1,720,961 research outputs found
Midterm Follow-up Geometrical Analysis of Thoracoabdominal Aortic Aneurysms Treated with Multilayer Flow Modulator
No full textBackground: Aim of our study is the analysis of clinical results and aneurysmal sac evolution after multilayer flow modulator (MFM) placement, in patients with thoracoabdominal aortic aneurysms (TAAs). Methods: All patients with asymptomatic TAA treated at our institution between 2012 and 2014 with MFM were retrospectively analyzed. Thirty-day evaluated outcomes were mortality and complications. Follow-up evaluated outcomes were mortality, aneurysm collateral branches patency, and reintervention. A geometrical analysis of 2-year follow-up computed tomography scans was carried out to evaluate the total aneurysm volume, the percentage of aneurysm growth, and the evolution of maximum aneurysm diameter. Results: Seven patients (mean age: 71.8 years, range: 63–85 years) were considered in the study. Mean preoperative aneurysm diameter was 6.8 cm (range 6–8.3 cm). No 30-day mortality or complications were observed. Mean follow-up was 29.4 months. During follow-up, 3 deaths (42.8%) were observed, not related to MFM complications. Reintervention rate was 42.8%, occurred in all cases after 2-year follow-up; in 2 cases, the reintervention was necessary due to an excessive increase of the aneurysmal sac. During the follow-up, a mean growth rate of 6 mm/year (4 patients) for the diameter of the aneurysm external wall and a total aneurysm volume increase from 2.45 × 105 mm3 to 3.50 × 105 mm3 (4 patients) was evaluated. Conclusions: Our results have shown no mortality related to aneurysm rupture during the follow-up and high rate of reinterventions after MFM placement. Further geometrical analyses, based on the proposed approach, regarding a larger group of patients with long-term follow-up are required to draw indications about the MFM use
Assessment of geometrical remodelling of the aortic arch after hybrid treatment
No full textThe aim of this study was to measure the morphological remodelling of the ascending aorta, aortic arch and thoracic aorta after aortic arch hybrid treatment including debranching and stent graft implantation. Preoperative, 1-month and 1-year follow-up of computed tomography angiography scans of 22 patients were analysed to compute the lumen centreline from the aortic root to the coeliac trunk, and the following measurements were derived: the total centreline length, distance from the aortic root to the left subclavian artery, distance from the left subclavian artery to the distal landing zone. For both pre- and postoperative centrelines, the pointwise curvature was measured at the proximal and the distal landing zones. The meancurvature values of the whole aortic segment and the endografting region of the ascending and the descending aorta were measured. Surface outerline was computed as well, and curvature values at the endograft landing points were extracted. At the 1-month follow-up, centreline length were already significantly increased (382.66 48.69 to 388.1 50.75 mm; P = 0.01). Centreline pointwise curvature increased in the proximal (+29%, P = 0.011) and the distal zones (+63%, P = 0.004). Similarly, pointwise curvature of the outerline significantly increased in the proximal (+77%, P = 0.01) and the distal landing zones (+100%, P = 0.04). The centreline mean curvature increased in the ascending aorta (+7%, P = 0.02) and decreased in the endografting region (-3.3%, P = 0.004). No evidence of a relationship of such a remodelling with the type of endograft and the type of pathology was observed. This remodelling trend was confirmed by the analysis of 1-year computed tomography angiographies. Hybrid arch repair was associated with a significant elongation of the vessel and a significant increase in the curvature on the ascending aorta and the descending aorta and on the endograft proximal and the distal landing zones.. © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved
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
In Vitro Evaluation of Upstream and Downstream Influences on Blood Pressure of the Hybrid Treatment of Thoracoabdominal Aortic Aneurysms
No full textBACKGROUND: The aim of our study was to assess, by means of an experimental model, whether different geometries in retrograde bypass and stent-graft deployment may affect upstream and downstream blood pressure in hybrid treatment.
METHODS: An in vitro model of the arterial circulation has been prepared, which consists of a peristaltic pump, silicon tubes with geometrical and mechanical properties close to realistic arteries, a terminal reservoir kept at constant pressure, and a sequence of pressure transducers. The system allows us to study the pressure wave propagation in physiological conditions and simulate the patient's conditions as a result of debranching in 2 different configurations.
RESULTS: In configuration 1, the mean pressure value (Kpa) was 4.72 in silicone tube before stent graft and debranching, 4.59 in visceral and renal bypass, and 4.38 in silicone tube after stent graft and debranching. In configuration 2, the mean pressure value (Kpa) was 5.22 in silicone tube before stent graft and debranching, 4.48 in visceral and renal bypass, and 4.99 in silicone tube after stent graft and debranching.
CONCLUSION: The experimental data suggest that the debranching geometry and the material of the grafts and stent grafts change significantly the physiological arterial pressure possibly leading to an augmented pressure upstream of the stent grafts, owing to retrograde pressure waves toward the heart, and a decreased pressure downstream visceral and renal arteries
Early evaluation of precise deployment with the new low profile Zenith Alpha Thoracic Endoprosthesis in thoracic aortic disease
No full textBACKGROUND: Endovascular treatment of thoracic aortic disease currently allows to treat high risk patients with better results than open repair. It represents the first option for treatment according to the most recent guidelines. The aim of the study is to evaluate the early results of the low profile Zenith Alpha Thoracic Endoprosthesis (ZATE). METHODS: Between October 2012 and July 2015, 14 asymptomatic patients were treated with ZATE. 10 patients were male, mean age was 71, 7 years (range 58 - 85 years). 8 patients presented with atherosclerotic aortic aneurysm (7 thoracic aneurysm and 1 type I thoracoabdominal aneurysm), 2 chronic type B aortic dissection, 1 type IV endoleak 5 years after TEVAR, 3 aortic arch penetrating ulcer complicated by pseudoaneurysm. Hybrid staged procedures in 11 patients included 7 total aortic arch debranching (1 single (innominate) chimney stent graft + Carotid-Carotid-Subclavian), 2 carotid-carotid-subclavian artery bypass, 2 carotid- subclavian artery bypass. RESULTS: No 30-day mortality or major complications were observed. The mean length of stay was 7.3 days (range 4-14 days). Mean procedure time, X ray time and Contrast load were 115 min (range 90-150 min), 20 min (range 10-30) and 79 mL (range 40-120 mL) respectively. 25 stent grafts were implanted. The mean follow up was 21 months (range 14 - 32 months). No mortality and no major complications were observed during the follow-up. In case of arch debranching with landing 0 and 1 zone the mean distance between the beginning of the endoprosthesis and the debranching inflow vessel was 5.5 mm (±2.4 mm) CONCLUSIONS: The use of ZATE could be a viable alternative for treating patients with aortic arch proximal landing zone to facilitate the precise deployment. Larger case studies and longer follow-up are needed
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