1,720,958 research outputs found
Fusion imaging technology of the intracranial veins.
No full textOBJECTIVES: Fusion imaging technology (FIT) combines different imaging techniques by means of properly designed software. The aim of this study was to validate the ultrasonographic representation of intracranial vein anatomy by combining transcranial echo-colour Doppler (TECD) with conventional magnetic resonance imaging (MRI). In addition, we investigated the possibility of insonating the veins of the base of the skull through the novel condylar window. METHODS: We examined venous brain circulation in five healthy subjects by means of FIT, using a 1.5 T MR scanner and an ultrasound TECD equipped with Virtual Navigator technology.Results and conclusionsInsonation of the Rosenthal and other intracranial veins through the classical transtemporal window, based on anatomical assumption, but never before validated by means of FIT study, was confirmed. Moreover, in all five subjects, FIT demonstrated the possibility of insonating the petrosal sinuses and the cavernous sinus area through the novel transcondylar approach. In conclusion, the feasibility of FIT of the intracranial veins potentially permits to study subjects in different postures and/or at the bed of non-transportable patients, after the initial MRI acquisition. Finally, the novel transcondylar approach allows obtaining haemodynamic information from the cavernous and the petrosal sinuses usually not investigated by TECD alone
'Venous insufficiency' is not the cause of multiple sclerosis (MS) (but it could be a risk factor for MS and for different brain disorders).
Full text linkIn the last four years several studies have been conducted and many articles have been published on the possible role of venous insufficiency in multiple sclerosis (MS).
In a preliminary study, published in 2007 by Zamboni et al., 89 MS patients and 60 healthy subjects were investigated using the transcranial color-coded duplex sonography technique and it was found that hemodynamic alterations of brain venous drainage were significantly more frequent in MS patients than in controls ( 1 ) .
Zamboni et al. ( 2 ) continued their research and in a later study, they investigated 65 MS patients and 235 controls using transcranial and extracranial color Doppler and selective extracranial venography targeting the internal jugular and azygos veins. They found that all MS patients had evidence of multiple extracranial venous stenosis compared with the stenosis-free controls. This functional and/or anatomical venous abnormality defined by the presence of at least two of five Doppler criteria was named chronic cerebrospinal venous insufficiency (CCSVI). CCSVI is characterised by multiple stenoses of the extracranial venous drainage pathways, i.e. the internal jugular veins and the azygos veins, with flow alterations and collateral formation. A consequent failure of the blood-brain barrier and CNS accumulation of iron have been postulated, which could trigger and maintain the autoimmune cascade in MS ( 1 – 3 ) .
Quickly, the news of a ‘new theory’ on MS etiology, implying possible therapeutic ‘liberation’ interventions, spread from the scientific context to patient organisations and to the general public. Websites, Facebook pages, blogs and other social network media promoted the venous theory. Thousands of MS patients worldwide were submitted to venous angioplasty outside controlled scientific contexts and before the actual prevalence and the biological meaning of CCSVI had been clearly established.
Over the past couple of years, several groups have published further research into CCSVI, the results of their studies showing considerable discrepancies and significant differences in the prevalence of CCSVI between MS patients and controls ( 4 – 9 ) .
The high prevalence of CCSVI in MS patients observed by Zamboni and colleagues has been confirmed by other independent groups ( 4 – 6 ) , but at the same time, several other authors were unable to document the presence of extracranial venous stenosis using the same or other methodologies ( 7 – 9 ) . As a result, currently there is not even a general consensus on the actual existence of the phenomenon. Unfortunately, even part of the scientific community seemed, on occasions, to abandon the lay position and divided, in a rather fideistic manner, into ‘pro-CCSVI’ and ‘anti-CCSVI ‘factions.
Recently, we had the opportunity to perform an international multicenter study on CCSVI, collecting the largest sample of MS patients yet published ( 10 ) . Despite great between-center differences in CCSVI figures (suggesting that assessing techniques should be improved), we found consistent associations between CCSVI and MS phenotype. The type of associations found (older age at onset and greater disease severity in CCSVI-positive subjects) suggested to us that CCSVI may act on MS as a ‘risk factor’ in a multifactorial causal relationship.
Recently, different studies have demonstrated the presence of significant associations between extracerebral abnormal venous flow and other neurological disorders, including transient global amnesia ( 11 – 13 ) , transient blindness ( 14 ) , cough headache, exertional headache ( 15 ) , and idiopathic intracranial hypertension ( 16 ) . However, most physicians do not assign practical importance to the cerebral venous circulation, probably due to poor knowledge of the venous system, its great anatomical variability and the consequences of its malfunction. It is easy ‘to forget’ the venous system, as disturbances of arterial blood supply and cerebrospinal fluid circulation are considered more clinically relevant.
It goes without saying that it falls to the medical community to answer, in a rigorous scientific way, the questions currently posed by MS patients, but the influence of extracerebral abnormal venous flow on disease risk and evolution must be explored not only in multiple sclerosis but also in other neurological disorders
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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