1,720,990 research outputs found
Photon-counting detector computed tomography : Paradigm shift in cardiac CT imaging
No full textBackground: The introduction of photon-counting detector computed tomography (PCD-CT) heralds a new generation of cardiac imaging. Objectives: This review discusses the current scientific literature to determine the incremental value of PCD-CT in cardiac imaging. Methods: Discussion of currently available literature regarding cardiac PCD-CT from a radiological perspective. Results: Since its market introduction in 2021, numerous studies have explored the advantages of this new technology in the field of cardiac imaging, including improved image quality through superior spatial resolution, a higher contrast-to-noise ratio, reduced artifacts, and lower radiation dose. Conclusion: While preliminary studies have been promising, it remains to be seen how the advantages of PCD-CT will affect clinical guidelines for cardiac CT
Intra-individual comparison of epicardial adipose tissue characteristics on coronary CT angiography between photon-counting detector and energy-integrating detector CT systems
No full textPurpose: To explore the potential differences in epicardial adipose tissue (EAT) volume and attenuation measurements between photon-counting detector (PCD) and energy-integrating detector (EID)-CT systems. Methods: Fifty patients (mean age 69 +/- 8 years, 41 male [82 %]) were prospectively enrolled for a research coronary CT angiography (CCTA) on a PCD-CT within 30 days after clinical EID-based CCTA. EID-CT acquisitions were reconstructed using a Bv40 kernel at 0.6 mm slice thickness. The PCD-CT acquisition was reconstructed at a down-sampled resolution (0.6 mm, Bv40; [PCD-DS]) and at ultra-high resolutions (PCD-UHR) with a 0.2 mm slice thickness and Bv40, Bv48, and Bv64 kernels. EAT segmentation was performed semi-automatically at about 1 cm intervals and interpolated to cover the whole epicardium within a threshold of -190 to -30 HU. A subgroup analysis was performed based on quartile groups created from EID-CT data and PCD-UHRBv48 data. Differences were measured using repeated-measures ANOVA and the Friedman test. Correlations were tested using Pearson's and Spearman's rho, and agreement using Bland-Altman plots. Results: EAT volumes significantly differed between some reconstructions (e.g. EID-CT: 138 ml [IQR 100, 188]; PCD-DS: 147 ml [110, 206]; P<0.001). Overall, correlations between PCD-UHR and EID-CT EAT volumes were excellent, e.g. PCD-UHRBv48: r: 0.976 (95 % CI: 0.958, 0.987); P<0.001; with good agreement (mean bias: -9.5 ml; limits of agreement [LoA]: -40.6, 21.6). On the other hand, correlations regarding EAT attenuation was moderate, e.g. PCD-UHRBV48: r: 0.655 (95 % CI: 0.461, 0.790); P<0.001; mean bias: 6.5 HU; LoA: -2.0, 15.0. Conclusion: EAT attenuation and volume measurements demonstrated different absolute values between PCD-UHR, PCD-DS as well as EID-CT reconstructions, but showed similar tendencies on an intra-individual level. New protocols and threshold ranges need to be developed to allow comparison between PCD-CT and EID-CT data
Intra-individual radiomic analysis of pericoronary adipose tissue: photon-counting detector vs energy-integrating detector CT angiography
No full textBackground: The impact of novel photon-counting detector (PCD)-CT technology on in-vivo radiomics is not fully understood. This study aimed to compare the intra-individual stability and reproducibility of pericoronary adipose tissue (PCAT) radiomic features between PCD-CT and energy-integrating detector (EID)-CT in patients undergoing coronary CT angiography (CCTA) on both systems. Methods: Patients undergoing clinically indicated CCTA on an EID-CT were prospectively enrolled for research PCD-CCTA within 30 days. Image acquisition parameters were standardized; PCD-CT datasets were reconstructed both down-sampled to 0.6 mm to match the clinical scan (PCD-CTDS) and at 0.2 mm ultrahigh-resolution mode (PCD-CTUHR). Automatic PCAT segmentation was performed; a total of 110 radiomic feature classes were extracted and compared across the three datasets (EID-CT, PCD-CTDS, and PCD-CDUHR). Feature stability was assessed using paired t-test filtered for false discoveries using Benjamini–Hochberg method, and reproducibility using intraclass correlation coefficient (ICC). Results: A total of 42 patients (34 male [81.0 %]; 67.9 ± 7.6 years) were included. Feature stability was 91 % for EID-CT vs. PCD-CTDS, but decreased for UHR datasets (EID-CT vs. PCD-CTUHR: 55 %; PCD-CTDS vs. PCD-CTUHR: 51 %). However, inter-scanner reproducibility was poor in both comparisons (EID-CT vs. PCD-CTDS median ICC: 0.43 [0.03–0.69]; EID-CT vs. PCD-CTUHR: 0.29 [0.01–0.51]). Nevertheless, reproducibility improved within PCD-CT datasets (PCD-CTDS vs. PCD-CTUHR: 0.72 [0.48–0.83]), regardless of the difference in slice thickness. Conclusions: Most PCAT radiomic features remained stable between EID-CT and PCD-CTDS, although inter-scanner reproducibility was poor, emphasizing the significant impact of detector technology. Conversely, reproducibility of features within PCD-CT datasets showed more consistent results, even when comparing standard to UHR
Das native Koronarkalk-CT als Planungswerkzeug der CT-Koronarangiographie – Effekt auf die Strahlendosis und die Bildqualität bei prospektiven EKG-getriggerten Akquisitionstechniken
No full textBei einer retrospektiven CT Koronarangiographie (cCTA) reduziert eine zuvor akquirierte Koronarkalk-CT die Strahldosis, da die Scanlänge der dosisintensiven cCTA an ihr besser geplant werden kann als am Topogramm. Unsere Studie untersucht, inwieweit dies bei Untersuchungsprotokollen mit prospektiver EKGTriggerung anwendbar ist. Hierfür wurden 182 konsekutive Patienten mit klinisch indizierter cCTA retrospektiv eingeschlossen. Alle erhielten eine native Koronarkalk-CT und eine cCTA. Ausgehend davon wurde eine Topogrammbasierte Planung simuliert. Scanlänge, Effektivdosis und Bildqualität wurden analysiert und mittels gepaarten, nicht-parametrischen Tests verglichen. Ferner wurden in Subgruppenanalysen patientenspezifische Faktoren und technische Aspekte näher untersucht. Hierbei zeigte die cCTA-Planung an der Koronarkalk- CT eine deutlich kürzere Scanlange als die Planung am Topogramm (111 vs 134 mm, p<0,001). Die Effektivdosis war bei der Topogramm-basierten cCTA 12,4% höher (3,35 mSv vs. 2,98 mSv; p<0,001). Die Gesamtdosis der Untersuchung mit Koronarkalk-CT betrug 3,26 mSv und war somit nur geringfügig niedriger als die Topogramm-basierte cCTA ohne Koronarkalk-CT (3,35 mSv). Der Effekt der Dosisreduktion durch ein Koronarkalk-CT wird allerdings deutlicher, sobald eine dosisintensivere Untersuchung nötig ist, wie beispielsweise bei adipösen Patienten (7,25 vs. 6,74 mSv, p<0,001), oder bei Patienten mit hoher Herzfrequenz, oder Arrhythmie, wodurch ein erweitertes „Padding“ notwendig ist (4,65 vs 4,12 mSv, p<0,001) und bei einer Röhrenspannung von 120 kV (6,41 vs. 6,13 mSv, p<0,001). Lediglich bei schlanken Patienten mit einem regelmäßigen Herzrhythmus und niedriger Herzfrequenz, welche mittels highpitch cCTA untersucht wurden, ist der Effekt der Dosisreduktion durch eine vorgeschaltete Koronarkalk-CT nicht gegeben (0,97 vs. 0,81 mSv , p<0,001). Hier zeigte sich der gegenteilige Effekt und die Topogramm-basierte Planung wies eine niedrigere Strahlenexposition auf. Falls die Voraussetzungen für die Akquisition einer high-pitch cCTA-Untersuchung gegeben sind, kann das Unterlassen der Koronarkalk-CT zur Gesamtdosisreduktion der Untersuchung beitragen. Ansonsten liefert ein Koronarkalk-CT einen diagnostischen und prognostischen Mehrwert und kann erfolgreich zur Strahlenreduktion durch optimale Scanlängenanpassung herangezogen werden
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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