1,720,961 research outputs found
Role of magnetic resonance in characterising extrahepatic cholangiocarcinomas
Full text linkPURPOSE: The purpose of this study was to evaluate the accuracy of magnetic resonance (MR) in correctly locating and characterising biliary strictures in patients affected by extrahepatic cholangiocarcinoma, identify findings suggestive of the disease, identify lesions with similar MR features and possible criteria for differential diagnosis and establish prospective MR accuracy in diagnosis of malignant obstruction of extrahepatic bile ducts. MATERIALS AND METHODS: We retrospectively reviewed the MR examinations of 39 patients affected by extrahepatic cholangiocarcinoma confirmed by histology or cytology. The studies were evaluated for the following parameters: site of obstruction (hilar, proximal or distal), presence of intra- or extrahepatic dilation of bile ducts, morphology of ductal stenosis (gradual tapering or abrupt ending), morphology of the lesion (mass like or circumferential), dimension, signal intensity before contrast medium administration and lesion enhancement after administration of contrast medium. Finally, we assessed the most useful sequence for the diagnosis. In order to evaluate MR accuracy in the diagnosis of malignant obstruction of extrahepatic bile ducts, we prospectively reviewed MR examinations of 74 patients affected by obstructive jaundice (55 malignant lesions and 19 inflammatory lesions). MR diagnosis was compared with histology or cytology considered as the gold standard. RESULTS: MR allowed identification and localisation of 41/41 extrahepatic cholangiocarcinomas. Fifty-four percent of the lesions showed gradual duct tapering; the remaining lesions showed an abrupt ending. Fifty-six percent of the lesions appeared as a circumferential thickening (infiltrative growth); the remaining lesions had a mass-like appearance (expansile growth). Most lesions were hypo- (49%) or isointense (49%) in T1-weighted sequences and hyper- (49%) or isointense (51%) in T2-weighted sequences. Ninety-five percent of the lesions did not enhance significantly in the arterial phase while 98% showed late enhancement (10 min). The most diagnostic sequence (in 76% of cases) was the late-phase gradient-echo (GRE) T1 fat-saturated sequence. MR had good sensitivity (91%) but poor specificity (47%) in characterising stenosis as malignant, given the large number (10/19) of benign lesions evaluated as neoplastic lesions. CONCLUSIONS: MR almost always identified the cause of stenosis and suggested its neoplastic nature if it exhibited a mass-like appearance (extraductal or growing into the choledochus). On the other hand, lesions with parietal thickening, particularly if smaller than 1 cm, require endoscopic cytology or histology because of the high risk of unnecessary procedures for benign lesions
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
Branch-duct intraductal papillary mucinous neoplasms of the pancreas: to operate or not to operate? Results of a prospective protocol on the management of 109 consecutive patients.
No full textBACKGROUND:
Branch-duct intraductal papillary mucinous neoplasms (BD-IPMNs) of the pancreas are reported to be less aggressive than the main-duct type. Hence, less aggressive treatment has been proposed for the former.
AIM:
To evaluate the effectiveness of a follow-up protocol for BD-IPMNs.
DESIGN:
Prospective study.
SETTING:
An academic tertiary referral centre.
PATIENTS:
From 2000 to 2003, 109 patients with BD-IPMNs underwent trans-abdominal ultrasound and magnetic resonance cholangiopancreatography with secretin. Patients who presented malignancy-related parameters (size >3.5 cm, nodules, thick walls, carbohydrate antigen 19.9 level >25 U/l, recent-onset or worsened diabetes) and/or complained of symptoms were submitted to surgery (arm A). All asymptomatic patients without suspicion of malignancy were followed up according to a 6-month clinical-radiological protocol (arm B).
MAIN OUTCOME MEASURES:
The effectiveness of conservative management of BD-IPMNs.
RESULTS:
20 (18.3%) patients underwent surgery (arm A); pathological diagnosis of BD-IPMNs was always confirmed. 89 (81.7%) patients were followed up for a median of 32 months (arm B); of these, 57 (64%) patients had multifocal disease. After a mean follow-up of 18.2 months, 5 (5.6%) patients showed an increase in lesion size and underwent surgery. The pathological diagnosis was branch-duct adenoma in three patients and borderline adenoma in two.
CONCLUSIONS:
Surgery is indicated in <20% of cases of BD-IPMNs, and, in the absence of malignancy-related parameters, careful non-operative management seems to be safe and effective in asymptomatic patients. Although observation for a longer time is needed to confirm these results, our findings support the guidelines recently recommended by the International Association of Pancreatology
Pelvic endometriosis: US and MRI features
No full textEndometriosis represents a common and important clinical problem of women of childbearing age. It is a disabling disorder manifesting with pain and infertility. The exact pathogenesis of the disease remains unclear, despite the different theories that have been formulated. The literature on endometriosis is extensive, but often in regard to classic endometrioma. It is surprising that, to the best of our knowledge, the many radiologic features of extraovarian endometriosis have not been well documented thus far. Although ultrasound (US) remains the imaging modality of choice in the radiologic evaluation of female patients with pelvic pain, the role of magnetic resonance imaging (MRI) in the evaluation of abdominal pain is expanding. In the young patient, MRI may be performed if a gynecologic disorder is not suspected at first, especially if US findings are equivocal or the abnormality extends beyond the field of view of the sonographic probe. Moreover, MRI is useful whenever further characterization of pelvic disorder is required. In fact, many causes of pelvic disorders and of endometriosis in particular demonstrate characteristic MRI findings. For these reasons, in this work we describe the protean US and MRI appearances of endometrial foci as encountered in daily experience
Solid hypervascular liver lesions: accurate identification of true benign lesions on enhanced dynamic and hepatobiliary phase magnetic resonance imaging after gadobenate dimeglumine administration.
No full textPURPOSE:To evaluate hepatobiliary phase magnetic resonance imaging with gadobenate dimeglumine for differentiation of benign hypervascular liver lesions from malignant or high-risk lesions.METHODS AND MATERIALS:Retrospective assessment was performed of 550 patients with 910 hypervascular lesions (302 focal nodular hyperplasia [FNH], 82 nodular regenerative hyperplasia [NRH], 59 hepatic adenoma or liver adenomatosis [HA/LA], 329 hepatocellular carcinomas [HCC], 12 fibrolamellar-HCC [FL-HCC], 21 peripheral cholangiocarcinomas [PCC], 105 metastases). Imaging was performed before and during the arterial, portal-venous, equilibrium, and hepatobiliary phases after gadobenate dimeglumine administration (0.05 mmol/kg). Histologic confirmation was available for ≥1 lesion per patient, except for patients with suspected FNH (diagnosis based on characteristic enhancement/follow-up). Lesion differentiation (benign/malignant) on the basis of contrast washout and lesion enhancement (hypo-/iso-/hyperintensity) was assessed (sensitivity, specificity, accuracy, PPV, and NPV) relative to histology or final diagnosis.RESULTS:On portal-venous or equilibrium phase images, washout was not seen for 208 of 526 (39.5%) malignant (HCC, FL-HCC, PCC, metastases) and high-risk (HA/LA) lesions. Conversely, only 5 of 384 (1.3%) true benign lesions (FNH/NRH) showed washout. Taking washout as indicating malignancy, the sensitivity, specificity, and accuracy for malignant lesion identification during these phases was 61.8%, 98.7%, and 77.4%. On hepatobiliary phase images, 289 of 302 FNH, 82 of 82 NRH, 1 of 59 HA or LA, 62 of 341 HCC or FL-HCC, and 2 of 105 metastases were hyperintense or isointense. Taking iso- or hyperintensity as an indication for lesion benignity, the sensitivity, specificity, accuracy, PPV, and NPV for benign lesion identification was 96.6%, 87.6%, 91.4%, 85.1%, and 97.3%, respectively.CONCLUSIONS:Hepatobiliary phase imaging with gadobenate dimeglumine is accurate for distinguishing benign lesions from malignant or high-risk lesions. Biopsy should be considered for hypointense lesions on hepatobiliary phase images after gadobenate dimeglumine
Role of echocardiography and cardiac MRI in depicting morphological and functional imaging findings useful for diagnosing hypertrophic cardiomyopathy
No full textPURPOSE:
Hypertrophic cardiomyopathy (HCM) is a hereditary disease characterised by primary hypertrophy of the left and/or right ventricle. The reference standard for imaging diagnosis is echocardiography. The aim of our study was to prospectively compare the diagnostic accuracy of echocardiography and cardiac magnetic resonance (MR) imaging in patients with HCM.
MATERIALS AND METHODS:
Twenty-two consecutive patients with a known diagnosis of HCM were prospectively evaluated, with echocardiography and cardiac MR imaging performed within 2 weeks of each other (mean interval 7 days, range 2-14 days). Two experienced radiologists blinded to the previous clinical and imaging findings separately reviewed the images. The following parameters were calculated for both techniques: myocardial mass, wall thickness, end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), systolic anterior motion (SAM) of the mitral valve and degree of myocardial fibrosis (based on the ultrasonic reflectivity at echocardiography and degree of late enhancement at cardiac MR imaging). The statistical correlation was calculated with Student's t test, Spearman coefficient and Fisher's exact test. A value of p<0.05 was considered significant.
RESULTS:
The diagnosis of HCM was confirmed in all patients with both techniques, with absolute agreement in terms of the site of disease. The mean value of myocardial mass presented a statistically significant difference between the two techniques (114 g, p<0.001). In contrast, a nonsignificant difference between echocardiography and cardiac MR imaging was found for EDV (102 ml vs 111 ml; p=0.31), ESV (30 ml vs 38 ml; p=0.1), EF (74% vs 68%, p=0.5), SAM (p=0.1) and myocardial fibrosis (p=0.15).
CONCLUSIONS:
Cardiac MR imaging correlates well with echocardiography in defining the morphological and functional parameters useful for the imaging diagnosis of HCM and therefore, in selected cases (poor acoustic window, doubtful echocardiography findings), it may be a valid alternative to echocardiography
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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