1,721,048 research outputs found
Two birds with one stone: integrated assessment of coronary physiology and plaque vulnerability from a single angiographic view—a case report
No full textBackground Physiology-guided coronary revascularization was shown to improve clinical outcomes in multiple patient subsets, whilst in those presenting with acute coronary syndromes, it seems to be associated with an excess of cardiovascular events. One of the major drawbacks in this setting is the potential deferral of non-flow-limiting but 'vulnerable' coronary plaques. Case summary A 40-year-old patient presented with a myocardial infarction without ST-segment elevation (NSTEMI). At the invasive coronary angiography (ICA) a sub-occlusive stenosis on his left circumflex artery was detected and treated with percutaneous coronary intervention (PCI). The treatment of a concomitant intermediate eccentric focal stenosis on the right coronary artery (RCA) was deferred after a negative pressure wire-based physiological assessment. The patient was re-admitted 9 months later due to a recurrent NSTEMI, and a severe progression of the deferred RCA lesion was found at the ICA. In retrospect, an angiography-based assessment of physiological severity and plaque vulnerability of the non-culprit RCA stenosis by means of Murray's law-based QFR (& mu;QFR) and radial wall strain (RWS) was performed. At baseline, & mu;QFR value (0.90) corroborated the non-ischaemic findings of wire-based assessment. However, RWS analysis showed a marked hotspot (maximum RWS value 27.7%), indicating the presence of a vulnerable plaque. Discussion Radial wall strain is a novel biomechanical deformation index derived from coronary angiography. Segments with high RWS are associated with lipid-rich plaques that are prone to progression and plaque rupture. Therefore, the identification of RWS hotspots might potentially improve the risk stratification of non-culprit lesions and empower secondary prevention strategies
Novel computational biomechanics for the assessment of coronary plaque vulnerability and its clinical implications
No full textAcute coronary syndromes (ACS) continue to be one of the major causes of mortality around the world. Accumulating evidence indicates that thrombosis plays a critical role in the pathogenesis of ACS. Autopsy studies have revealed that plaque rupture remained the main cause of fatal coronary thrombosis, highlighting the need for early detection of plaques that are prone to rupture. Coronary biomechanical assessment provides a promising tool for the detection of vulnerable plaque, as plaque rupture is ultimately a mechanical process that can be accurately modelled, simulated and predicted from the interplay between flow, pressures and plaque composition within the coronary wall. The objective of this thesis is to develop novel methods for the biomechanical assessment of coronary plaque vulnerability. Finite element analysis (FEA) provides a valuable solution for the assessment of biomechanical environment within the vessel wall. One of the prerequisites for precise FEA results is the availability of an accurate geometric model. A fully automated deep learning (DL)-based plaque characterization algorithm was recently developed for optical coherence tomography (OCT) images, showing the potential for providing detailed geometric models for biomechanical assessment. Chapter 2 of this thesis validated the reliability of this DL algorithm in detecting calcified plaque, the component which plays an essential role for determining biomechanical environment within the vessel wall. The validation for OCT-DL was achieved using comprehensive tissue characterization technologies including OCT-derived optical properties, intravascular ultrasound (IVUS)-VH and echogenicity on accurately aligned in-vivo imaging of human coronary arteries. The concordance between OCT-DL and other modalities was assessed by kappa statistics. As a result, forty-three calcified plaques were detected by DL in 72 matched anatomic slices, 41 (95%) were confirmed by optical properties. Weighted kappa between OCT-DL and GS-IVUS, IVUS-VH and echogenicity were 0.69, 0.60 and 0.60, respectively. After having excluded artefactual optical shadowing (n=5) generated by guidewire or platinum marker, kappa increased to 0.77, 0.68 and 0.69, with agreement ranging between 90% and 93%. OCT empowered by DL showed substantial agreement with optical and ultrasound signals, revealing the reliability of using DL-aided OCT to assess the biomechanical environment within the vessel wall. At the same time, accurate delineation of coronary artery outer boundary, specifically the vessel contour, ensures the reliable reconstruction of the arterial geometric model, which in turn allows for a precise assessment of coronary biomechanics. The good penetration of ultrasound signals through blood and soft tissue makes IVUS the standard modality for precise vessel contour delineation and plaque burden (PB) assessment. In contrast, the near-infrared light used for OCT limits its penetration depth to only 1.5–2.0 mm, potentially hindering the accurate vessel contour delineation using OCT, despite its high image resolution. OCT-DL incorporates the information from adjacent OCT crosssectional images and the prior knowledge of regular shape of vessel contour (either circular or elliptical). As a result, OCT-DL is able to extrapolate the vessel contour and to provide an estimation of the PB from OCT images. This advancement offers a more efficient and automated solution for reconstructing the artery geometric model. Chapter 3 of this thesis validated the performance of OCT-DL in vessel contour delineation and PB assessment using precisely co-localized IVUS images. OCT cross-sections were further divided into four subgroups with different media visibility level to investigate the impact of media visibility on numerical differences between OCT-derived and IVUS-derived PB. As a result, 64 paired OCT and IVUS cross-sections were compared. OCT-DL showed good concordance with IVUS for PB assessment (ICC=0.81, difference=-3.53 ± 6.17%, p65%. This study proved the capability of OCT-DL in accurately estimating PB and delineating vessel contours, regardless of media visibility. Based on the precise geometric model reconstructed using OCT-DL, Chapter 4 of this thesis proposed a novel approach to derive the changes in plaque structural stress (ΔPSS) during the cardiac cycle in-vivo using a combination of OCT images and intracoronary pressure recordings. The study enrolled all the intermediate lesions from a previous OCT study. OCT cross-sections at representative positions within each lesion were selected for ΔPSS analysis. As a result, a total of 50 lesions from 41 vessels were analysed. A significant ΔPSS gradient was observed across the plaque, being maximal at the proximal shoulder (45.7 [32.3, 78.6] kPa), intermediate at minimal lumen area (MLA) (39.0 [30.8, 69.1] kPa) and minimal at the distal shoulder (35.1 [28.2, 72.3] kPa; p=0.046). The presence of lipidic plaques was observed in 82% of the diseased segments. Lipidic plaque area showed good correlation with relative lumen deformation (r=0.88, p<0.001). Larger relative lumen deformation and ΔPSS were observed in diseased segments, compared with normal segments (percent diameter change: 8.2 ± 4.2% versus 6.3 ± 2.3%, p=0.04; ΔPSS: 59.3 ± 48.2 kPa versus 27.5 ± 8.2 kPa, p<0.001). ΔPSS was positively correlated with plaque burden (r=0.37, p<0.001) and negatively correlated with fibrous cap thickness (r=-0.25, p=0.004). ΔPSS has been proven to be able to provide a feasible method for assessing plaque biomechanics in-vivo from OCT images, consistent with previous biomechanical and clinical studies based on different methodologies. Larger ΔPSS at proximal shoulder and MLA indicates the critical sites for future biomechanical assessment. Despite the precise biomechanical assessment from high-resolution OCT images, the penetration rate of intracoronary imaging during diagnostic coronary angiography is relatively low, particularly in underdeveloped regions. The development of a simplified and cost-effective alternative for biomechanical assessment remains an outstanding goal in the field. As the corner stone for the diagnosis and management of coronary artery disease, dynamic angiogram records directly how vessel moves and deforms over the entire cardiac cycle based on the imprint left on the lumen contour. Aided by artificial intelligence, a novel method has been proposed enabling real-time assessment of radial wall strain (RWS), which is computed as the relative luminal deformation throughout cardiac cycle, from coronary angiography (RWSAngio). Chapter 5 in this thesis validated the agreement between novel RWSAngio and RWS derived from OCT, using the methodology proposed in Chapter 4 as the established reference standard (RWSOCT). The study enrolled all lesions from a previous OCT study and OCT was automatically coregistered with angiography. RWSOCT was analysed using FEA on OCT cross-sections at 1- mm interval. The luminal deformation in the direction of minimal lumen diameter was used to derive RWSOCT, following same definition as RWSAngio. The maximal RWSOCT and RWSAngio at normal segments adjacent to interrogated lesion were also analysed. As a result, RWSOCT analysis was performed in 578 OCT cross-sections from 45 lesions stemming from 36 patients. RWSAngio showed good correlation and agreement with RWSOCT (r=0.91, p<0.001; Lin’s coefficient=0.85). RWSAngio in atherosclerotic segments was significantly higher than normal segments (12.6% [11.0, 16.0] versus 4.5% [2.9, 5.5], p<0.001). The intraclass correlation coefficient for intra- and inter-observer variability in repeated RWSAngio analysis were 0.92 (95% CI:0.87-0.95) and 0.88 (95% CI:0.81-0.92), respectively. The mean analysis time of RWSOCT and RWSAngio for each lesion was 95.0 ± 41.1 and 0.9 ± 0.1 minutes, respectively. This study demonstrated the reliability of biomechanical assessment solely from angiography. In conclusion, this thesis conducted comprehensive validation of the performance of OCT-DL algorithms, including the automated detection of calcified plaques, delineation of vessel contour and evaluation of plaque burden. These validations led to the development of a novel approach that utilizes the geometric model reconstructed from OCT-DL results for precise OCT-based biomechanical assessment. Additionally, this thesis proposed a simplified method that enables real-time biomechanical assessment solely from coronary angiography and validated this method against the FEA results from co-registered OCT. The excellent concordance that we have observed demonstrates great potential for using the routinely available coronary angiography as a cost-effective tool in order to assess biomechanical properties of diseased coronary arteries in large populations
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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