RESUMO
For the purpose of statistical characterization of the spatio-temporal correlation structure of brain functioning from high-dimensional fMRI time series, we introduce an innovation approach. This is based on whitening the data by the Nearest-Neighbors AutoRegressive model with external inputs (NN-ARx). Correlations between the resulting innovations are an extension of the usual correlations, in which mean-correction is carried out by the dynamic NN-ARx model instead of the static, standard linear model for fMRI time series. Measures of dependencies between regions are defined by summarizing correlations among innovations at several time lags over pairs of voxels. Such summarization does not involve averaging the data over each region, which prevents loss of information in case of non-homogeneous regions. Statistical tests based on these measures are elaborated, which allow for assessing the correlation structure in search of connectivity. Results of application of the NN-ARx approach to fMRI data recorded in visual stimuli experiments are shown. Finally, a number of issues related with its potential and limitations are commented.
Assuntos
Córtex Cerebral/anatomia & histologia , Córtex Cerebral/fisiologia , Simulação por Computador/normas , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Mapeamento Encefálico/métodos , Humanos , Vias Neurais/anatomia & histologia , Vias Neurais/fisiologia , Análise de Regressão , Fatores de Tempo , Percepção do Tato/fisiologia , Percepção Visual/fisiologiaRESUMO
We studied cranial magnetic resonance imaging (MRI) lesions in three women with acute attacks of recurrent longitudinally extensive transverse myelitis (r-LETM), recurrent-optic neuritis (r-ON) and r-LETM-CNS. Neuromyelitis Optica -immunoglobulin (IgG) antibody was positive in all cases. Brain MRI (1.5 Tesla) was performed according to protocol from consortium MS centre. We described the cranial lesions in brain MRI of acute relapses. These lesions were different from MS, most had an asymptomatic course which disappeared with time, protocol from consortium of MS centre criteria for brain MRI and seropositivity of NMO-IgG are useful tools for differentiate acute lesions of NMO/MS.
Assuntos
Encéfalo/patologia , Imageamento por Ressonância Magnética , Neuromielite Óptica/patologia , Doença Aguda , Adulto , Autoanticorpos/sangue , Feminino , Humanos , Imunoglobulina G/sangue , Neuromielite Óptica/imunologia , RecidivaRESUMO
OBJECTIVE: A computerized version of the Schaltenbrand and Wahren's stereotactic brain atlas for image-guided functional neurosurgery planning has been developed and integrated into our PC-based planning system. METHODS: The SW atlas plates were digitized, contoured and labeled for both hemispheres. The computerized atlas may be interactively registered with patient's data using linear and non-linear transformation. The implemented computational tools and applications are presented. RESULTS: Our computer system permits navigation through original or reconstructed slices, multiple-views synchronization and zoom to improve the localization of the commisures and the surgical targets, likewise the optimum path selection. Atlas position in the target's region can be interactively actualized and lesion's position and volume may be simulated. CONCLUSIONS: Its benefits of this approach include increased accuracy of target definition, decreased the number of electrode tracts and for instance the time of the surgery, and reduced surgical complications.
Assuntos
Mapeamento Encefálico/instrumentação , Encéfalo/anatomia & histologia , Encéfalo/cirurgia , Procedimentos Neurocirúrgicos/métodos , Cirurgia Assistida por Computador/instrumentação , HumanosRESUMO
AIM: The effectiveness of anatomic localization of the subthalamic nucleus (EAL) was assessed and the mapping method is described here. The symmetry of contralateral nuclei (SCN) was analyzed on 11 parkinsonian patients submitted to bilateral subthalamotomy with ablative lesioning. PATIENTS AND METHODS: To assess EAL the percentage so much of first trajectory (p1) as the total of trajectories (pt) that hit the target and the rest of subthalamic nucleus average distance (d) was calculated. The anatomic localization error (epsilon) is determined as a difference between first trajectory coordinates with those of medial determined nucleus point, through electrophysiological data as to the statistical significance of this error. SCN is analyzed by contrasting equality hypothesis at the nucleus maximum height alongside a trajectory, average electrophysiological position center and spatial distribution of all intranuclear recordings found in each hemisphere in all patients. RESULTS: The pi, pt and d obtained values were 86.36%, 86.13% and 1.41 +/- 1.01 mm respectively. The epsilon value was greater in anteroposterior direction of 1.11 +/- 0.83 mm without statistical significance. The average number of recorded trajectories for the first procedure was 6.45 and 6 for the second. The asymmetry of contralateral nucleus was not significant. CONCLUSIONS: An indirect method with CT brain images and a new electrophysiological mapping method with a multiunitary recording for first and second nucleus is safe enough and it yields a high effectiveness in anatomofunctional nucleus localization. The nucleus of a same patient are symmetrical. There is little space variability among patient non related to the differences in the intercommissural distance.
Assuntos
Mapeamento Encefálico , Técnicas Estereotáxicas , Núcleo Subtalâmico/anatomia & histologia , Idoso , Terapia por Estimulação Elétrica , Eletrodos Implantados , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doença de Parkinson/patologia , Doença de Parkinson/cirurgia , Núcleo Subtalâmico/cirurgiaRESUMO
To optimize spatial resolution in single photon emission tomography (SPET), it is essential to minimize the radius of rotation. In brain studies, different methods have been used to avoid shoulder interference when the radius of rotation is minimized: rectangular fields of view, modifications to the shielding around circular detectors and fan or cone beam collimators. However, few single-head systems can adopt these developments, particularly older cameras. A non-standard image acquisition method to reduce the radius of rotation in brain SPET with a single-head gamma camera is presented. The method applies a defined transformation to the original acquired images, maintaining the whole of the brain inside the field of view without shoulder interference and meeting the condition: pixel size < or = FWHM/3. With this method, it is possible to reduce the radius of rotation to 16 cm and to obtain a transaxial spatial resolution of 15.98 mm, which is 3.5 mm less than with the standard method used in our laboratory. This procedure was implemented for a Siemens Gammasonics ZLC 3700 gamma camera and has been validated in single-slice brain phantom studies. The method has the advantage of not requiring any complex or costly hardware.
Assuntos
Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Mapeamento Encefálico/instrumentação , Câmaras gama , Humanos , Imagens de Fantasmas , Rotação , Sensibilidade e Especificidade , Tomografia Computadorizada de Emissão de Fóton Único/instrumentaçãoRESUMO
The macrosomia is an obstetric eventuality associated to high maternal-fetal morbidity-mortality. This assay was planned in order to know the incidence of macrosomia in our institution, the relation between vaginal and abdominal deliveries and the fetal-maternal morbidity we reviewed 3590 records and we found 5.6% incidence of macrosomia in the global obstetric population. There was 58% of vaginal deliveries, 68% of the newborn were male. The main complications were in the C. sections, 2 laceration of the hysterectomy, and 2 peroperative atonias. In the vaginal deliveries, the lacerations of III and IV grade were 9 of each grade. The main fetal complications were 5 slight to severe asphyxia and 4 shoulder dystocias. This assay concludes that the macrosomia in our service is similar to the already published ones, a 42% were C. section and the maternal-fetal morbidity was low.
Assuntos
Asfixia Neonatal/etiologia , Macrossomia Fetal , Complicações do Trabalho de Parto/etiologia , Adolescente , Adulto , Peso ao Nascer , Cesárea , Distocia/etiologia , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Masculino , Pessoa de Meia-Idade , GravidezRESUMO
PIP: This article, based on personal experiences with a network of organizations of small and medium agricultural producers in Central America, aims to present the views of peasant organizations concerning agrarian problems in the region. The 3 major sections of work define the place of peasant agriculture in the traditional agrarian structure and the new problems resulting from the structural adjustment programs of the 1980s; separately describe the new peasant movements emerging in Honduras, El Salvador, Nicaragua, Costa Rica, and Panama, identifying common themes an efforts at international collaboration; and explore the positions of the peasant organizations on the optimal strategies for agricultural development and agrarian change. Agriculture remains the backbone of the Central American economies. But because the economic model in the region is 1 of accumulation characterized by dependency, concentration of capital, and social marginalization, the agrarian structure is at the basis of social tensions. Efforts to develop peasant agriculture and to give small producers access to marketing and credit services have been weak and sporadic. The new peasant movements are less inclined than those of the past to employ tactics of confrontation in their efforts to secure access to land and better working conditions. The new movement is the expression of small market producers sometimes grouped into associations who are oriented to production of basic foodstuffs for the internal market. A new concern with adaptation and negotiation is evident. The new organizations have in common a belief in their ability to propose new solutions to regional problems. Their views are founded on a positive assessment of the ability of peasant agriculture to produce food and add dynamism to the regional economy after barriers to credit, technological progress, and modernization in general are removed. Signs of increased cooperation are evident between peasant organizations and other groups representing the masses, and with other countries in the region. The positions of the peasant organizations call for access to lands for small proprietors as well as landless agricultural laborers, and for new forms of organizing production that will respect the conservation and development of natural resources.^ieng