1,720,960 research outputs found
Central hemodynamic estimates by ultrasound-derived carotid distension waveforms: comparison with applanation tonometry
No full textCOMPARISON OF TWO RADIO-FREQUENCY BASED ULTRASOUND SYSTEMS FOR ASSESSMENT OF CAROTID STIFFNESS
No full textObjective: Measurement of arterial stiffness is becoming widely used for assessing cardiovascular risk and target organ damage. Two commercially available ultrasound systems (QAS, Esaote, Italy and eTracking, Aloka, Japan) provide radio-frequency (RF)-based tracking of carotid wall, thus allowing automatic accurate real-time determination of vessel diameter and distension, and subsequent calculation of indices of carotid stiffness. The measurement is performed in a single line by eTracking and in 16 equidistant lines within the region of interest by QAS. Aim of the present study was to evaluate whether the measures of carotid stiffness obtained by the two systems are interchangeable, and to assess the intra- and inter-operator variability of acquisitions. Design and methods: In the same session, MyLab 70 (Esaote, Italy) and Alpha 7 (Aloka, Japan) were used in random order to measure (2 cm before the flow divider) right common carotid artery (CCA) diameter and distension, and to calculate beta-index (Beta) in 104 subjects divided into 4 groups: 24 healthy controls (NL, age 32±7 yy), 24 prehypertensive subjects (PHBP, age 50±10 yy), 26 hypertensive patients (HBP, age 57±10 yy) and 27 type 2 diabetic patients (DM, age 62±6 yy). In 30 subjects, the second acquisition was performed after a 60-minute interval, both by the same operator and by a second operator. The reported values represent a mean of 3 measurements. Results: Brachial BP was similar during the acquisition with QAS and eTracking (p0.94), and the correlation between the two systems for CCA distension and Beta was high (r0.94 and 0.90, respectively,......
Local carotid stifness versus carotid-femoral pulse wave velocity in normal subjects and patients with risk factors
No full textComputer Assisted Methods in Peripheral vascular Ultrasound: CAMPUS
No full textPurpose Advanced peripheral vascular ultrasound techniques, when combining high temporal and spatial resolution, infonnation intrinsic to the radiofrequency (RF) raw data, and simultaneous acquisition of physiological signals, have a potential to expand the range of clinical applications well beyond the currently used 2D and duplex/triplex imaging. Combining on-line computerized image and signals acquisitions and processing together with off-line capabilities of advanced analyses, allows to obtain detailed infonnation on vascular physiology and disease. This paper presents a short overview on some recent clinical applications and perspectives deriving from computer assisted methods applied to RF-based ultrasound. Estimate and characterization of atherosclerotic vascular disease from preclinical to advanced states, as well as novel approaches to noninvasive hemodynamics, will be briefly outlined. Methods RF-based automatic measurements are implemented in commercially available US systems for accurate estimate of common carotid intimamedia thickness (CCA-IMT), an established marker of preclinical vascular disease and predictor of risk in selected populations. It is potentially useful for improving risk stratification respect to estimates based upon conventional risk factors, which account per se about 50% only of the probability to develop a cardiovascular disease. Online arterial continuous tracking of arterial wall distension curves calibrated for blood pressure, together with contour wave analysis, yields not only indices of local arterial stiffness but also data on arterial wave reflection and LV ejection function
An average daily physical activity is an independent determinant of local carotid stiffness and myocardial performance
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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
Radiofrequency-based carotid wall tracking: a comparison between two different systems.
No full textObjectives: A direct measurement of carotid stiffness implies an accurate assessment of changes in carotid diameter and pressure during cardiac cycle. Radiofrequency-based wall-tracking systems (WTS) are capable to track arterial wall movement with adequate spatial and temporal resolution, and to provide carotid pressure estimate from calibrated distension waveforms. The aim of the present study was to compare the values of carotid distension and beta-stiffness index acquired in the same population by two commercially available WTS, in order to determine whether their measures can be pooled in clinical studies. In addition, a local carotid pulse pressure (PP) obtained from calibrated distension waveforms was compared with that obtained from pressure waveforms. Methods: In 105 patients, right common carotid artery (CCA) systo-diastolic excursions were assessed during the same session and by the same operator both by WTS implemented in Esaote system (QAS, MyLab) and in Aloka system (E-track; Alpha 10). In 78 patients, carotid PP was also estimated by applanation tonometry. Results: Despite comparable blood pressure and heart rate values during the two acquisitions, CCA distension was significantly lower (363±162 vs. 458±176μm, P<0.0001) and beta-stiffness index (11.9±5.5 vs. 9.4±3.8, P<0.0001) higher with Esaote as compared to Aloka. PP obtained from calibrated pressure and distension waveforms was comparable (42.6±11.4 vs. 43.0±10.7mmHg, P=0.51). Conclusions: The values of carotid distension and stiffness obtained by two different WTS are not interchangeable and cannot be merged into a common database. Calibrated distension curves may provide an acceptable estimate of local carotid pressure
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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