1,720,964 research outputs found
Validating chest MRI to detect and monitor cystic fibrosis lung disease in a pediatric cohort
No full textBackground: Computed Tomography (CT) is the gold standard to assess bronchiectasis and trapped air in cystic fibrosis (CF) lung disease, but has the disadvantage of radiation exposure. Magnetic Resonance Imaging (MRI) is a radiation free alternative.
Objective: To validate MRI as outcome measure by: correlating MRI scores for bronchiectasis and trapped air with clinical parameters, and by comparing those MRI scores with CT scores.
Methods: In patients with CF (aged 5.6-17.4 years), MRI and CT were alternated annually during routine annual check-ups between July 2007 and January 2010. Twenty-three children had an MRI performed 1 year prior to CT, 34 children had a CT 1 year prior to MRI. Bronchiectasis and trapped air were scored using the CF-MRI and CF-CT scoring system. CF-MRI scores were correlated with clinical parameters: FEV1 , Pseudomonas aeruginosa, pulmonary exacerbations and patient-reported respiratory symptoms measured on the Cystic Fibrosis Questionnaire-Revised (CFQ-R), using Spearman's correlation coefficient. MRI and CT scores were compared using intra-class correlation coefficients (ICC) and Bland-Altman plots.
Results: Fifty-seven patients who had an MRI, CT and CFQ-R during the study period were included. CF-MRI bronchiectasis correlated with FEV1 , Pseudomonas aeruginosa, pulmonary exacerbations and patient-reported respiratory symptoms. CF-MRI trapped air only correlated with FEV1 and Pseudomonas aeruginosa. ICCs between MRI and CT bronchiectasis and trapped air were 0.41 and 0.35 respectively. MRI tended to overestimate bronchiectasis compared to CT.
Conclusion: The associations between CF-MRI scores and several important clinical parameters further contributes to the validation of MRI. MRI provides different information than CT
Impact of bronchiectasis and trapped air on quality of life in cystic fibrosis lung disease - a ct and mri comparison
No full textLung morphology assessment using MRI: a robust ultra-short TR/TE 2D steady state free precession sequence used in cystic fibrosis patients
No full textTo evaluate feasibility and diagnostic quality of ultra-short TR/TE two-dimensional (2D) steady state free precession (SSFP) MRI for cystic fibrosis (CF) patients. We performed lung MRI at 1.5 Tesla in 20 CF-patients (6-17 years, 12 males). Axial, coronal, and sagittal sections were acquired in inspiration and expiration with maximum breath-hold time 10 s. MR and CT images were scored using a modified Brody scoring system to assess bronchiectasis, mucous plugging, atelectasis/consolidations, and air trapping. All images were scored by two experienced observers. A complete MR investigation took maximally 15 min. Maximal breath-holds were only 10 s and well tolerated. MRI identified major bronchiectasis, mucous plugging and atelectasis. End-expiratory scans showed patches of parenchyma with reduced signal intensity that may corresponded to areas of trapped air on expiratory CT scans. This MRI protocol based on ultra-short TR/TE 2D SSFP is quick and well tolerated and provides highly relevant imaging features as seen on CT in CF patients. Most importantly, the SNR of the expiratory scans enables to visualize air trapping. The preliminary results of this study suggest MRI as a noteworthy additional imaging tool for routine monitoring of CF patients
COMPARISON OF PROTON-MRI(MRI) AND CONTRAST ENHANCED MRI(CEMRI) IN CYSTIC FIBROSIS(CF) LUNG ASSESSMENT: SHOULD WE INCLUDE PERFUSION STUDY ROUTINELY?
No full textComparison of Chest-MRI to Chest-CT to Monitor Cystic Fibrosis (CF) Lung Disease
No full textPURPOSE: The most important components of CF lung disease are bronchiectasis (BE) and trapped air (TA). Chest-CT is the current gold standard to diagnose and
monitor BE and TA. Chest-MRI has been suggested as a radiation free alternative for CT but its spatial resolution is inferior to CT. The purpose of our study was to
do a head to head comparison to assess the sensitivity of chest-CT and chest-MRI to monitor BE and TA air in CF.
METHOD AND MATERIALS: This 2 center study was approved by the institutional review boards. 39 stable CF patients (20 female; mean age 16.7 years) had a
chest-CT and -MRI performed on the same day. MRI (Siemens Avanto): BLADE proton density (PD) transversal (TR/TE/alpha: ∞/28 ms/180o), perfusion-weighted
MRI (PWI) and Diffusion-weighted imaging (DWI). CT (Siemens Somatom): low dose; volumetric; end inspiration and end expiration: 120 kV, dose modulation. CTs
and MRIs were anonymized and scored in random order by 2 independent observers using the validated CF-CT score and an equivalent CF-MRI scoring system. BE,
TA and other structural components were scored. Scores are expressed as % of the maximal score. Mean scores of both observers were used for comparisons
between CT and MRI scores. Statistics: Pearson; Intra class coefficient (ICC); Bland-Altman plots. Results mean (range).
RESULTS: Interobserver variability (ICC): CT-BE (0,931); MRI-BE (0,892); CT-TA (0,917); MRI-TA (0,677) Correlation between CT-BE score and MRI-BE score
(R=0,940, p=0,0001); between CT-TA and MRI-TA (r=0,511, p=0,005). Bland-Altman plots showed that MRI systematically underestimated severity of BE relative
to CT. Moreover the Intraobserver variability was greater for MRI than CT (CT-BE vs.MRI-BE, 0,925 vs. 0,838). This head to head comparison between CT and MRI
shows that there is good agreement between observers to identify structural abnormalities both on CT as on MRI and that CT-BE and MRI-BE correlated well.
However the sensitivity of MRI to detect BE is still inferior to that of CT. The measurement of TA by MRI was not reliable.
CONCLUSION: MRI is less sensitive compared to CT to detect BE and TA. We are currently testing alternative image analysis techniques to improve the sensitivity of
MRI to monitor CF lung disease.
CLINICAL RELEVANCE/APPLICATION: MRI shows to be less accurate compared to CT in the evaluation of CF lung disease, especially for AT. Further studies are
needed to define the role of lung MR in CF follow-up
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
- …
