1,720,960 research outputs found
Longitudinal analysis of atherosclerotic plaques evolution: an 18F-NaF PET/CT study
No full text18F-NaF-PET/CT can detect mineral metabolism within atherosclerotic plaques. To ascertain whether their 18F-NaF uptake purports progression, this index was compared with subsequent morphologic evolution
Correlation between thoracic aorta 18F-natrium fluoride uptake and cardiovascular risk
No full textBackground and Aims: 18F Natrium Fluoride (NaF) has been proposed as a clinical tool to identify and quantify ongoing arterial calcification. Estimation of NaF uptake by vessel walls is feasible in the majority of large vessels; it is conversely more challenging within the coronary tree, given the small size of these vessels and the artifacts from cardiac movement. In CT-based studies, thoracic artery calcification has been linked to both coronary calcification and cardiovascular risk (CVR). Moreover, among thoracic segments, descending aorta has demonstrated the greatest correlation to CVR and to CV events. In this study, we evaluated NaF uptake in different segments of the thoracic aorta, its difference among CVR groups and its correlation with the absolute CVR value.
Patients and Methods: 78 patients (44 females, mean age 63, range 44-83) underwent whole body NaF PET/CT, to detect intraosseous localization of breast or prostate cancer. CVR risk score was assessed with a modified version of the Framingham model, accounting BMI in lieu of cholesterol levels; patients were divided in three CVR categories: low (LR), medium (MR) and high risk (HR), who had a likelihood of 10-years CV events of <10%, 10-20% and >20%, respectively. NaF uptake was measured by manually drawing volumes of interest (VOI) on the ascending aorta, on the aortic arch, on the descending aorta and on the myocardium; average SUV measured within these VOI was normalized for blood-pool SUV, assessed in the inferior vena cava, to obtain target-to-background ratio (TBR). Values from the three aortic segments were then averaged to obtain an index of the whole thoracic aorta.
Results: There was a significant difference in whole thoracic aorta ??? TBR between HR and LR (1.84±0.76 vs 1.07±0.3, p<0.001), but also between MR and HR-LR (1.4±0.4, p<0.02 and p<0.01, respectively). The most efficient CVR stratification was however observed in the descending aortic segment: significance of the TBR difference between HR vs LR, HR vs MR and MR vs LR was 0.0004, 0.008 and 0.01, respectively. Correlation between TBR and CVR was appreciable when the whole thoracic aorta was considered (R=0.67), but it peaked when correlating the descending thoracic segment (R=0.75), in comparison with the aortic arch and the ascending segment (R=0.55 and 0.53, respectively).
Conclusions: Fluoride uptake within the thoracic aorta wall effectively depicts patients' risk class and closely correlates with cardiovascular risk. Among segments, descending thoracic aorta is the most effective in CVR determination
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
18F-NaF uptake by atherosclerotic plaque on PET/CT imaging: Inverse correlation between calcification density and mineral metabolic activity
No full textSeveral studies have highlighted the role of vascular (18)F-NaF uptake as a marker of ongoing calcium deposition. However, accumulation of (18)F-NaF is often inconsistent with localization of arterial plaque. Calcification activity and thus (18)F-NaF uptake might prevail in the earlier plaque stages. To test this hypothesis, we evaluated (18)F-NaF uptake in plaque of 3 different densities, using density as a marker of calcification progression. We also tested whether attenuation-weighted image reconstruction affects (18)F-NaF uptake in the different plaque stages.
METHODS:
Sixty-four oncologic patients (14 men and 50 women; mean age, 65.3 ± 8.2 y; range, 26-81 y) underwent (18)F-NaF PET/CT. A volume of interest was drawn on each plaque within the infrarenal aorta to assess mean standardized uptake value and attenuation (in Hounsfield units [HU]). Plaque was then categorized as light (<210 HU), medium (211-510 HU), or heavy (>510 HU). Standardized uptake value was normalized for blood (18)F-NaF activity to obtain the plaque target-to-background ratio (TBR). During this process, several focal, noncalcified areas of (18)F-NaF were identified (hot spots). The TBR of the hot spots was computed after isocontour thresholding. The TBR of a noncalcified control region was also calculated. In 35 patients, the TBR of non-attenuation-corrected images was calculated.
RESULTS:
The average TBR was highest in light plaque (2.21 ± 0.88), significantly lower in medium plaque (1.59 ± 0.63, P < 0.001), and lower still in heavy plaque (1.14 ± 0.37, P < 0.0001 with respect to both light and medium plaque). The TBR of the control region was not significantly different from that of heavy plaque but was significantly lower than that of light and medium plaque (P < 0.01). Hot spots had the highest absolute TBR (3.89 ± 1.87, P < 0.0001 vs. light plaque). TBRs originating from non-attenuation-corrected images did not significantly differ from those originating from attenuation-corrected images.
CONCLUSION:
Our results support the concept that (18)F-NaF is a feasible option in imaging molecular calcium deposition in the early stages of plaque formation, when active uptake mechanisms are the main determinants of calcium presence, but that retention of (18)F-NaF progressively decreases with increasing calcium deposition in the arterial wall. Our data suggest that non-attenuation-corrected reconstruction does not significantly affect evaluation of plaque of any thickness
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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