Добірка наукової літератури з теми "Magnetic resonance imaging, voxel based morphometry, tract based spatial statistics"

Background: Several authors have used advanced magnetic resonance imaging (MRI) techniques to investigate whether patients with neuromyelitis optica (NMO) have occult damage in normal-appearing brain tissue, similarly to multiple sclerosis (MS). To date, the literature contains no data derived from the combined use of several advanced MRI techniques in the same NMO subjects. Objective: We set out to determine whether occult damage could be detected in the normal-appearing brain tissue of a small group of patients with NMO using a multiparametric MRI approach. Methods: Eight female patients affected by NMO (age range 44–58 years) and seven sex- and age-matched healthy controls were included. The techniques used on a 1.5 T MRI imaging scanner were magnetization transfer imaging, diffusion tensor imaging, tract-based spatial statistics, spectroscopy and voxel-based morphometry in order to analyse normal-appearing white matter and normal-appearing grey matter. Results: Structural and metabolic parameters showed no abnormalities in normal-appearing white matter of patients with NMO. Conversely, tract-based spatial statistics demonstrated a selective alteration of the optic pathways and the lateral geniculate nuclei. Diffusion tensor imaging values in the normal-appearing grey matter were found to be significantly different in the patients with NMO versus the healthy controls. Moreover, voxel-based morphometry analysis demonstrated a significant density and volume reduction of the sensorimotor cortex and the visual cortex. Conclusions: Our data disclosed occult structural damage in the brain of patients with NMO, predominantly involving regions connected with motor and visual systems. This damage seems to be the direct consequence of transsynaptic degeneration triggered by lesions of the optic nerve and spine.

Clinical differentiation of parkinsonian syndromes such as the Parkinson variant of multiple system atrophy (MSA-P) and cerebellar subtype (MSA-C) from Parkinson's disease is difficult in the early stage of the disease. To identify the correlative pattern of brain changes for differentiating parkinsonian syndromes, we applied discriminant analysis techniques by magnetic resonance imaging (MRI). T1-weighted volume data and diffusion tensor images were obtained by MRI in eighteen patients with MSA-C, 12 patients with MSA-P, 21 patients with Parkinson’s disease, and 21 healthy controls. They were evaluated using voxel-based morphometry and tract-based spatial statistics, respectively. Discriminant functions derived by step wise methods resulted in correct classification rates of 0.89. When differentiating these diseases with the use of three independent variables together, the correct classification rate was the same as that obtained with step wise methods. These findings support the view that each parkinsonian syndrome has structural deviations in multiple brain areas and that a combination of structural brain measures can help to distinguish parkinsonian syndromes.

BackgroundPrevious morphology and diffusion-imaging studies have suggested that structural changes in white matter is an important part of the pathophysiology of obsessive–compulsive disorder (OCD). However, different methodological approaches and the heterogeneity of patient samples question the validity of the findings.Materials and methodsIn total, 30 patients were matched for age and sex with 30 healthy controls. All participants underwent T1-weighted magnetic resonance imaging, diffusion tensor imaging and T2 fluid-attenuated inversion recovery. Voxel-based morphometry and tract-based spatial statistics were used to compare white matter volumes and diffusion tensor imaging between groups. These data were analysed correcting for the effects of multiple comparisons, age, sex, severity and duration of illness as nuisance covariates. White matter hyperintensities were manually identified.ResultsIncrease in fractional anisotropy in cerebellum was the most prominent result. A decrease in fractional anisotrophy in patients comparable with previous studies was located in forceps minor. There were no differences in the white matter morphology or in the white matter hyperintensities between patients and healthy controls.ConclusionDecrease in fractional anisotrophy in forceps minor and increase in cerebellum were found, and they were not due to neither white matter hyperintensities nor morphology of the white matter. Cerebellar hyperconnectivity could be an important part of OCD pathophysiology.

Background Medication-overuse headache is a common clinical entity, but neuroimaging studies investigating volumetric and microstructural alterations of the brain in medication-overuse headache are rare. Therefore, in the current longitidunal study we evaluated gray matter volume and white matter integrity in patients with medication-overuse headache before and after drug withdrawal. Methods A prospective study evaluated 27 patients with medication-overuse headache and 27 age-, sex-, and education-matched healthy adults. High-resolution T1-weighted magnetic resonance imaging and diffusion tensor imaging were obtained from the control group and medication-overuse headache patients before and six months after drug withdrawal. Tract-based spatial statistics of multiple diffusivity indices and voxel-based morphometry were employed to investigate white and gray matter abnormalities. Results No correlation was found between age, gender, education and smoking status in both groups. The most commonly overused medications were simple analgesics (96.3%) and combined analgesics (3.7%). The mean duration of the history of medication overuse and headaches was 56.7 ± 63.5 months. White matter diffusional and gray matter morphological alterations including volume, fractional anisotropy, radial diffusivity, and axial diffusivity analyses showed no significant relationship in the patients before and six months after withdrawal of analgesics. Also no difference was observed between the patients versus controls. Conclusion Our data demonstrated no structural alterations within the brain in medication-overuse headache.

Abstract This study aimed to investigate the brain grey matter volume (GMV) related to problematic mobile phone use (PMPU), and whether these regions of GMV play a potential moderating role in the relationship between PMPU and depressive symptoms. We recruited 266 students who underwent magnetic resonance imaging (MRI) scanning. PMPU and depressive symptoms were assessed by a self-rating questionnaire for adolescent PMPU and patient health questionnaire-9, respectively. A multiple regression model was performed to detect GMV and white matter (WM) integrity associated with PMPU by voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) methods, and the moderating analysis was conducted by PROCESS using SPSS software. VBM analysis found an inverse correlation between the GMV of the anterior cingulate gyrus (ACC) and right fusiform gyrus (FFG) with PMPU (PFDR < 0.05), and TBSS analysis revealed that fractional anisotropy (FA) in the body of the corpus callosum was negatively correlated with PMPU. The correlation between PMPU and depressive symptoms was moderated by the GMV of the ACC. These results suggest that the GMV of the ACC and right FFG, as well as FA in the body of the corpus callosum, was related to PMPU, and we further found that increased GMV of the ACC could reduce the relationship between PMPU and depressive symptoms in college students.

BackgroundLate-life depression is a common and heterogeneous illness, associated with structural abnormalities in both grey and white matter.AimsTo examine the relationship between age at onset and magnetic resonance imaging (MRI) measures of grey and white matter to establish whether they support particular hypotheses regarding the anatomy and aetiology of network disruption in late-life depression.MethodWe studied 36 participants with late-life depression. Grey matter was examined using T1-weighted MRI and analysed using voxel-based morphometry. The hippocampus was automatically segmented and volume and shape analysis performed. White matter was examined using diffusion tensor imaging and analysed using tract-based spatial statistics.ResultsLater age at onset was significantly associated with reduced fractional anisotropy of widespread tracts, in particular the anterior thalamic radiation and superior longitudinal fasciculus. Earlier age at onset was associated with reduced hippocampal volume normalised to whole brain size bilaterally. However, no significant correlations were detected using hippocampal shape analysis or voxel-based morphometry.ConclusionsOverall, the results were compatible with the vascular hypothesis, and provided some support for the glucocorticoid cascade hypothesis.

Background Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that reflects the Brownian motion of water molecules constrained within brain tissue. Fractional anisotropy (FA) is one of the most commonly measured DTI parameters, and can be applied to quantitative analysis of white matter as tract-based spatial statistics (TBSS) and voxel-wise analysis. Purpose To show an association between metallic implants and the results of statistical analysis (voxel-wise group comparison and TBSS) for fractional anisotropy (FA) mapping, in DTI of healthy adults. Material and Methods Sixteen healthy volunteers were scanned with 3-Tesla MRI. A magnetic keeper type of dental implant was used as the metallic implant. DTI was acquired three times in each participant: (i) without a magnetic keeper (FAnon1); (ii) with a magnetic keeper (FAimp); and (iii) without a magnetic keeper (FAnon2) as reproducibility of FAnon1. Group comparisons with paired t-test were performed as FAnon1 vs. FAnon2, and as FAnon1 vs. FAimp. Results Regions of significantly reduced and increased local FA values were revealed by voxel-wise group comparison analysis (a P value of less than 0.05, corrected with family-wise error), but not by TBSS. Conclusion Metallic implants existing outside the field of view produce artifacts that affect the statistical analysis (voxel-wise group comparisons) for FA mapping. When statistical analysis for FA mapping is conducted by researchers, it is important to pay attention to any dental implants present in the mouths of the participants.

Objective: Using diffusion tensor magnetic resonance imaging (DT MRI), we analyzed the architectural integrity of the brain white matter (WM) from a large cohort of MS patients to identify the structural substrates of the concomitant presence of depression and fatigue. Methods: Brain dual-echo, 3D T1-weighted and DT MRI scans were acquired from 147 MS patients and 90 gender- and age-matched healthy controls (HCs). Patients were stratified by the presence of depression (92 depressed (D), 55 not depressed (nD)) and fatigue (81 fatigued (F), 66 not fatigued (nF)). Sixty-five patients had co-occurrence of depression and fatigue (DF). Whole-brain voxel-wise comparisons of WM DT MRI abnormalities were performed using tract-based-spatial-statistics (TBSS). Tract-specific analyses were run in brain WM tracts using standard-space templates. Results: Whole-brain voxel-wise analysis yielded no significant differences between patient subgroups. At tract-specific analysis, DF patients had reduced fractional anisotropy (FA) of the forceps minor. Reduced FA of the right anterior thalamic radiation and right uncinate fasciculus was found in F-MS vs not F-MS patients after correcting for depression. No significant differences were found between D vs not D-MS patients, after correcting for fatigue. Conclusions: This study provides evidence for partially overlapping damage to frontal and fronto-temporal pathways underlying depression and fatigue in MS.

Objective This study was performed to investigate structural abnormalities of the white matter in patients with comitant exotropia using the tract-based spatial statistics (TBSS) method. Methods Diffusion tensor imaging data from magnetic resonance images of the brain were collected from 20 patients with comitant exotropia and 20 age- and sex-matched healthy controls. The FMRIB Software Library was used to compute the diffusion measures, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). These measures were obtained using voxel-wise statistics with threshold-free cluster enhancement. Results The FA values in the right inferior fronto-occipital fasciculus (IFO) and right inferior longitudinal fasciculus were significantly higher and the RD values in the bilateral IFO, forceps minor, left anterior corona radiata, and left anterior thalamic radiation were significantly lower in the comitant exotropia group than in the healthy controls. No significant differences in the MD or AD values were found between the two groups. Conclusions Alterations in FA and RD values may indicate the underlying neuropathologic mechanism of comitant exotropia. The TBSS method can be a useful tool to investigate neuronal tract participation in patients with this disease.

Abstract Background Treatment-resistant depression is among the most debilitating conditions in psychiatry. Recent studies have associated alterations in white matter microstructure measured with magnetic resonance imaging with poor antidepressant response. Therefore, the extent to which electroconvulsive therapy, the most effective therapeutic option for treatment-resistant depression, affects white matter microstructure warrants investigation. Methods A total 13 patients suffering from severe unipolar treatment-resistant depression underwent magnetic resonance imaging with a diffusion tensor imaging sequence before and after undergoing a series of right unilateral electroconvulsive therapy. Diffusivity metrics were compared voxel-wise using tract-based spatial statistics and repeated-measures ANOVA. Results A total 12 patients responded to electroconvulsive therapy and 9 were classified as remitters. An increase in axial diffusivity was observed in the posterior limb of the internal capsule of the right hemisphere (PFWE ≤ .05). The increase in this area was higher in the right compared with the left hemisphere (P < .05). No correlation of this effect with treatment response could be found. Conclusions The strong lateralization of effects to the hemisphere of electrical stimulation suggests an effect of electroconvulsive therapy on diffusivity metrics which is dependent of electrode placement. Investigation in controlled studies is necessary to reveal to what extent the effects of electroconvulsive therapy on white matter microstructure are related to clinical outcomes and electrode placement.

Cognitive impairment strongly affects people with multiple sclerosis (MS). It comprises multifactorial symptoms and no consistent treatments are available to date. Although cognitive impairment has been observed in all stages of the disease, the majority of studies mainly focused on a specific clinical phenotype (primarily relapsing-remitting MS) or did not differentiate between MS subtypes. Advanced magnetic resonance imaging (MRI) techniques are providing useful measures of functional and structural abnormalities in patients with MS, allowing to overcome the limits of conventional MRI. This thesis wished to improve the understanding of the mechanisms responsible for the accumulation of cognitive dysfunction in patients with relapse-onset MS by combining different advanced structural and functional MRI techniques. First, we applied functional MRI (fMRI) to assess brain functional reorganization in relation to different cognitive tasks (face encoding and N-back) in patients with the main relapse-onset clinical phenotypes. We also explored the relationship between functional network alterations and clinical, cognitive, behavioural and structural MRI measures of disease-related damage. Our results provide new evidence for the debate about adaptive/maladaptive functional reorganization in MS, specifically in relation to the clinical and cognitive characteristics of MS phenotypes. Second, the investigation of resting state default mode network (DMN) functional connectivity enabled us to highlight that different modulations of DMN recruitment lead to different clinical profiles and manifestations. Moreover, functional connectivity of specific DMN areas (hippocampi) was found to be central for the assessment of important cognition-related aspects, such as depression. Finally, by applying voxel-wise MRI methods (VBM and TBSS) we explored the extent and distribution of brain GM atrophy and WM microstructural alterations in adult MS patients according to their age of disease onset, and we made some assumptions about the possible presence of pathophysiological mechanisms related to age of MS onset, that suggests a preserved reserve for structural plasticity that could modulate the structural and functional brain organization, in order to preserve or slow-down MS-related dysfunction. To conclude, the application of advanced MRI techniques allowed us to improve our knowledge on neuropsychological features in patients with relapse-onset MS.

A polineuropatia inflamatória desmielinizante crônica (PIDC) é uma síndrome caracterizada fundamentalmente pela disfunção do Sistema Nervoso Periférico e que afeta muito a qualidade de vida dos pacientes. O envolvimento da PIDC com o Sistema Nervoso Central tem sido descrito, maiormente como sendo subclínico, porém não há estudos sobre a caracterização deste envolvimento de uma forma ampla e quantitativa. Avaliamos 11 pacientes com PIDC, todos tratados e sem sinais clínicos de alterações centrais, e 11 controles, pareados em gênero e faixa etária de 19 a 69 anos. Foram adquiridas neuroimagens em uma máquina de Ressonância Magnética de alto campo (3T) usando diferentes técnicas de imagens; volumétricas ponderadas em T1, volumétricas de inversão e recuperação com atenuação de fluidos e ponderadas em T2, relaxométricas de cinco ecos para mapas de T2, de transferência de magnetização e por tensor de difusão. As imagens foram processadas em diferentes ferramentas computacionais e foram obtidos resultados para estudos da difusibilidade, volumetria, morfometria, tratometria e conectividade cerebral, além de achados radiológicos para os pacientes. As análises de grupos foram executadas por; 1) testes paramétricos monocaudais de duas amostras pareadas para os resultados da volumetria, da tratometria e conectividade cerebral; 2) mapeamento estatístico paramétrico para os resultados da morfometria baseada em voxel e; 3) estatística espacial baseada em tratos para os resultados da difusibilidade. Foram detectas alterações em todas as comparações. Os principais achados indicam um envolvimento possivelmente caracterizado por uma perda volumétrica encefálica generalizada, sobretudo nas regiões periventriculares associadas a ventrículos proeminentes acrescido de, um aumento da difusibilidade transversa e oblíqua nos maiores tratos de substância branca e, também há uma perda de densidade na substância branca periventricular e um aumento na substância cinzenta em uma região que sinaliza para o espessamento trigeminal bilateral e, uma redução geral da conectividade cerebral estrutural.
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a severe disease fundamentally characterized by dysfunction of the Peripheral Nervous System and affects greatly the quality of life of patients. The Central Nervous System (CNS) involvement in CIDP has not been described using recent quantitative neuroimaging techniques. We evaluated 11 patients with CIDP, all treated and without clinical signs of central alterations and 11 controls matched for gender and age group of 19 to 69 years. Magnetic Resonance Imaging were performed on a 3T scanner using different imaging techniques; structural 3D T1-weighted, fluid-attenuated inversion recovery, relaxometry with 5 echoes pulse sequence for T2 maps, magnetization transfer weighted and diffusion tensor imaging. The images were processed on different tools and were obtained results for the studies of diffusivity, volumetry, morphometry, tractometry, brain connectivity, and radiological findings of patients. Different statistical group analyses were performed in the quantitative results: 1) Parametric test for volumetry, tractometry and brain connectivity; 2) Parametric mapping for voxel morphometry; 3) Tract-based spatial statistics (TBSS) for diffusion coefficients. Changes were detected in all comparisons. In the patients, our main findings are: generalized loss brain volume more pronounced in periventricular regions associated with prominent ventricles, increased simultaneously perpendiculars and parallel diffusivity in the major tracts of the TBSS analyze, white matter density loss in the periventricular area, some bilateral trigeminal thickening, and general reduction of the brain connectivity. The CIDP affects the global brain and represents a demyelination in the CNS.

Negli ultimi 15 anni si è sviluppato un notevole interesse attorno all'analisi statistica di immagini MRI alla ricerca di alterazioni nei tessuti cerebrali. A tutt'oggi si hanno a disposizione diverse metodologie che permettono di studiare le differenze tra gruppi sia nella materia grigia che nella materia bianca. In particolare, per individuare atrofia nella materia grigia, è stata sviluppata una tecnica chiamata Voxel Based Morphometry (VBM). Questa tecnica è stata ampiamente utilizzata sia per caratterizzare diverse malattie di ordine neurodegenerativo, quali, ad esempio, Alzheimer e Parkinson sia per sottolineare sottili differenze strutturali tra pazienti sani raggruppati per differenti caratteristiche, quali sesso, destrorsi o mancini o più semplicemente per età. La tecnica VBM è stata applicata anche allo studio delle variazioni nelle mappe derivate da imaging di tipo DTI (VBM-DTI). Tuttavia, sono state sollevate obiezioni sulla reale precisione ed efficacia dei risultati ottenuti con l'analisi effettuata su questo tipo di dati. Sono state allora proposte diverse tecniche che tentassero di ovviare ai problemi sollevati dai ricercatori. Una tecnica in particolare, presentata nel 2006, Tract-based Spatial Statistics (TBSS), punta a dare una risposta precisa a tutte le obiezioni fino ad allora sollevate sull'analisi VBM applicata a dati DTI. A tutt'oggi è una tecnica ampiamente utilizzata e riconosciuta efficace nella caratterizzazione delle alterazioni cerebrali individuabili con lo studio delle metriche derivate da immagini DTI, quali Fractional Anisotropy (FA), Axial Diffusivity (AD), Radial Diffusivity (RD) e Apparent Diffusion Coefficient (ADC). In questo lavoro sono state mostrate le potenzialità dell'analisi VBM di immagini MR strutturali acquisite in topi, ratti e umani. Ci siamo concentrati sia su modelli traslazionali di multiple sclerosis (MS) e amyotrophic lateral sclerosis (ALS) sia su dati clinici provenienti da pazienti che hanno subito mild traumatic brain injuries (mTBI) derivanti da incidenti automobilistici, cadute o traumi derivanti da attività sportive. Abbiamo utilizzato il modello sperimentale Experimental Autoimmune Encephalomyelitis (EAE) come modello traslazionale per la MS e il modello murino SOD1(G93A) come modello traslazionale per la ALS. Nel modello sperimentale di Multiple Sclerosis ci siamo concentrati sull'identificazione, con tecnica VBM, di atrofia nella materia grigia corticale di ratti malati. Lo scopo finale era di correlarne i risultati con le analisi istologiche e i dati derivanti da MRI funzionale. Nella seconda parte di questa tesi abbiamo riportato i risultati di uno studio concentrato sulla definizione di biomarcatori in un modello sperimentale murino di amyotrophic lateral sclerosis. Il nostro scopo era di definire tramite MRI, utilizzando sia il VBM che tipi di imaging più tradizionali (basati su analisi di tipo region-based), diversi biomarcatori della malattia col fine ultimo di seguirne l'evoluzione per valutare l'efficacia di una terapia basata su cellule staminali. Nella terza e ultima parte, utilizzando la tecnica TBSS (e VBM-DTI), si è cercato di individuare biomarcatori specifici per gli eventi mTBI, per tentare di risolvere il problema del ritardato recupero delle capacità neurocognitive in pazienti mTBI. In questo lavoro si è cercato di correlare i risultati ottenuti con i dati derivanti dai test neurofisiologici, con lo scopo ultimo di meglio delineare la prognosi in pazienti che hanno subito traumi di tipo mTBI.