1,721,076 research outputs found
Semi-Automated analysis of coronary flow doppler images: validation with manual tracings
No full textCoronary flow velocity reserve (CFVR) is conventionally obtained by manual tracings of Doppler profiles, as ratio of stress vs baseline diastolic peak velocity. When <1.9, this parameter evidences reduced coronary flow and possible microcirculatory disease. Our goals were: 1) to develop a novel technique for semi-automated detection of Doppler flow velocity profile, allowing the automated computation of CFVR and other parameters; 2) to validate this technique in comparison with conventional measurements obtained by manual tracing; 3) to test for differences between normal (N) subjects and patients with rheumatoid arthritis (RA). Linear correlation and Bland-Altman analyses showed that the proposed method was highly accurate and repeatable compared to the manual measurements. Comparison between N and RA groups evidenced significant differences in some of the automated parameters
Feasibility of quantitative analysis of regional left ventricular function in the post-infarct mouse by magnetic resonance imaging with retrospective gating
No full textThe acute myocardial infarction(AMI) is the most frequent cause of death in the population of western countries. AMI has been mimicked in a variety of animal models and the murine model of AMI has been extensively studied as a means of clarifying changes associated with ischemic heart disease, and testing the effectiveness of new therapies[1].
The aim of this study was to test the feasibility of using cine MRI acquired with retrospective gating to quantify global and regional left ventricle function in mice with AMI.
AMI was induced in mice(n=30) by left anterior descendent coronary ligation; 10 sham mice constituted the control group. All the mice were imaged 9 days after the surgery. Cine images were obtained using a 4.7T scanner(Bruker AvanceII) with retrospective gating(IntraGate). Whole left ventricle(LV) was acquired in contiguous short axial slices and in each image LV endocardium was detected and divided into 6 sectors. For each sector, regional fractional area change(RFAC) and LV thickness were computed and used as indices of regional wall motion and function[2]. To allow the easy visualization of the results of regional LV wall motion and wall thickness of the entire ventricle in a single image, the RFAC and LV thickness were displayed in a bull’s eye format(Figure 1). Global LV end-diastolic volume, end-systolic volume and stroke volume, the ejection fraction and LV mass were also calculated (Table 1). The LV was larger in the myocardial infarcted mice, which showed a decreased ejection fraction, peak filling and peak ejection rates, and increased mass. RFAC and LV thickness progressively decreased from base to apex in the infarcted mice, being least in the anterior and antero-septal sectors, in line with the occlusion.
In conclusion, cine MRI with retrospective gating reduces acquisition times and trigger-related problems in studies of AMI. Regional LV function analysis by bull’s eye is a feasible and immediate methods allowing the localization of the effects of the induced infarction and may therefore be used in pre- and post-treatment studies.
Figure 1: Bull’s eye representations of mean RFAC (left) and mean LV wall thickness (right) in the control and AMI mice. The slices from the LV apex to base are shown from the inner to the outer circle. The red and the green tones indicate lower and higher values, respectively: the corresponding scales are shown as colour bars beside the panels.
Table 1: Global LV parameters in control and AMI group (EDV: end-diastolic volume; ESV: end-systolic volume; SV: stroke volume; EF: ejection fraction). *: p<.05 (unpaired t-test).
Control AMI
EDV (μl) 36±4 92±25*
ESV (μl)
SV (μl)
EF (μl)
LV mass (mg) 10±3
26±3
72±7
77±8 66±27*
26±4
31±10*
96±23*
References
[1] L. Monassier, A. Constantinesco, Standards of mouse model phenotyping. Edited by De Agelis MH, Chambon P, Brown S. Wiley VCH, Weinheim, 2006.
[2] E.G. Caiani, E. Toledo, P. MacEneaney, D. Bardo, S. Cerutti, R.M. Lang, V. Mor-Avi Automated interpretation of regional left ventricular wall motion from cardiac magnetic resonance imaging. Journal of Cardiovascular Magnetic Resonance, 8, 427-433, 200
Development of a method for left ventricular shape evaluation based on surfaces obtained by real-time 3D echocardiographic images
Full text linkLeft ventricular (LV) shape is strictly related to LV function. Previously proposed shape indexes suffer from their intrinsic 2D nature. Our aim was to develop a method to quantify directly 3D LV shape from LV surfaces semi-automatically detected from real-time 3D echocardiographic (RT3DE) images. First, a monodimensional shape descriptor has been obtained by sampling through an helical pattern the extracted endocardial surfaces. Then, four shape indexes have been defined by comparing the LV with reference shapes. The developed method was applied to RT3DE datasets obtained from 12 normal subjects, 8 patients with dilated cardiomiopathy and 7 ischemic patients. Some of the proposed shape indexes were able to follow chamber deformation throughout the cardiac cycle and to discriminate between normal and pathologic conditions
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
Autonomic response evaluation during gradual body weight support: comparison between spectral and symbolic analysis.
Full text linkThe robot-driven walking therapies with body weight support (BWS) are recently gaining appreciation as they can improve gait recovery in stroke survivors. However, BWS could evoke a response of the autonomic nervous system (ANS) that could be dangerous in patients with cardiovascular regulation deficit. The aim of this study is to evaluate the ANS response during BWS phases through spectral and symbolic analyses of short-term heart rate variability. This evaluation could help to tailor robot-driven walking strategies preventing discomfort and improving rehabilitation. A group of 10 normal subjects was studied during several BWS phases. Results from spectral and symbolic analyses indicated a gradual sympathetic activation together with a parasympathetic inhibition with increasing percentages of BWS. However, since changes appear mainly as trends, our findings suggest that the progressive increase of the BWS generates a light sympathetic stimulation
From Kepler’s conjecture and fcc lattice to modelling of crowding in living matter
Full text linkUp to now, sphere packing has been investigated without any reference to living matter. This study focuses on the void space (VS) of sphere packing to mimic the extracellular spaces of living tissues. It was inspired by the importance of the extracellular matrix, the vehicle of micro and macromolecules involved in cell metabolism, intercellular communication and drug delivery.
The analysis of sphere packing evidenced that in uniform random packing VS is about 1.9 times greater than in the face centered cubic (fcc) lattice (thus being very close to the 1.9 volume ratio of the cube to the sphere). This datum is a good reference for cell packing in vivo.
The disproportionate increase of VS per sphere in loose packing in vitro is analyzed having in mind the variability in volume and composition of the interstitial spaces in vivo and cell trafficking.
Arrangements of lymphocytes mimicking a two-dimensional hexagonal pattern and
dense packing of disks generated by numerical procedures, are described in 7 μm-thick haematoxylin and eosin-stained histological slices from a human lymph node. In narrow tubes simulating roundish cells arranged in limited compartments of the interstice, sphere packing is characterized by noticeable increases of VS. The VS of this packing in vitro is compatible with variability in volume and composition of the interstitial spaces and with cell trafficking in vivo. This
paper stresses that in mammalian tissues and organs cells can be packed quite more densely than spheres in the fcc lattice. As to pathology, attention is focused: (i) on overcrowding of cell
organelles in some diseases, (ii) on shrinking or swelling of high amplitude, whose opposite effects are to concentrate or dilute intracellular structures and crowding of macromolecules, and (iii) on neoplastic tissues
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
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