1,721,031 research outputs found
Prenatal diagnosis of Seckel Syndrome on 3-dimensional sonography and magnetic resonance imaging.
No full textSuperparamagnetic iron oxide nanocolloids in MRI studies of neuroinflammation
No full textIron oxide (IO) nanocolloids are being increasingly used to image cellular contribution to neuroinflammation using MRI, as these particles are capable of labeling circulating cells with phagocytic activity, allowing to assess cell trafficking from the blood to neuroinflammation sites. The use of IOs relies on the natural phagocytic properties of immune cells, allowing their labeling either in vitro or directly in vivo, following intravenous injection. Despite concerns on the specificity of the latter approach, the widespread availability and relatively low cost of these techniques, coupled to a sensitivity that allows to reach single cell detection, have promoted their use in several preclinical and clinical studies.
In this review, we discuss the results of currently available preclinical and clinical IO-enhanced MRI studies of immune cell trafficking in neuroinflammation, examining the specificity of the existing findings, in view of the different possible mechanisms underlying IO accumulation in the brain. From this standpoint, we assess the implications of the temporal and spatial differences in the enhancement pattern of IOs, compared to gadolinium based contrast agents, a clinically established MRI marker blood-brain barrier breakdown. While concerns on the specificity of cell labeling obtained using the in-vivo labeling approach still need to be fully addressed, these techniques have indeed proved able to provide additional information on neuroinflammatory phenomena, as compared to conventional Gadolinium-enhanced MRI
Accuracy of neurosonography and MRI in clinical management of fetuses referred with central nervous system abnormalities
No full textOBJECTIVE:
To assess the accuracy of expert neurosonography (two- and three-dimensional NSG) in the characterization of major fetal central nervous system (CNS) anomalies seen at a tertiary referral center and to report the differential clinical usefulness of magnetic resonance imaging (MRI) used as a second-line diagnostic procedure in the same cohort.
METHODS:
This was a retrospective analysis of all 773 fetuses with confirmed CNS abnormalities referred to our center between 2005 and 2012. The following variables were analyzed: gestational age at NSG and MRI, NSG and MRI diagnoses, indication for MRI (confirmation of NSG findings; diagnostic doubt; search for possible additional brain anomalies), association with other malformations, diagnostic accuracy of NSG vs MRI (no additional clinical value for either MRI or NSG; additional information with clinical/prognostic significance on MRI relative to NSG; additional information with clinical/prognostic significance on NSG relative to MRI, NSG and MRI concordant but incorrect) and final diagnosis, which was made at autopsy or postnatal MRI/surgery.
RESULTS:
CNS malformations were associated with other anomalies in 372/773 (48.1%) cases and were isolated in the remaining 401 (51.9%) cases. NSG alone was able to establish the diagnosis in 647/773 (83.7%) cases. MRI was performed in 126 (16.3%) cases. The indication for MRI was: confirmation of NSG diagnosis in 59 (46.8%) cases; diagnostic query (in the case of inconclusive or uncertain finding on NSG) in 20 (15.9%) cases; search for possible additional brain anomalies in 47 (37.3%) cases. NSG and MRI were concordant and correct in 109/126 (86.5%) cases. Clinically relevant findings were evident on MRI alone in 10/126 (7.9%) cases (1.3% of the whole population) and on NSG alone in 6/126 (4.8%) cases; in all six of these cases, MRI had been performed at < 24 weeks of gestation. In one case, both NSG and MRI diagnoses were incorrect. The main type of malformation in w ich MRI played an important diagnostic role was space-occupying lesions, MRI identifying clinically relevant findings in 42.9% (3/7) of these cases.
CONCLUSIONS:
(1) In a tertiary referral center with good NSG expertise in the assessment of fetal CNS malformations, MRI is likely to be of help in a limited proportion of cases; (2) MRI is more useful after 24 weeks of gestation; (3) the lesions whose diagnosis is most likely to benefit from MRI are gross space-occupying lesions
Current status and future prospective of neuroimaging for epilepsy
No full textAlthough the diagnosis of epilepsy remains mainly clinical, Magnetic Resonance Imaging (MRI) plays a crucial role in the detection of lesions that can cause epilepsy, with high impact on the diagnostic work-up as well as on therapeutic planning. Morphologic MR imaging is still the main technique for identifying lesions responsible for the epilepsy, providing images with high spatial resolution, excellent soft-tissue contrast, and multiplanar view. Quantitative MR image analysis (segmentation, voxel-based morhometry), based on 3D T1-weighted images, offers an objective means of analyzing MR images thereby improving the capability of detecting subtle lesions, often interpreted as negative by qualitative assessment of the morphologic MR imaging. Diffusion tensor imaging allows the quantification of water molecules diffusion and characterizes the degree and direction of anisotropy. Areas of abnormal diffusion, responsible for epilepsy, may be related to occult dysgenesis, or to acquired damage, resulting in neuronal loss, gliosis, and extracellular space expansion; these changes often result in reduced anisotropy and in an increase in mean diffusivity. Magnetic resonance spectroscopy provides information about the biochemical environment of the brain, thereby helping in lateralizing the epilepsy focus. Functional MR imaging is used for lateralizing language functions, and also for surgical planning predicting functional deficits following epilepsy surgery. The interpretation of MR data should always be done by a neuroradiologist expert in the field of epilepsy imaging, trying to correlate the images with clinical and electrophysiological data
Erratum: Choroid plexus carcinoma: Prenatal characterization by 3-dimensional sonography and magnetic resonance imaging, perinatal management, and natural history (Journal of Ultrasound in Medicine (2012) 31 (337-339))
No full textPapillomas of the choroid plexus are rare neoplasms of neuroectodermal origin. They represent less than 5% of all central nervous system tumors in pediatric patients, with 10% to 20% of them occurring during the first year of life.1 Choroid plexus carcinomas, which are even rarer, derive from choroid plexus epithelium and are characterized by papillary and intraventricular growth. As for their site of origin, 50% are located in the lateral ventricles; 40% arise in the fourth ventricle; 5% originate in the third ventricle; and the remaining 5% are multifocal. Choroid plexus carcinomas are often associated with secondary hydrocephalus and increased intracranial pressure due to both obstruction of major foramina and overproduction of cerebrospinal fluid.2 These tumors represent exceedingly rare brain malignant neoplasms, and a database of all cases reported in the pediatric literature up to the year 2004 describes 347 cases.3 However, to the best of our knowledge, such a tumor was described only 3 times in a fetus.4,5 We report the second prenatal diagnosis of choroid plexus carcinoma in a 33-week fetus, focusing on the imaging features of the tumor, which was assessed by 2-dimensional (2D) and 3-dimensional (3D) sonography and magnetic resonance imaging (MRI), and reporting its unfortunately limited perinatal management and course
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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