1,721,021 research outputs found
Prediction of Amyloid Positivity in Lewy Body Disease Using Early-Phase 18F-FP-CIT PET Images
No full textPurpose: To explore whether alterations in regional cerebral perfusion observed on early-phase F-18-FP-CIT PET imaging could predict beta-amyloid positivity in patients with Lewy body disease (LBD). Methods: We enrolled 132 patients with LBD (78 dementia with Lewy bodies and 54 Parkinson disease) who underwent dual-phase F-18-FP-CIT PET and 18F-FBB PET scans at initial assessment. Patients were divided into the amyloid-positive (n=69) and amyloid-negative (n=63) groups. We compared regional uptake on early-phase F-18-FP-CIT PET images between the 2 groups, whereas a linear discriminant analysis (LDA) was performed to predict beta-amyloid positivity based on the standard uptake value ratios (SUVRs) of each region of interest. Mediation analyses were performed to evaluate whether regional cerebral perfusion mediated the association between beta-amyloid load and longitudinal changes in the Mini-Mental State Examination (MMSE) scores. Results: There were no significant differences in age, sex, educational attainment, MMSE scores, motor deficits, or striatal dopamine depletion between the amyloid-positive and amyloid-negative groups. The amyloid-positive group exhibited decreased uptake in the parietal, precuneus, middle/inferior temporal, and isthmus cingulate cortices, as well as increased uptake in the caudate, compared with the amyloid-negative group on early-phase F-18-FP-CIT PET images. LDA prediction model demonstrated that SUVRs of the inferior parietal cortex and caudate optimally distinguished the 2 groups. Greater beta-amyloid burden was associated with a more rapid decline in MMSE scores, which was partially mediated by inferior parietal hypoperfusion. Conclusions: Alterations in regional cerebral perfusion on early-phase F-18-FP-CIT PET imaging may serve as a useful biomarker for predicting beta-amyloid deposition in LBD.
Hypoperfusion in Alzheimer's Disease-Prone Regions and Dementia Conversion in Parkinson's Disease
No full textPurpose of the ReportAlthough early detection of individuals at risk of dementia conversion is important in patients with Parkinson's disease (PD), there is still no consensus on neuroimaging biomarkers for predicting future cognitive decline. We aimed to investigate whether cerebral perfusion patterns on early-phase 18F-N-(3-fluoropropyl)-2 beta-carboxymethoxy-3 beta-(4-iodophenyl) nortropane (18F-FP-CIT) PET have the potential to serve as a neuroimaging predictor for early dementia conversion in patients with PD. Materials and MethodsIn this retrospective analysis, we enrolled 187 patients with newly diagnosed PD who underwent dual-phase 18F-FP-CIT PET at initial assessment and serial cognitive assessments during the follow-up period (>5 years). Patients with PD were classified into 2 groups: the PD with dementia (PDD)-high-risk (PDD-H; n = 47) and the PDD-low-risk (PDD-L; n = 140) groups according to dementia conversion within 5 years of PD diagnosis. We explored between-group differences in the regional uptake in the early-phase 18F-FP-CIT PET images. We additionally performed a linear discriminant analysis to develop a prediction model for early PDD conversion. ResultsThe PDD-H group exhibited hypoperfusion in Alzheimer's disease (AD)-prone regions (inferomedial temporal and posterior cingulate cortices, and insula) compared with the PDD-L group. A prediction model using regional uptake in the right entorhinal cortex, left amygdala, and left isthmus cingulate cortex could optimally distinguish the PDD-H group from the PDD-L group. ConclusionsRegional hypoperfusion in the AD-prone regions on early-phase 18F-FP-CIT PET can be a useful biomarker for predicting early dementia conversion in patients with PD.
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
Association of Striatal Dopaminergic Depletion and Cerebral Perfusion With Cognition in Brain-First and Body-First Parkinson's Disease
No full textPurpose:We aimed to investigate whether the patterns of striatal subregional dopamine loss and cerebral perfusion alterations differed between the 2 types of Parkinson's disease (PD) (ie, brain-first and body-first PD) and had an impact on cognitive prognosis in PD.Patients and Methods:This retrospective study reviewed the data of newly diagnosed patients with PD who underwent dual-phase dopamine transporter (DAT) scans in tertiary medical centers. We classified the patients into 2 groups based on the rapid eye movement sleep behavior disorder (RBD) screening questionnaire: PD with RBD (body-first PD) and PD without RBD (brain-first PD) groups. Then, we investigated intergroup differences in subregional DAT availability, regional cerebral perfusion, and the rates of dementia conversion.Results:After adjusting for confounding variables, the body-first group exhibited lower DAT availability in the anterior putamen than the brain-first group (beta=-0.10, SE=0.04, P=0.044). In comparative analyses of regional cerebral perfusion, the body-first group exhibited lower regional perfusion in the bilateral parieto-occipital area and left cerebellum than the brain-first group, and vice versa in the brainstem, left hippocampus, right pallidum, bilateral thalamus, and ventral diencephalon. The dementia conversion rate was significantly higher in the body-first group (HR=1.78, P=0.027) than in the brain-first group, which was largely mediated by DAT availability in the anterior putamen and parieto-occipital cerebral perfusion in mediation analyses.Conclusions:This study demonstrated that the patterns of striatal subregional dopamine depletion and regional cerebral perfusion differed between the brain-first and body-first PD subtypes, and these differences largely mediated inter-subtype differences in cognitive outcome.
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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