model can be reduced to two compartments and still resolve white matter parameters [i.e., myelin water fraction (MWF) and g-ratio]. We show that MWF should be computed using a three-compartment model in the corpus callosum, and the g-ratios obtained using three compartment models are consistent with previous reports. We provide results for other parameters, such as signal compartment frequency shifts.

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7T GRE-MRI signal compartments are sensitive to dysplastic tissue in focal epilepsy

Cited by 12 publications

References 56 publications

7T Epilepsy Task Force Consensus Recommendations on the Use of 7T MRI in Clinical Practice

7T Epilepsy Task Force Consensus Recommendations on the Use of 7T MRI in Clinical Practice

Fractional Order Magnetic Resonance Fingerprinting in the Human Cerebral Cortex

Influence of 7T GRE-MRI Signal Compartment Model Choice on Tissue Parameters

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