1,720,969 research outputs found
Visualization of evolving status epilepticus with diffusion and perfusion MR imaging
No full textAbstract Since Kojewnikoff's first description of epilepsia partialis continua, isolated case reports and small case series have elucidated the disease. However, few imaging studies have been performed. We report a case in which serial diffusion and perfusion MR imaging allowed monitoring of the changes in hemodynamic and cell membrane permeability until the resolution of clinical and electrical epileptic activity
The relationship between focal cortical thinning and white matter degeneration in patients with multiple sclerosis
No full textIntraoperative localization of subcortical brain lesions.
No full textBackground. Some brain tumors may grow immediately beneath the cortical surface without distorting its appearance. Intraoperative image guidance promotes safe resection. We have developed MRI-based corticotopography (MRI-bct), to localize lesions during surgery, using simple, non-dedicated equipment, to match a three-dimensional reconstruction with the corresponding appearance of the brain cortex.
Methods. Forty-six patients underwent resection of subcortical brain lesions, aided by MRI-bct. The lesions had a maximum diameter less than 3 cm, were subcortical but no deeper than the floor of the nearest cerebral sulcus. Each patient had a volumetric MRI scan with and without contrast administration. Data sets were transferred to a laptop personal computer and processed using a rendering software. At operation, the three-dimensional model of the brain, including a surface overlay of the lesion, was matched to the exposed brain surface. After its exact relationship with the overlying sulcal pattern was defined, the lesion was localized and resected. In selected patients, the procedure was coupled with functional brain mapping.
Results. Data processing took from 10 to 15 min and could be done whenever convenient before operation. Surface matching between the surgical field and the reformatted MRI always required less than 5 min and was done near the operating table. In all patients, the lesion was identified at the first attempt, through a small corticotomy, regardless of the brain shift after dural opening.
Conclusions. MRI-bct is a practical, time-saving neuronavigational aid ideal for localizing superficial lesions underlying the cerebral cortex because it unmistakably characterizes the adjacent sulcal anatomy
Diffusion tensor imaging in primary cervical dystonia
No full textBackground: It is the traditional view that primary dystonia arises from abnormal basal ganglia function but causes no apparent morphological changes. Objective: To determine whether cervical dystonia leads to ultrastructural changes in the brain, using diffusion tensor imaging to compare brain structure in 15 patients with cervical dystonia with 10 healthy controls. Design: Fractional anisotropy (FA) and mean diffusivity (MD) were obtained in 17 brain regions of interest. Results: Patients had higher FA values than controls in both putamina and lower FA values in the genu and in the body of the corpus callosum. Patients also had lower MD values in the left pallidum, the left putamen, and both caudati. Conclusions: In patients with cervical dystonia, diffusion tensor imaging shows ultrastructural changes in specific brain areas, including the basal ganglia
Diffusion tensor imaging in patients with primary cervical dystonia and in patients with blepharospasm
No full textDiffusion tensor imaging (DTI) analyses the movement of water molecules within the cerebral white matter thus providing information on ultrastructural brain changes. We studied 18 patients with cervical dystonia (CD), 16 with blepharospasm (BSP) and 35 years age-matched healthy controls. DTI data were obtained with a Philips 1.5 Tesla scanner and then processed to obtain maps of fractional anisotropy (FA) and mean diffusivity (MD). Twenty-three square regions of interest of uniform size were positioned on the FA maps and then automatically transferred to the MD maps. FA and MD values in the corpus callosum, left and right putamen, right caudate, left and right pre-frontal cortical area and left supplementary motor area in CD patients differed significantly from those in healthy controls. No significant regional differences were found between patients with BSP and healthy controls. In the CD group, age, duration and severity of dystonia did not correlate with regional FA/MD values, whereas the duration of botulinum toxin treatment correlated significantly with the MD value in the right-pre-frontal cortex. The abnormal DTI findings in patients with CD suggest the presence of brain ultrastructural changes in adult-onset primary CD. © 2008 The Author(s)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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