Search results for: Marios C. Yiannakas

Items from 1 to 12 out of 12 results

article

Multi‐echo quantitative susceptibility mapping: how to combine echoes for accuracy and precision at 3 Tesla

Emma Biondetti, Anita Karsa, Francesco Grussu, Marco Battiston, more

Magnetic Resonance in Medicine > 88 > 5 > 2101 - 2116

Purpose To compare different multi‐echo combination methods for MRI QSM. Given the current lack of consensus, we aimed to elucidate how to optimally combine multi‐echo gradient‐recalled echo signal phase information, either before or after applying Laplacian‐base methods (LBMs) for phase unwrapping or background field removal. Methods Multi‐echo gradient‐recalled echo data were simulated in a numerical...

article

Comparison of multicenter MRI protocols for visualizing the spinal cord gray matter

Julien Cohen‐Adad, Eva Alonso‐Ortiz, Stephanie Alley, Maria Marcella Lagana, more

Magnetic Resonance in Medicine > 88 > 2 > 849 - 859

Purpose Spinal cord gray‐matter imaging is valuable for a number of applications, but remains challenging. The purpose of this work was to compare various MRI protocols at 1.5 T, 3 T, and 7 T for visualizing the gray matter. Methods In vivo data of the cervical spinal cord were collected from nine different imaging centers. Data processing consisted of automatically segmenting the spinal cord and...

article

Sodium in the Relapsing–Remitting Multiple Sclerosis Spinal Cord: Increased Concentrations and Associations With Microstructural Tissue Anisotropy

Bhavana S. Solanky, Ferran Prados, Carmen Tur, Marios C. Yiannakas, more

Journal of Magnetic Resonance Imaging > 52 > 5 > 1429 - 1438

Background Associations between brain total sodium concentration, disability, and disease progression have recently been reported in multiple sclerosis. However, such measures in spinal cord have not been reported. Purpose To measure total sodium concentration (TSC) alterations in the cervical spinal cord of people with relapsing–remitting multiple sclerosis (RRMS) and a control cohort using sodium...

article

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

Marco Battiston, Torben Schneider, Francesco Grussu, Marios C. Yiannakas, more

Magnetic Resonance in Medicine > 82 > 3 > 1025 - 1040

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_{2}^{B}

). A sequence...

article

Gray vs. White Matter Segmentation of the Conus Medullaris: Reliability and Variability in Healthy Volunteers

Marios C. Yiannakas, Martina D. Liechti, Nuttakarn Budtarad, Patrick Cullinane, more

Journal of Neuroimaging > 29 > 3 > 410 - 417

BACKGROUND AND PURPOSE Magnetic resonance imaging (MRI)‐derived spinal cord (SC) gray and white matter (GM/WM) volume are useful indirect measures of atrophy and neurodegeneration over time, typically obtained in the upper SC. Neuropathological evidence suggests that in certain neurological conditions, early degeneration may occur as low as the sacral SC. In this study, the feasibility of GM/WM segmentation...

article

Fast and reproducible in vivo T₁ mapping of the human cervical spinal cord

Marco Battiston, Torben Schneider, Ferran Prados, Francesco Grussu, more

Magnetic Resonance in Medicine > 79 > 4 > 2142 - 2148

Purpose To develop a fast and robust method for measuring T₁ in the whole cervical spinal cord in vivo, and to assess its reproducibility. Methods A spatially nonselective adiabatic inversion pulse is combined with zonally oblique‐magnified multislice echo‐planar imaging to produce a reduced field‐of‐view inversion‐recovery echo‐planar imaging protocol. Multi‐ inversion time data are obtained by...

article

Spinal cord grey matter segmentation challenge

Ferran Prados, John Ashburner, Claudia Blaiotta, Tom Brosch, more

NeuroImage > 2017 > 152 > C > 312-329

An important image processing step in spinal cord magnetic resonance imaging is the ability to reliably and accurately segment grey and white matter for tissue specific analysis. There are several semi- or fully-automated segmentation methods for cervical cord cross-sectional area measurement with an excellent performance close or equal to the manual segmentation. However, grey matter segmentation...

article

Phenytoin for neuroprotection in patients with acute optic neuritis: a randomised, placebo-controlled, phase 2 trial

Rhian Raftopoulos, Simon J Hickman, Ahmed Toosy, Basil Sharrack, more

The Lancet Neurology > 2016 > 15 > 3 > 259-269

Acute demyelinating optic neuritis, a common feature of multiple sclerosis, can damage vision through neurodegeneration in the optic nerve and in its fibres in the retina. Inhibition of voltage-gated sodium channels is neuroprotective in preclinical models. In this study we aimed to establish whether sodium-channel inhibition with phenytoin is neuroprotective in patient with acute optic neuritis.We...

article

Fully automated segmentation of the cervical cord from T1-weighted MRI using PropSeg: Application to multiple sclerosis

Marios C. Yiannakas, Ahmed M. Mustafa, Benjamin De Leener, Hugh Kearney, more

NeuroImage: Clinical > 2016 > 10 > C > 71-77

Spinal cord (SC) atrophy, i.e. a reduction in the SC cross-sectional area (CSA) over time, can be measured by means of image segmentation using magnetic resonance imaging (MRI). However, segmentation methods have been limited by factors relating to reproducibility or sensitivity to change. The purpose of this study was to evaluate a fully automated SC segmentation method (PropSeg), and compare this...

article

Improved MRI quantification of spinal cord atrophy in multiple sclerosis

Hugh Kearney, Marios C. Yiannakas, Khaled Abdel‐Aziz, Claudia A.M. Wheeler‐Kingshott, more

Journal of Magnetic Resonance Imaging > 39 > 3 > 617 - 623

PurposeTo identify an improved method for measuring spinal cord cross‐sectional area (CSA) using magnetic resonance imaging (MRI) in multiple sclerosis (MS). Materials and MethodsMRI was performed on 15 controls and 15 MS patients and repeated in nine controls and nine patients after 6 months. At this timepoint, an additional scan was acquired to evaluate scan–rescan reproducibility. Two sequences...

article

In vivo magnetic resonance spectroscopy detection of combined glutamate‐glutamine in healthy upper cervical cord at 3 T

Bhavana S Solanky, Khaled Abdel‐Aziz, Marios C Yiannakas, Alaine M Berry, more

NMR in Biomedicine > 26 > 3 > 357 - 366

The possibility of quantifying the superimposed signal of glutamate and glutamine (Glx) and its components by ¹ H magnetic resonance spectroscopy (MRS) in the spinal cord is an exciting challenge with important clinical applications in neurological conditions. The spinal cord is a particularly difficult region of interest due to its small volume, magnetic field inhomogeneities and physiological motion...

article

A method for measuring the cross sectional area of the anterior portion of the optic nerve in vivo using a fast 3D MRI sequence

Marios C. Yiannakas, Claudia A.M. Wheeler‐Kingshott, Alaine M. Berry, Karyn Chappell, more

Journal of Magnetic Resonance Imaging > 31 > 6 > 1486 - 1491

Purpose:To investigate the three‐dimensional (3D) fast‐recovery fast spin‐echo accelerated (FRFSE‐XL) sequence as a new application for measuring the intraorbital optic nerve (ION) mean cross‐sectional area in vivo and to determine its value within a commonly used high resolution imaging protocol. Materials and Methods:The entire ION was scanned in nine healthy volunteers (mean age 32 ± 4 years)...

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