1,720,969 research outputs found
Optimizing tissue pathophysiology with computed tomography perfusion imaging in acute ischemic stroke
No full textBackground: Ischemic stroke is the leading cause of adult disability in the developed world. When a blood vessel within the brain becomes occluded, there is a volume of tissue which immediately dies, the ischemic core, and a volume of tissue which is hypo-perfused and will die within hours if the occlusion is not removed, the ischemic penumbra. Salvage of the ischemic penumbra by reperfusion can be achieved with intravenous thrombolysis which activates the bodies’ anti-clotting system to dissolve a thrombus, or mechanical removal of the clot with thrombectomy. Computed tomography perfusion (CTP) is a clinically available brain imaging technique which not only assists with positively confirming the diagnosis of acute ischemic stroke, but also assists reperfusion therapy decision making in clinical practice by providing information about brain tissue viability (salvageable versus non-salvageable tissue). The volume of the ischemic core has been shown to be related to patient outcomes, and the volume of the penumbra has also been shown to relate to treatment response potential. However, the measurement of penumbra and infarct core with CTP can be varied due to different structural tissue compartments of the brain (grey matter and white matter) and different algorithms applied to post-processing of raw imaging (standard singular value deconvolution (sSVD) and standard singular value deconvolution with delay and dispersion correction(ddSVD). This thesis incorporated a series of studies, aimed to increase the precision and accuracy of the tissue pathophysiology measures in acute ischemic stroke with CTP and relate the relevant measurement of ischemic penumbra and infarct core to patient outcomes. Methods: This thesis included acute ischemic stroke patients from two data sets: (1) A previously collected data set of acute ischemic stroke patients admitted to the John Hunter Hospital within 6 hours of symptom onset, underwent baseline MRI within 1 hour of the initial CTP, and follow-up MRI at 24-hour. (2) Acute ischemic strokes patients recruited into the INternational Stroke Perfusion Imaging REgistry (INSPIRE). National Institutes of Health Stroke Scale (NIHSS) was performed at baseline and 24-hour to assess the stroke severity. A modified Rankin Score (mRS) was performed at day-90 post-stroke to evaluate patient outcomes. All perfusion imaging were post-processing with MIStar (Apollo Medical Imaging Technology, Melbourne, Australia) using sSVD and/or ddSVD as post-processing algorithms. Results: The first study in this thesis derived the optimal threshold of penumbra and infarct core for gray matter and white matter. This study demonstrated that separated tissue-specific thresholds for gray matter and white matter increased volumetric agreement with acute diffusion-weighted imaging. Gray matter had considerably higher infarct core thresholds than white matter. Furthermore, a single threshold, delay time (DT) >3seconds from ddSVD accurately defined penumbra in gray matter and white matter, as well as mixed measures of gray matter and white matter.
The following three studies in this thesis aimed to relate the relevant measurement of penumbra and infarct core to patient outcomes. This thesis demonstrated that in acute ischemic stroke patients who received alteplase, after correcting for baseline infarct core volume, for each percentage of penumbral volumes that was salvaged, the odds of a patient having an excellent clinical outcome increased by 7.4%. Furthermore, the perfusion imaging mismatch classification with DT was the optimal mismatch criteria as a patient selection tool for reperfusion therapy, in large vessel occlusion patients who receive intravenous thrombolysis only and patients who receive endovascular thrombectomy. Lastly, this thesis also found that patients with larger baseline CTP infarct core (>30mL) and “proximal” large vessel occlusion, with poorer collaterals clearly benefited from complete reperfusion after endovascular thrombectomy compared to complete reperfusion after intravenous thrombolysis alone. However, more “distal” large vessel occlusion patients with smaller baseline infarct cores and better collaterals, did not have additional benefit from complete reperfusion after endovascular thrombectomy compared with intravenous thrombolysis alone. Conclusion: The findings of this thesis supported that CTP was able to accuratly and precicely define acute ischemic tissue pathophysiology. Moreover, the accurate measures of brain tissue viability were directly related to patient clinical outcome regardless of the type of treatment received (intravenous thrombolysis or thrombectomy), and the likelihood of the success of reperfusion therapy. Importantly, the relationship between the baseline tissue pathophysiology of the ischemic core and penumbra to patient outcomes was seen to be significantly different depending on treatment type
sj-docx-1-jet-10.1177_15266028231201098 – Supplemental material for Cost-Effectiveness of Endovascular Thrombectomy in M2 Occlusion Stroke: Real-World Experience Versus Clinical Trials
No full textSupplemental material, sj-docx-1-jet-10.1177_15266028231201098 for Cost-Effectiveness of Endovascular Thrombectomy in M2 Occlusion Stroke: Real-World Experience Versus Clinical Trials by Lan Gao, Elise Tan, Chushuang Chen, Timothy Kleinig, Bernard Yan, Andrew Cheung, Chris Levi, Carlos Garcia-Esperon, Dennis Cordato, Chris Blair, Longting Lin, Mark Parsons and Andrew Bivard in Journal of Endovascular Therapy</p
sj-docx-1-wso-10.1177_17474930221138707 – Supplemental material for Poor collateral flow with severe hypoperfusion explains worse outcome in acute stroke patients with atrial fibrillation
No full textSupplemental material, sj-docx-1-wso-10.1177_17474930221138707 for Poor collateral flow with severe hypoperfusion explains worse outcome in acute stroke patients with atrial fibrillation by Jianhong Yang, Yuefei Wu, Xiang Gao, Qing Shang, Yao Xu, Qing Han, Jichuan Li, Chushuang Chen, Andrew Bivard, Mark W Parsons and Longting Lin in International Journal of Stroke</p
WSO884529 Supplemetal Material - Supplemental material for Comparing mismatch strategies for patients being considered for ischemic stroke tenecteplase trials
No full textSupplemental material, WSO884529 Supplemetal Material for Comparing mismatch strategies for patients being considered for ischemic stroke tenecteplase trials by Andrew Bivard, Xuya Huang, Christopher R Levi, Bruce CV Campbell, Bharath K Cheripelli, Chushuang Chen, Dheeraj Kalladka, Fiona C Moreton, Ian Ford, Stephen M Davis, Geoffrey A Donnan, Keith W Muir and Mark W Parsons in International Journal of Stroke</p
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
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