RESUMO
PURPOSE: A feasibility study of an echo-planar spectroscopic imaging (EPSI) using a short echo time (TE) that trades off sensitivity, compared with other short-TE methods, to achieve whole brain coverage using inversion recovery and spatial oversampling to control lipid bleeding. METHODS: Twenty subjects were scanned to examine intersubject variance. One subject was scanned five times to examine intrasubject reproducibility. Data were analyzed to determine coefficients of variance (COV) and intraclass correlation coefficient (ICC) for N-acetylaspartate (NAA), total creatine (tCr), total choline (tCho), glutamine/glutamate (Glx), and myo-inositol (mI). Regional metabolite concentrations were derived by using multi-voxel analysis based on lobar-level anatomic regions. RESULTS: For whole-brain mean values, the intrasubject COVs were 14%, 15%, and 20% for NAA, tCr, and tCho, respectively, and 31% for Glx and mI. The intersubject COVs were up to 6% higher. For regional distributions, the intrasubject COVs were ≤ 5% for NAA, tCr, and tCho; ≤ 9% for Glx; and ≤15% for mI, with about 6% higher intersubject COVs. The ICCs of 5 metabolites were ≥ 0.7, indicating the reliability of the measurements. CONCLUSION: The present EPSI method enables estimation of the whole-brain metabolite distributions, including Glx and mI with small voxel size, and a reasonable scan time and reproducibility.
Assuntos
Algoritmos , Encéfalo/metabolismo , Imageamento por Ressonância Magnética/métodos , Imagem Molecular/métodos , Espectroscopia de Prótons por Ressonância Magnética/métodos , Adulto , Ácido Aspártico/análogos & derivados , Ácido Aspártico/metabolismo , Encéfalo/anatomia & histologia , Colina/metabolismo , Creatina/metabolismo , Feminino , Ácido Glutâmico/metabolismo , Glutamina/metabolismo , Humanos , Inositol/metabolismo , Masculino , Modelos Biológicos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Distribuição TecidualRESUMO
Structural brain imaging parameters may successfully predict cognitive performance in neurodegenerative diseases but mostly fail to predict cognitive abilities in healthy older adults. One important aspect contributing to this might be sex differences. Behaviorally, older males and females have been found to differ in terms of cognitive profiles, which cannot be captured by examining them as one homogenous group. In the current study, we examined whether the prediction of cognitive performance from brain structure, i.e. region-wise grey matter volume (GMV), would benefit from the investigation of sex-specific cognitive profiles in a large sample of older adults (1000BRAINS; N = 634; age range 55-85 years). Prediction performance was assessed using a machine learning (ML) approach. Targets represented a) a whole-sample cognitive component solution extracted from males and females, and b) sex-specific cognitive components. Results revealed a generally low predictability of cognitive profiles from region-wise GMV. In males, low predictability was observed across both, the whole sample as well as sex-specific cognitive components. In females, however, predictability differences across sex-specific cognitive components were observed, i.e. visual working memory (WM) and executive functions showed higher predictability than fluency and verbal WM. Hence, results accentuated that addressing sex-specific cognitive profiles allowed a more fine-grained investigation of predictability differences, which may not be observable in the prediction of the whole-sample solution. The current findings not only emphasize the need to further investigate the predictive power of each cognitive component, but they also emphasize the importance of sex-specific analyses in older adults.
Assuntos
Encéfalo , Função Executiva , Feminino , Humanos , Masculino , Idoso , Idoso de 80 Anos ou mais , Encéfalo/diagnóstico por imagem , Cognição , Substância Cinzenta/diagnóstico por imagem , Memória de Curto PrazoRESUMO
Differences in brain structure and functional and structural network architecture have been found to partly explain cognitive performance differences in older ages. Thus, they may serve as potential markers for these differences. Initial unimodal studies, however, have reported mixed prediction results of selective cognitive variables based on these brain features using machine learning (ML). Thus, the aim of the current study was to investigate the general validity of cognitive performance prediction from imaging data in healthy older adults. In particular, the focus was with examining whether (1) multimodal information, i.e., region-wise grey matter volume (GMV), resting-state functional connectivity (RSFC), and structural connectivity (SC) estimates, may improve predictability of cognitive targets, (2) predictability differences arise for global cognition and distinct cognitive profiles, and (3) results generalize across different ML approaches in 594 healthy older adults (age range: 55-85 years) from the 1000BRAINS study. Prediction potential was examined for each modality and all multimodal combinations, with and without confound (i.e., age, education, and sex) regression across different analytic options, i.e., variations in algorithms, feature sets, and multimodal approaches (i.e., concatenation vs. stacking). Results showed that prediction performance differed considerably between deconfounding strategies. In the absence of demographic confounder control, successful prediction of cognitive performance could be observed across analytic choices. Combination of different modalities tended to marginally improve predictability of cognitive performance compared to single modalities. Importantly, all previously described effects vanished in the strict confounder control condition. Despite a small trend for a multimodal benefit, developing a biomarker for cognitive aging remains challenging.
Assuntos
Encéfalo , Imageamento por Ressonância Magnética , Imageamento por Ressonância Magnética/métodos , Encéfalo/diagnóstico por imagem , Neuroimagem , Cognição , Aprendizado de MáquinaRESUMO
The angular gyrus (AG) has been associated with multiple cognitive functions, such as language, spatial and memory functions. Since the AG is thought to be a cross-modal hub region suffering from significant age-related structural atrophy, it may also play a key role in age-related cognitive decline. However, the exact relation between structural atrophy of the AG and cognitive decline in older adults is not fully understood, which may be related to two aspects: First, the AG is cytoarchitectonically divided into two areas, PGa and PGp, potentially sub-serving different cognitive functions. Second, the older adult population is characterized by high between-subjects variability which requires targeting individual phenomena during the aging process. We therefore performed a multimodal (gray matter volume [GMV], resting-state functional connectivity [RSFC] and structural connectivity [SC]) characterization of AG subdivisions PGa and PGp in a large older adult population, together with relations to age, cognition and lifestyle on the group level. Afterwards, we switched the perspective to the individual, which is especially important when it comes to the assessment of individual patients. The AG can be considered a heterogeneous structure in of the older brain: we found the different AG parts to be associated with different patterns of whole-brain GMV associations as well as their associations with RSFC, and SC patterns. Similarly, differential effects of age, cognition and lifestyle on the GMV of AG subdivisions were observed. This suggests each region to be structurally and functionally differentially involved in the older adult's brain network architecture, which was supported by differential molecular and genetic patterns, derived from the EBRAINS multilevel atlas framework. Importantly, individual profiles deviated considerably from the global conclusion drawn from the group study. Hence, general observations within the older adult population need to be carefully considered, when addressing individual conditions in clinical practice.
Assuntos
Mapeamento Encefálico , Imageamento por Ressonância Magnética , Humanos , Idoso , Encéfalo/diagnóstico por imagem , Cognição , Lobo ParietalRESUMO
PURPOSE: To present some unusual MR findings in a group of patients from the south-west of the Dominican Republic suffering from Pantothenate Kinase Associated Neurodegeneration (PKAN). MATERIALS AND METHODS: Twenty patients and one preclinical case homozygous for the PANK2 mutation, 13 heterozygous gene carriers and 14 healthy volunteers were scanned prospectively using a 3 Tesla system. RESULTS: All patients showed the typical signal reduction within the globus pallidus and the substantia nigra. A surprising finding was the absence of the bright spot ("tiger's eye") in the medial part of the pallidum in 6 patients, but not in the preclinical case. Both fractional anisotropy (FA) and mean diffusivity (MD) were increased with high significance in the globus pallidus, whereas a reduction of FA in the anterior parts of the internal capsule was accompanied by an elevation of MD. CONCLUSION: Our findings support the hypothesis that the absence of the "tiger's eye" in PKAN might be secondary, probably caused by an increased accumulation of iron. This could artificially increase FA and MD values and change fiber tracking results. Except for the fronto-basal tracts, white matter was preserved well. This encouraging finding might support efforts to develop further therapeutic strategies in this devastating dystonia.
Assuntos
Encéfalo/patologia , Heterozigoto , Imageamento por Ressonância Magnética/métodos , Mutação de Sentido Incorreto/genética , Neurodegeneração Associada a Pantotenato-Quinase/genética , Neurodegeneração Associada a Pantotenato-Quinase/patologia , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Adolescente , Adulto , Idoso , Criança , Feminino , Predisposição Genética para Doença/genética , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Adulto JovemRESUMO
Inattention is the most important behavioral feature of adult patients with attention-deficit/hyperactivity disorder (ADHD). Neuroimaging studies in ADHD have demonstrated abnormalities primarily in the frontostriatal circuitry and were mostly conducted in children. We investigated white matter (WM) integrity in adult ADHD patients and the correlation of WM microstructure and neuropsychological parameters in 37 (21 men) never-medicated adult ADHD patients and 34 age- and gender-matched healthy controls. All subjects underwent clinical interviews, rating scales, and neuropsychological tests of attentional performance. Diffusion tensor imaging (DTI) was acquired, and 12 WM regions-of-interest (ROIs) within the attentional network were chosen. Group differences of mean fractional anisotropy (FA) and mean diffusivity (MD) values were calculated for each ROI, and patients' DTI measures were then correlated with measures of attentional performance. FA values in ADHD patients were significantly reduced in the left inferior longitudinal fasciculus (ILF), while MD values were significantly increased in ADHD patients in the frontal portion of the left frontooccipital fasciculus (IFO). In ADHD patients, MD values were negatively correlated with attentional performance in the left ILF. Our findings provide further support for disturbed frontostriatal structural connectivity and also point to an involvement of the left temporal white matter with an impact on attentional performance.
Assuntos
Transtorno do Deficit de Atenção com Hiperatividade , Atenção/fisiologia , Corpo Estriado , Imagem de Tensor de Difusão/métodos , Lobo Frontal , Lobo Temporal , Adulto , Anisotropia , Transtorno do Deficit de Atenção com Hiperatividade/diagnóstico , Transtorno do Deficit de Atenção com Hiperatividade/fisiopatologia , Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Corpo Estriado/patologia , Corpo Estriado/fisiopatologia , Difusão , Feminino , Lobo Frontal/patologia , Lobo Frontal/fisiopatologia , Humanos , Masculino , Fibras Nervosas Mielinizadas/patologia , Vias Neurais/patologia , Vias Neurais/fisiopatologia , Testes Neuropsicológicos , Escalas de Graduação Psiquiátrica , Lobo Temporal/patologia , Lobo Temporal/fisiopatologiaRESUMO
Fiber tracking is a technique that, based on a diffusion tensor magnetic resonance imaging dataset, locates the fiber bundles in the human brain. Because it is a computationally expensive process, the interactivity of current fiber tracking tools is limited. We propose a new approach, which we termed real-time interactive fiber tracking, which aims at providing a rich and intuitive environment for the neuroradiologist. In this approach, fiber tracking is executed automatically every time the user acts upon the application. Particularly, when the volume of interest from which fiber trajectories are calculated is moved on the screen, fiber tracking is executed, even while it is being moved. We present our fiber tracking tool, which implements the real-time fiber tracking concept by using the video card's graphics processing units to execute the fiber tracking algorithm. Results show that real-time interactive fiber tracking is feasible on computers equipped with common, low-cost video cards.
Assuntos
Encéfalo/anatomia & histologia , Gráficos por Computador , Imagem de Difusão por Ressonância Magnética/métodos , Processamento de Imagem Assistida por Computador/métodos , Fibras Nervosas Mielinizadas , Algoritmos , Estudos de Viabilidade , HumanosRESUMO
OBJECTIVE: To correlate the CT imaging findings of the visibility and size of the vestibular aqueduct (VA) with the degree of the cochlear hydrops determined in MRI late imaging of the hydrops. Study Design: Retrospective study. Setting: Tertiary referral center. Patients: A total of 127 patients (62 women, 65 men, average age 55.6âyrs): 86 of these were diagnosed with Menière's disease (American Academy of Otolaryngology-Head and Neck Surgery [AAO-HNS] criteria; 67 unilateral, 19 bilateral). INTERVENTIONS: Temporal bone CT and hydrops MRI were performed in all patients. MAIN OUTCOME MEASURES: Visibility/width of the VA in temporal bone CT and grade of cochlear hydrops evaluated by MRI. RESULTS: The width of the VA is significantly smaller in patients diagnosed with Menière's disease (30% non-visible VA), compared with the patients who did not fulfill the diagnostic criteria of Menière's disease (12% non-visible VA) (double sided Spearman correlation, pâ<â0.001). In all ears of patients diagnosed with Menière's disease the width of the VA was significantly correlated with the degree of the cochlear hydrops (in cases of non-visible VA 65% [34/52] ears presented with hydrops grade 3 or 4; 13% [7/52] ears presented with hydrops grade 1 or 2 and 21% [11/52] ears showed no hydrops) (Spearman correlation pâ=â0.001/pâ<â0.01). This is also true for all ears that can be summarized as hydrophic ear disease (symptomatic ears that present with a hydrops in MRI). CONCLUSIONS: The results of our study could confirm the importance of the VA in the pathogenesis of the endolymphatic hydrops in vivo.
Assuntos
Hidropisia Endolinfática , Doença de Meniere , Aqueduto Vestibular , Edema/complicações , Edema/patologia , Hidropisia Endolinfática/complicações , Hidropisia Endolinfática/diagnóstico por imagem , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Doença de Meniere/complicações , Doença de Meniere/diagnóstico por imagem , Pessoa de Meia-Idade , Estudos Retrospectivos , Aqueduto Vestibular/diagnóstico por imagem , Aqueduto Vestibular/patologiaRESUMO
PURPOSE: Evaluating the extent of cerebral ischemic infarction is essential for treatment decisions and assessment of possible complications in patients with acute ischemic stroke. Patients are often triaged according to image-based early signs of infarction, defined by Alberta Stroke Program Early CT Score (ASPECTS). Our aim was to evaluate interrater reliability in a large group of readers. METHODS: We retrospectively analyzed 100 investigators who independently evaluated 20 non-contrast computed tomography (NCCT) scans as part of their qualification program for the TENSION study. Test cases were chosen by four neuroradiologists who had previously scored NCCT scans with ASPECTS between 0 and 8 and high interrater agreement. Percent and interrater agreements were calculated for total ASPECTS, as well as for each ASPECTS region. RESULTS: Percent agreements for ASPECTS ratings was 28%, with interrater agreement of 0.13 (95% confidence interval, CI 0.09-0.16), at zero tolerance allowance and 66%, with interrater agreement of 0.32 (95%â¯CI: 0.21-0.44), at tolerance allowance set by TENSION inclusion criteria. ASPECTS region with highest level of agreement was the insular cortex (percent agreementâ¯= 96%, interrater agreementâ¯= 0.96 (95%â¯CI: 0.94-0.97)) and with lowest level of agreement the M3 region (percent agreementâ¯= 68%, interrater agreementâ¯= 0.39 [95%â¯CI: 0.17-0.61]). CONCLUSION: Interrater agreement reliability for total ASPECTS and study enrollment was relatively low but seems sufficient for practical application. Individual region analysis suggests that some are particularly difficult to evaluate, with varying levels of reliability. Potential impairment of the supraganglionic region must be examined carefully, particularly with respect to the decision whether or not to perform mechanical thrombectomy.
Assuntos
Isquemia Encefálica , Acidente Vascular Cerebral , Alberta , Isquemia Encefálica/diagnóstico por imagem , Humanos , Córtex Insular , Variações Dependentes do Observador , Reprodutibilidade dos Testes , Estudos Retrospectivos , Acidente Vascular Cerebral/diagnóstico por imagemRESUMO
UNLABELLED: Central nervous system involvement is a major burden in Fabry disease. Conventional cranial magnetic resonance imaging (MRI) shows micro- and macroangiopathic changes such as severe and progressive white matter lesions (WMLs) at an early age on T2- and fluid-attenuated inversion recovery-weighted images, increased signal intensity in the pulvinar on T1-weighted MRI, as well as tortuosity and dilatation of the larger vessels (dolicho-ectasia). Using diffusion tensor imaging (DTI), a new structural MRI-technique that measures water diffusion characteristics, we showed marked brain tissue alterations in Fabry disease predominantly in the periventricular white matter. Even patients with few WMLs had significantly elevated brain tissue diffusivity. CONCLUSION: DTI is more sensitive in detecting brain tissue changes in Fabry disease than conventional MRI. DTI measurements could provide appropriate surrogate parameters with which to monitor the natural history of structural brain involvement and potential effects of therapy (such as enzyme replacement) in Fabry disease.
Assuntos
Encéfalo/patologia , Doença de Fabry/patologia , Encéfalo/fisiopatologia , Circulação Cerebrovascular/fisiologia , Imagem de Difusão por Ressonância Magnética , Doença de Fabry/fisiopatologia , Deslocamentos de Líquidos Corporais/fisiologia , HumanosRESUMO
Fabry disease (FD) is a lysosomal storage disorder that is associated with marked cerebrovascular disease. Conventional MRI shows a progressive load of white matter lesions (WMLs) due to cerebral vasculopathy in the course of FD. To quantify brain structural changes in clinically affected male and female patients with FD we performed a prospective Diffusion-Tensor Imaging (DTI) study in 27 adult Fabry patients (13m, 14f) and 21 age-matched controls (12 m, 9f). Global Mean Diffusivity (MD) was increased in FD (P = 0.003) whereas global Fractional Anisotropy (FA) did not differ significantly between FD and controls. Even FD patients without significant WMLs (9m, 9f) showed increased global MD (P = 0.004). Regions of interest with significant MD elevations were located in the frontal, parietal and temporal white matter. No differences of thalamic and hippocampal DTI measurements could be detected between FD and controls. DTI parameters did not differ between male and female patients. The data provide the first evidence of a pattern of marked structural brain tissue alterations in adult FD male and female patients even without WMLs. DTI seems to be an appropriate diagnostic tool to quantify brain tissue integrity in FD. Moreover, this method could be favorable for longitudinal assessment of brain structure alterations in FD, and for monitoring the cerebral effects of enzyme replacement therapy.
Assuntos
Encéfalo/patologia , Imagem de Difusão por Ressonância Magnética , Doença de Fabry/patologia , Doença de Fabry/fisiopatologia , Plasticidade Neuronal/fisiologia , Adulto , Mapeamento Encefálico , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Fatores SexuaisRESUMO
In our prospective study of diffusion tensor imaging (DTI), we measured hippocampal mean diffusivity (MD) and volumes in amnestic mild cognitive impairment (MCI). Thirteen MCI patients were followed-up by clinical assessment over a mean 112-year period. MCI patients who converted to dementia (6 of 13) during the observation period had slightly elevated left hippocampal mean diffusivity at baseline compared with MCI patients who remained clinically stable. Hippocampal volumes as well as baseline verbal memory and MMSE did not differ significantly between stable MCI patients and converters. Hippocampal diffusivity was superior to hippocampal volumes for prediction of conversion to dementia in MCI patients during a 112-year period.
Assuntos
Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/epidemiologia , Demência/epidemiologia , Imagem de Difusão por Ressonância Magnética/métodos , Hipocampo/anatomia & histologia , Hipocampo/fisiopatologia , Idoso , Feminino , Humanos , Masculino , Testes Neuropsicológicos , Valor Preditivo dos Testes , Estudos Prospectivos , Índice de Gravidade de DoençaRESUMO
Different processes like microvascular dysfunction, free radical toxicity, beta-amyloid deposits, and Wallerian degeneration can cause functionally relevant disturbances of cerebral neuronal networks by myelin degeneration. Color-coded diffusion-tensor-imaging (ccDTI) allows the structural identification and quantification of myelinated fiber tracts. Particularly, posterior cingulate fiber tracts, which are regarded as important neuronal substrates of the network representing memory processing can be localized only imprecisely by conventional magnetic resonance imaging techniques. The posterior cingulate bundles were assessed by ccDTI in 17 patients with amnestic mild cognitive impairment (MCI), 25 patients with Alzheimer's dementia (DAT), and 21 age-matched controls. Additionally, DTI values were correlated with memory performance in the delayed verbal recall test. Fractional anisotropy and mean diffusivity differed significantly between MCI and controls, as well as between DAT and controls. Performance in the delayed verbal recall test of the entire study group correlated significantly with posterior cingulate bundle anisotropy and diffusivity. Using ccDTI seems, hence, a favorable strategy to detect and quantify the structural integrity of posterior cingulate white matter in MCI. Alterations of DTI parameters substantiate the involvement of white matter pathology in the development of MCI. Moreover, ccDTI could serve as in vivo method to investigate age and disease-related myelin alterations as potential morphological substrates of cognitive dysfunction.
Assuntos
Doença de Alzheimer/patologia , Transtornos Cognitivos/patologia , Imagem de Difusão por Ressonância Magnética/métodos , Giro do Cíngulo/patologia , Vias Neurais/patologia , Idoso , Doença de Alzheimer/fisiopatologia , Anisotropia , Transtornos Cognitivos/fisiopatologia , Imagem de Difusão por Ressonância Magnética/instrumentação , Feminino , Giro do Cíngulo/fisiopatologia , Hipocampo/fisiopatologia , Humanos , Processamento de Imagem Assistida por Computador/instrumentação , Processamento de Imagem Assistida por Computador/métodos , Masculino , Transtornos da Memória/patologia , Transtornos da Memória/fisiopatologia , Transtornos da Memória/psicologia , Pessoa de Meia-Idade , Fibras Nervosas Mielinizadas/patologia , Vias Neurais/fisiopatologia , Testes Neuropsicológicos , Valor Preditivo dos TestesRESUMO
Recent neuroanatomical and functional neuroimaging studies indicate that the anterior part of the hippocampus, rather than the whole structure, may be specifically involved in episodic memory. In the present work, we examined whether anterior structural measurements are superior to other regional or global measurements in mapping functionally relevant degenerative alterations of the hippocampus in Alzheimer's disease (AD). Twenty patients with early AD (MMSE 25.7+/-1.7) and 18 healthy controls were studied using magnetic resonance and diffusion-tensor imaging. Using a regions-of-interest analysis, we obtained volumetric and diffusivity measures of the hippocampal head and body-tail-section as well as of the whole hippocampus. Detailed cognitive evaluation was based on the CERAD battery. All volumetric measures as well as diffusivity of the hippocampus head were significantly (p<0.01) altered in patients as compared to controls. In patients, increased left head diffusivity significantly (p<0.01) correlated with performance on free delayed verbal recall test (DVR) (r=-0.74, p=0.0002) and with the CERAD global score. Reduced volume of the left body-tail was also associated with performance on DVR (r=0.62, p=0.004). Stepwise regression analyses revealed that increased left head diffusivity was the only predictor for performance on DVR (R(2)=52%, p<0.0005). These findings suggest that anterior hippocampus diffusivity is more closely related to verbal episodic memory impairment than other regional or global structural measures. Our data support the hypothesis of functional differentiation in general and the specific role of the anterior hippocampus in episodic memory in particular. Diffusivity measurements might be highly sensitive to functionally relevant degenerative alterations of the hippocampus.
Assuntos
Doença de Alzheimer/epidemiologia , Doença de Alzheimer/fisiopatologia , Hipocampo/fisiopatologia , Transtornos da Memória/epidemiologia , Transtornos da Memória/fisiopatologia , Rememoração Mental , Idade de Início , Idoso , Atrofia/epidemiologia , Atrofia/patologia , Atrofia/fisiopatologia , Feminino , Hipocampo/patologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Transtornos da Memória/diagnóstico , Valor Preditivo dos TestesRESUMO
PURPOSE: To look for the presence and age-dependence of late structural alterations of otherwise normal-appearing cerebral gray and white matter after radiation and chemotherapy in adult survivors of acute lymphoblastic leukemia (ALL) during childhood. MATERIALS AND METHODS: In a group of 13 adult survivors 17-37 years old, who had been treated by total brain radiation (18-24 Gy) and chemotherapy 16-28 years ago, prospective MR examinations including diffusion tensor imaging (DTI) were performed. Evaluation included volumetry, calculation of mean diffusivity (MD) and fractional anisotropy (FA), and comparison of results to an age-matched control group. RESULTS: DTI showed significantly reduced FA values in the temporal lobes (difference of 0.069 units, P < 0.001), hippocampi (difference of 0.033 units, P < 0.001), and thalami (difference of 0.046 units, P = 0.001), which were accompanied by significant white matter volume loss (difference of 92 cm(3), P < 0.001). Significant elevations of MD were limited to the temporal white matter (difference of 42 x 10(-6) mm(2)/s, P = 0.005). Global and frontal white matter MD correlated negatively to increasing age of the survivors (P < 0.01). CONCLUSION: With regard to structural white matter alterations, adult long-term survivors of childhood ALL, who had received total brain radiation and chemotherapy, apparently show the same overall age dependence as controls. Follow-up studies are needed for confirmation.
Assuntos
Encéfalo/patologia , Irradiação Craniana/efeitos adversos , Leucemia/tratamento farmacológico , Leucemia/radioterapia , Imageamento por Ressonância Magnética/métodos , Sobreviventes/estatística & dados numéricos , Adolescente , Adulto , Distribuição por Idade , Anisotropia , Mapeamento Encefálico/métodos , Estudos de Casos e Controles , Difusão , Imagem de Difusão por Ressonância Magnética/métodos , Feminino , Humanos , MasculinoRESUMO
PURPOSE: To differentiate fibroblastic meningiomas, usually considered to be of a hard consistency, from other benign subtypes using diffusion tensor imaging (DTI). MATERIALS AND METHODS: From DTI data sets of 30 patients with benign meningiomas, we calculated diffusion tensors and mean diffusivity (MD) and fractional anisotropy (FA) maps as well as barycentric maps representing the geometrical shape of the tensors. The findings were compared to postoperative histology. The study was approved by the local ethics committee, and informed consent was given by the patients. RESULTS: According to one-way analysis of variance (ANOVA), FA was the best parameter to differentiate between the subtypes (F=32.2; p<0.0001). Regarding tensor shape, endothelial meningiomas were represented by spherical tensors (80%) corresponding to isotropic diffusion, whereas the fibroblastic meningiomas showed a high percentage (43%) of nonspherical tensors, indicating planar or longitudinal diffusion. The difference was highly significant (F=28.4; p<0.0001) and may be due to the fascicular arrangement of long spindle-shaped tumor cells and the high content of intra- and interfascicular fibers as shown in the histology. In addition, a capsule-like rim of the in-plane diffusion surrounded most meningiomas irrespective of their histological type. CONCLUSION: If these results correlate to the intraoperative findings of meningioma consistency, DTI-based measurement of FA and analysis of the shape of the diffusion tensor is a promising method to differentiate between fibroblastic and other subtypes of benign meningiomas in order to get information about their "hard" or "soft" consistency prior to removal.
Assuntos
Imagem de Difusão por Ressonância Magnética , Neoplasias Meníngeas/diagnóstico , Meningioma/diagnóstico , Adulto , Idoso , Idoso de 80 Anos ou mais , Análise de Variância , Anisotropia , Diagnóstico Diferencial , Feminino , Fibroblastos , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Neoplasias Meníngeas/patologia , Meningioma/patologia , Pessoa de Meia-Idade , SoftwareRESUMO
Hippocampus atrophy is a frequent finding in mild cognitive impairment (MCI), whereas diffusion-tensor-imaging (DTI) has demonstrated its value to detect subtle brain tissue changes in several neuropsychiatric diseases including MCI. To compare the diagnostic accuracy of both methods, high resolution MRI scans for hippocampus volumetry, and co-registered DTI-scans for ROI-based mean diffusivity (MD) and fractional anisotropy (FA) were carried out in 18 patients with amnestic MCI (7 females, age 67.3+/-8.7 years, MMSE 25.2+/-2.2) and 18 controls (age 66.9+/-9.0 years, MMSE 28.7+/-1.0). Diagnostic properties of normalized hippocampus volume (HV) and DTI measures with regard to MCI status were estimated by receiver operating characteristics (ROC) analyses and logistic regression. Parameters of the left hippocampus showed superior predictive power when compared to the right. At a specificity set to 80%, left HV had low sensitivity (50%); left hippocampal MD values revealed superior sensitivity (89%), similar to left hippocampal FA (78%). The results demonstrate higher sensitivity of DTI-derived left hippocampal parameters than volume measures in detecting subtle hippocampal abnormalities related to MCI.
Assuntos
Amnésia/diagnóstico , Amnésia/fisiopatologia , Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/fisiopatologia , Imagem de Difusão por Ressonância Magnética/métodos , Hipocampo/patologia , Idoso , Análise de Variância , Estudos de Casos e Controles , Feminino , Lateralidade Funcional , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Curva ROC , Reprodutibilidade dos TestesRESUMO
Fiber tracking allows the in vivo reconstruction of human brain white matter fiber trajectories based on magnetic resonance diffusion tensor imaging (MR-DTI), but its application in the clinical routine is still in its infancy. In this study, we present a new software for fiber tracking, developed on top of a general-purpose DICOM (digital imaging and communications in medicine) framework, which can be easily integrated into existing picture archiving and communication system (PACS) of radiological institutions. Images combining anatomical information and the localization of different fiber tract trajectories can be encoded and exported in DICOM and Analyze formats, which are valuable resources in the clinical applications of this method. Fiber tracking was implemented based on existing line propagation algorithms, but it includes a heuristic for fiber crossings in the case of disk-shaped diffusion tensors. We successfully performed fiber tracking on MR-DTI data sets from 26 patients with different types of brain lesions affecting the corticospinal tracts. In all cases, the trajectories of the central spinal tract (pyramidal tract) were reconstructed and could be applied at the planning phase of the surgery as well as in intraoperative neuronavigation.
Assuntos
Mapeamento Encefálico/métodos , Neoplasias Encefálicas/diagnóstico , Imagem de Difusão por Ressonância Magnética/métodos , Interpretação de Imagem Assistida por Computador/métodos , Fibras Nervosas Mielinizadas/patologia , Tratos Piramidais/patologia , Software , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Anisotropia , Neoplasias Encefálicas/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , RadiografiaRESUMO
Hippocampal atrophy has been related to mild cognitive impairment (MCI) and early Alzheimer disease (AD), but the diagnostic significance of cross-sectionally determined hippocampal volumes is still ambiguous. Diffusion-Tensor-Imaging (DTI) in MCI patients revealed an association of microstructural changes in hippocampal areas with verbal memory decline. MRI volumetry and DTI were combined to investigate 18 MCI patients attending a memory clinic, and 18 carefully age- and gender-matched healthy controls. Neuropsychological testing, high resolution T1-weighted volume MRI scans, and DTI scans with regions-of-interest in hippocampal areas were applied. Left hippocampal volume was significantly lower (-11%, P = 0.02) in MCI patients than in control subjects. No significant differences were found for the right hippocampus (-4%). Mean diffusivity (MD) was significantly elevated in MCI patients vs. controls in left (+10%, P = 0.002) and right hippocampal areas (+13%, P = 0.02). Hippocampal volume and MD values were not significantly correlated. Combining left hippocampal volume and MD measures showed that lower left hippocampal volumes were associated with poor verbal memory performance particularly when co-occurring with high MD values. No comparable associations could be found regarding the right hippocampal formation and with respect to non-verbal memory function. The results demonstrate that microstructural abnormalities as revealed by DTI are very sensitive early indicators of hippocampal dysfunction. The combination of macro- and microstructural parameters in hippocampal areas could be promising in early detection of neurodegenerative processes.