MRI Unit

Chalfont Saint Giles, United Kingdom
Chalfont Saint Giles, United Kingdom

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Park M.T.M.,Kimel Family Translational Imaging Genetics Research Laboratory | Pipitone J.,Kimel Family Translational Imaging Genetics Research Laboratory | Baer L.H.,Concordia University at Montréal | Winterburn J.L.,Kimel Family Translational Imaging Genetics Research Laboratory | And 13 more authors.
NeuroImage | Year: 2014

The cerebellum has classically been linked to motor learning and coordination. However, there is renewed interest in the role of the cerebellum in non-motor functions such as cognition and in the context of different neuropsychiatric disorders. The contribution of neuroimaging studies to advancing understanding of cerebellar structure and function has been limited, partly due to the cerebellum being understudied as a result of contrast and resolution limitations of standard structural magnetic resonance images (MRI). These limitations inhibit proper visualization of the highly compact and detailed cerebellar foliations. In addition, there is a lack of robust algorithms that automatically and reliably identify the cerebellum and its subregions, further complicating the design of large-scale studies of the cerebellum. As such, automated segmentation of the cerebellar lobules would allow detailed population studies of the cerebellum and its subregions. In this manuscript, we describe a novel set of high-resolution in vivo atlases of the cerebellum developed by pairing MR imaging with a carefully validated manual segmentation protocol. Using these cerebellar atlases as inputs, we validate a novel automated segmentation algorithm that takes advantage of the neuroanatomical variability that exists in a given population under study in order to automatically identify the cerebellum, and its lobules. Our automatic segmentation results demonstrate good accuracy in the identification of all lobules (mean Kappa [κ]=. 0.731; range 0.40-0.89), and the entire cerebellum (mean κ=. 0.925; range 0.90-0.94) when compared to "gold-standard" manual segmentations. These results compare favorably in comparison to other publically available methods for automatic segmentation of the cerebellum. The completed cerebellar atlases are available freely online ( and can be customized to the unique neuroanatomy of different subjects using the proposed segmentation pipeline ( © 2014 Elsevier Inc.

Murta T.,University College London | Murta T.,University of Lisbon | Leite M.,University College London | Leite M.,University of Lisbon | And 4 more authors.
Human Brain Mapping | Year: 2015

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are important tools in cognitive and clinical neuroscience. Combined EEG-fMRI has been shown to help to characterise brain networks involved in epileptic activity, as well as in different sensory, motor and cognitive functions. A good understanding of the electrophysiological correlates of the blood oxygen level-dependent (BOLD) signal is necessary to interpret fMRI maps, particularly when obtained in combination with EEG. We review the current understanding of electrophysiological-haemodynamic correlates, during different types of brain activity. We start by describing the basic mechanisms underlying EEG and BOLD signals and proceed by reviewing EEG-informed fMRI studies using fMRI to map specific EEG phenomena over the entire brain (EEG-fMRI mapping), or exploring a range of EEG-derived quantities to determine which best explain colocalised BOLD fluctuations (local EEG-fMRI coupling). While reviewing studies of different forms of brain activity (epileptic and nonepileptic spontaneous activity; cognitive, sensory and motor functions), a significant attention is given to epilepsy because the investigation of its haemodynamic correlates is the most common application of EEG-informed fMRI. Our review is focused on EEG-informed fMRI, an asymmetric approach of data integration. We give special attention to the invasiveness of electrophysiological measurements and the simultaneity of multimodal acquisitions because these methodological aspects determine the nature of the conclusions that can be drawn from EEG-informed fMRI studies. We emphasise the advantages of, and need for, simultaneous intracranial EEG-fMRI studies in humans, which recently became available and hold great potential to improve our understanding of the electrophysiological correlates of BOLD fluctuations. Hum Brain Mapp, 36:391-414, 2015. © 2014 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Vulliemoz S.,University College London | Vulliemoz S.,MRI Unit | Vulliemoz S.,University of Geneva | Lemieux L.,University College London | And 6 more authors.
Epilepsia | Year: 2010

Functional electrophysiologic techniques such as electroencephalography (EEG) and magnetoencephalography (MEG) give insights into the dynamics of the networks involved in the generation of interictal and ictal epileptic activity and their interaction with physiologic brain activity. With recent advances in methodology and clinical validation, EEG source imaging (ESI) may now be used to map epileptic activity as well as evoked responses to external stimuli. By its ability to show hemodynamic changes time locked to epileptic activity in the whole brain, EEG-correlated functional magnetic resonance imaging (fMRI) (EEG-fMRI) is the natural counterpart of ESI, circumventing some of its limitations, the former adding data from the depths of the brain, and the latter temporal resolution. To better understand the potential and limitations of both techniques, this review starts with a description of the neurophysiologic mechanisms that give rise to the measured signals, followed by validation studies based on comparison with intracranial EEG and surgical outcome. We then discuss analysis strategies to combine both techniques by reviewing studies in epilepsy, current methodologic development, and future directions of this fast-developing field. © 2009 International League Against Epilepsy.

Sempere A.P.,Hospital General Universitario Of Alicante | Martin-Medina P.,MRI Unit | Berenguer-Ruiz L.,Hospital Marina Baixa | Perez-Carmona N.,Hospital Marina Baixa | And 3 more authors.
Acta Neurologica Scandinavica | Year: 2013

Background: Multiple sclerosis patients who discontinue using natalizumab are at risk of a rebound in disease activity. However, the optimal alternative therapy is not currently known. Aims of the study: We report on clinical and MRI data and patient safety in a group of relapsing-remitting multiple sclerosis patients who tested seropositive for the JC virus and who have switched from natalizumab to fingolimod because of concerns regarding PML risks. Methods: The test for JC virus antibodies was performed in 18 relapsing-remitting multiple sclerosis patients who were being treated with natalizumab for more than 1 year. Eight seropositive patients switched to fingolimod while the seronegative patients continued with natalizumab. Results: After switching to fingolimod, five of eight patients (63%) experienced clinical relapses, and MRI activity was detected in six of eight patients (75%). Neither clinical relapses nor MRI activity was observed in the patients who continued with natalizumab. No serious adverse effects were detected. Conclusions: Natalizumab is an effective treatment for relapsing-remitting multiple sclerosis, but its discontinuation continues to be a complex problem. All of the therapies tried thus far, including fingolimod, have been unable to control the reactivation of the disease. Further studies addressing alternative therapies after natalizumab discontinuation are necessary. © 2013 John Wiley & Sons A/S.

Roldan-Valadez E.,MRI Unit | Rios C.,National Institute of Neurology and Neurosurgery | Suarez-May M.A.,MRI Unit | Favila R.,General Electric | Aguilar-Castaneda E.,National Institute of Neurology and Neurosurgery
Anatomical Record | Year: 2013

Introduction: Macroanatomical right-left hemispheric differences in the brain are termed asymmetries, although there is no clear information on the global influence of gender and brain-regions. The aim of this study was to evaluate the main effects and interactions of these variables on the measurement of volumetric asymmetry indices (VAIs). Materials and methods: Forty-seven healthy young-adult volunteers (23 males, 24 females) agreed to undergo brain magnetic resonance imaging in a 3T scanner. Image post processing using voxel-based volumetry allowed the calculation of 54 VAIs from the frontal, temporal, parietal and occipital lobes, limbic system, basal ganglia, and cerebellum for each cerebral hemisphere. Multivariate ANCOVA analysis calculated the main effects and interactions on VAIs of gender and brain regions controlling the effect of age. Results: The only significant finding was the main effect of brain regions (F (6, 9373.605) 44.369, P<.001; partial η2=.101, and power of 1.0), with no significant interaction between gender and brain regions (F (6, 50.517) .239, P=.964). Conclusion: Volumetric asymmetries are present across all brain regions, with larger values found in the limbic system and parietal lobe. The absence of a significant influence of gender and age in the evaluation of the numerous measurements generated by multivariate analyses in this study should not discourage researchers to report and interpret similar results, as this topic still deserves further assessment. © 2013 Wiley Periodicals, Inc.

Nowell M.,University College London | Nowell M.,National Hospital for Neurology and Neurosurgery | Nowell M.,MRI Unit | Rodionov R.,University College London | And 13 more authors.
Epilepsia | Year: 2015

Objective We present a single-center prospective study, validating the use of 3D multimodality imaging (3DMMI) in patients undergoing intracranial electroencephalography (IC-EEG). Methods IC-EEG implantation preparation entails first designing of the overall strategy of implantation (strategy) and second the precise details of implantation (planning). For each case, the multidisciplinary team made decisions on strategy and planning before the disclosure of multimodal brain imaging models. Any changes to decisions, following disclosure of the multimodal models, were recorded. Results Disclosure of 3DMMI led to a change in strategy in 15 (34%) of 44 individuals. The changes included addition and subtraction of electrodes, addition of grids, and going directly to resection. For the detailed surgical planning, 3DMMI led to a change in 35 (81%) of 43 individuals. Twenty-five (100%) of 25 patients undergoing stereo-EEG (SEEG) underwent a change in electrode placement, with 158 (75%) of 212 electrode trajectories being altered. Significance The use of 3DMMI makes substantial changes in clinical decision making. © Wiley Periodicals, Inc. © 2015 International League Against Epilepsy.

Chaudhary U.J.,University College London | Chaudhary U.J.,MRI Unit | Duncan J.S.,University College London | Duncan J.S.,MRI Unit | Duncan J.S.,UCLH NHS Foundation Trust
Neuroimaging Clinics of North America | Year: 2014

The lifetime prevalence of epilepsy ranges from 2.7 to 12.4 per 1000 in Western countries. Around 30% of patients with epilepsy remain refractory to antiepileptic drugs and continue to have seizures. Noninvasive imaging techniques such as functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) have helped to better understand mechanisms of seizure generation and propagation, and to localize epileptic, eloquent, and cognitive networks. In this review, the clinical applications of fMRI and DTI are discussed, for mapping cognitive and epileptic networks and organization of white matter tracts in individuals with epilepsy. © 2014 Elsevier Inc.

Sempere A.P.,Hospital General Universitario Of Alicante | Mola S.,Hospital Vega Baja | Martin-Medina P.,MRI Unit | Bernabeu A.,MRI Unit | And 2 more authors.
Journal of Neuroimaging | Year: 2013

Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is a recently defined inflammatory central nervous system disorder responsive to steroids with characteristic magnetic resonance imaging (MRI) features. We report a 69-year-old man presenting with gait ataxia with the characteristic MRI features of CLIPPERS and describe the clinical, MRI, and magnetic resonance spectroscopy (MRS) follow-up after treatment with glucocorticosteroids. Brain and spine MRI showed punctate enhancement peppering the brainstem, cerebellar peduncles, and upper cervical cord. In MRS, the ratio of N-acetyl aspartate to creatine (NAA/Cr) was significantly decreased in the pons and both thalami. An extensive evaluation found no alternative diagnoses. Treatment with steroids led to rapid clinical improvement. Repeat MRI and MRS showed complete resolution of gadolinium-enhancing lesions and recovery of NAA/Cr levels in the pons and thalami. After 1 month of tapering oral steroids, weekly oral methotrexate was started and the patient has remained stable for the past 6 months. © 2011 by the American Society of Neuroimaging.

Chaudhary U.J.,University College London | Chaudhary U.J.,MRI Unit | Duncan J.S.,University College London | Duncan J.S.,National Hospital for Neurology and Neurosurgery | Lemieux L.,University College London
Human Brain Mapping | Year: 2013

Functional magnetic resonance imaging (fMRI) is able to detect changes in blood oxygenation level associated with neuronal activity throughout the brain. For more than a decade, fMRI alone or in combination with simultaneous EEG recording (EEG-fMRI) has been used to investigate the hemodynamic changes associated with interictal and ictal epileptic discharges. This is the first literature review to focus on the various fMRI acquisition and data analysis methods applied to map epileptic seizure-related hemodynamic changes from the first report of an fMRI scan of a seizure to the present day. Two types of data analysis approaches, based on temporal correlation and data driven, are explained and contrasted. The spatial and temporal relationship between the observed hemodynamic changes using fMRI and other non-invasive and invasive electrophysiological and imaging data is considered. We then describe the role of fMRI in localizing and exploring the networks involved in spontaneous and triggered seizure onset and propagation. We also discuss that fMRI alone and combined with EEG hold great promise in the investigation of seizure-related hemodynamic changes non-invasively in humans. We think that this will lead to significant improvements in our understanding of seizures with important consequences for the treatment of epilepsy. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.

Chaudhary U.J.,University College London | Duncan J.S.,University College London | Lemieux L.,University College London | Lemieux L.,MRI Unit
Epilepsy and Behavior | Year: 2011

Epilepsy is one of the few neurological disorders to be recognized in Antiquity. The etiology of epilepsy has evolved from affliction of evil spirits and bad omens to an organic disease of the brain. Geographically separate cultures have recognized the diverse symptomatology of epilepsy from vigorous convulsions to spontaneous localized jerking since times immemorial. Similarly, the diagnostic procedures and treatment options have varied in different milieus. In this review we have followed the course of history chronologically from Babylonians to Hughlings Jackson, mapping the conceptual development of epilepsy and the origin of some of the positive and negative attitudes inherited into today's epileptology. Original writings, such as Hughlings Jackson's letters, and English translations of early Latin work, where available, were used as primary sources of information. Where primary sources were not accessible, we consulted research articles, books, and commentaries by eminent historians and epileptologists. © 2011 Elsevier Inc.

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