1,721,020 research outputs found
Multimodal MRI in the characterization of glial neoplasms: the combined role of single-voxel MR spectroscopy, diffusion imaging and echo-planar perfusion imaging
No full textINTRODUCTION: Diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI) and MR spectroscopy (MRS) provide useful data for tumor evaluation. To assess the contribution of these multimodal techniques in grading glial neoplasms, we compared the value of DWI, PWI and MRS in the evaluation of histologically proven high- and low-grade gliomas in a population of 105 patients. METHODS: Independently for each modality, the following variables were used to compare the tumors: minimum apparent diffusion coefficient (ADC) and maximum relative cerebral blood volume (rCBV) normalized values between tumor and healthy tissue, maximum Cho/Cr ratio and minimum NAA/Cr ratio in tumor, and scored lactate and lipid values in tumor. The Mann-Whitney and Wilcoxon tests were employed to compare DWI, PWI and MRS between tumor types. Logistic regression analysis was used to determine which parameters best increased the diagnostic accuracy in terms of sensitivity, specificity, and positive and negative predictive values. ROC curves were determined for parameters with high sensitivity and specificity to identify threshold values to separate high- from low-grade lesions. RESULTS: Statistically significant differences were found for rCBV tumor/normal tissue ratio, and NAA/Cr ratio in tumor and Cho/Cr ratio in tumor between low- and high-grade tumors. The best performing single parameter for group classification was the normalized rCBV value; including all parameters, statistical significance was reached by rCBV tumor/normal tissue ratio, NAA/Cr tumor ratio and lactate. From the ROC curves, a high probability for a neoplasm to be a high-grade lesion was associated with a rCBV tumor/normal tissue ratio of >1.16 and NAA/Cr tumor ratio of <0.44. CONCLUSION: Combining PWI and MRS with conventional MR imaging increases the accuracy of the attribution of malignancy to glial neoplasms. The best performing parameter was found to be the perfusion level
Goldenhar syndrome associated with contralateral agenesis of the internal carotid artery.
No full textCongenital absence of the internal carotid artery (ICA) is an extremely rare vascular anomaly. Aplasia and displacement of the horizontal portion of the petrous carotid artery have been described in a patient with mandibulofacial dysostosis. To the best of our knowledge, the association between Goldenhar syndrome and ipsilateral ICA agenesis has emerged only in one case documented in the medical literature to date. We describe here a case that illustrates the association of Goldenhar syndrome with contralateral agenesis of the ICA incidentally detected on brain magnetic resonance imaging and subsequently confirmed on magnetic resonance angiography and high resolution computed tomography
The CT appearance of two-level fractures of the posterior vertebral apophysis. A case report
No full textBilateral cerebellopontine angle lipomas.
No full textCerebellopontine angle (CPA) lipomas are extremely rare lesions and usually unilateral. We describe a case of a 36-year-old man with bilateral aural fullness that was discovered to have bilateral CPA lipomas associated with an abnormal hindbrain segmentation appearance. The patient was evaluated with 3.0T magnetic resonance imaging (MRI) system. MRI demonstrated the presence of bilateral CPA masses partially extending into the internal auditory canals. These lesions were hyperintense on both T1- and T2 weighted images. Facial and vestibulo-cochlear nerves together with tortuous vascular structures and fibro-connective septa were identified on T2-weighted 3D Fast Imaging Employing Steady-state Acquisition (FIESTA) sequences as areas of lower intensity coursing through the masses. Gadolinium administration yielded no enhancement. Conservative management was adopte
Valutazione delle correnti indotte nel cuore da intensi campi magnetici statici.
No full textTramite misure di campo magnetico statico in ambiente NMR e l'applicazione di un modello anatomico semplificato del muscolo cardiaco sono state valutate le correnti prodotte a livello di nodo senoatriale (NSA) e nodo atrioventricolare (NAV) in pazienti sottoposti a MRI clinica. Tali correnti, prodotte dal movimento del sangue nelle camere cardiache e nei vasi afferenti, se troppo elevate potrebbero avere effetti negativi sul funzionamento del cuore dal punto di vista della conduzione elettrica. La valutazioni per esposizione ad un campo magnetico statico di 3 T hanno messo in evidenza una densità di corrente indotta a NSA e NAV superiore fino a 7 volte ai valori fisiologici
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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