1,721,114 research outputs found
CT urography: the end of IVU?
No full textA review of the literature on the diagnostic accuracy of multidetector computed tomography urography (MDCTU) and intravenous urography (IVU) reveals a lack of comparative studies. However, the available data indicate that MDCTU has a high diagnostic accuracy. MDCTU is also preferred by patients, as it does not require bowel preparation. Full acceptance of this technique by the urologist will depend on optimisation of the communication process with a careful selection of the images to be transmitted. MDCTU has a higher cost than IVU but allows some diagnostic algorithms to be simplified. The real concern potentially limiting the widespread use of MDCTU is its higher radiation dose when compared with IVU. Although low-dose protocols will soon be available, a substantial dose reduction can already be achieved by tailoring MDCTU to the clinical problem rather than using a standardised approach. Our analysis indicates that IVU will definitely lose any residual role it may still have. In our department, the last urographic procedure was performed in May 2006
Coronary CT angiography for patients with suspected coronary artery disease.
No full textNo abstract available
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
Myocardial Perfusion with Multislice Computed Tomography in Stable Angina Pectoris
No full textComputed tomographic (CT) coronary angiography is a well-established, noninvasive imaging modality for detection of coronary stenosis, but it has limited accuracy in demonstrating whether a coronary stenosis is hemodynamically significant. An additional functional test is often required because both anatomic and functional information is needed for guiding patient care. Recent developments in CT technology allow CT evaluation of myocardial perfusion during vasodilator stress, thereby providing information about myocardial ischemia. Investigators in several single-center studies have established the feasibility of performing stress myocardial perfusion CT imaging in small groups of patients and have shown that stress myocardial perfusion CT in combination with CT coronary angiography improved the diagnostic accuracy in comparison with CT coronary angiography alone. However, CT perfusion acquisition protocols must be optimized in terms of acquisition and reconstruction parameters, contrast material protocol injections, and radiation dose. Further research is needed to establish the clinical usefulness of this novel technique. The purpose of this review is to (a) provide an overview of the physiology of coronary circulation and myocardial perfusion; (b) describe the technical prerequisites, challenges, and mathematic modeling related to CT perfusion imaging; (c) note recent advances in CT scanners and CT perfusion protocols; and (d) discuss the interpretation of CT perfusion images. Finally, a review and summary of the current literature are provided, and future directions for research are discussed
Lower limbs low voltage (80 kV) CTA: lower radiation dose delivered and less contrast medium with preservation of image quality
No full textPurpose: To compare the intravascular enhancement in low dose (80 kV) CT- angiography of lower limbs performed with a reduced dose of high concentration contrast medium (CM) (75 ml of iopromide 370) in comparison with standard protocol at 100kV performed injecting a full dose of CM (100 ml).
Methods and Materials: 120 patients (84 males; mean age 71.4 years) were randomly directed in two different protocols of CT-angiography of lower limbs, performed with standard tube parameters (100kV) and administration of 100 ml of CM at 4 ml/s or with low voltage protocol (80 kV) with injection of 75 ml of CM at 3 ml/s. In each patient density values of 4 region of interest (ROI) at the level of the abdominal aorta, popliteal artery, of a vessel of the leg ad in a psoas muscle were measured. Risk factors, serum creatinine, the signal to noise ratio and x-ray dose (DLP) were also registered.
Results: The density values of aorta were significantly higher in 80 kV protocol in comparison with the standard protocol (P=0.001); no statistically significant differences were noted in the vascular enhancement of popliteal or leg artery. There was no statistically significant difference (P = 0.152) in image quality measured with SNR. The DLP in the 80 kV protocol was significantly lower than the standard approach (P < 0.05).
Conclusion: 80 kV CT angiography of lower limbs allows to significantly reducing the amount of administered contrast medium preserving the image quality and lowering the radiation dose of about 30%
Accuracy of Semi Automated Workflow in Reconstruction of CT Angiography prior to Transcatheter Aortic Valve Implant
No full text- …
