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Role of the advanced MRI sequences in predicting the outcome of preterm neonates
No full textAIM
The aim of the project is to evaluate the role of advanced MRI sequences
(susceptibility weight imaging (SWI), diffusion tensor imaging (DTI), and arterial
spin labeling (ASL) perfusion) in detecting early changes that affect preterm neonatal
brain, especially in those patients without lesions at conventional MRI or with small
brain injuries (i.e. low grade germinal matrix-intraventricular hemorrhage (GMHIVH)),
and to correlate these subtle brain abnormalities with neurodevelopmental
outcome at 24 months.
METHODS
Since November 2015 until June 2017, 287 preterm neonates and 108 term neonates
underwent a 3T or 1.5T MRI study at term corrected age (40±1 weeks). SWI, DTI
and ASL sequences were performed in all neonates. SWI sequences were evaluated
using both a qualitative (SWI venography) and quantitative (Quantitative
Susceptibility Map analysis (SWI-QSM)) approach. DTI data were analyzed using a
Tract-Based Spatial Statistics analysis (TBSS). ASL studies were processed to
estimate Cerebral Blood Flow (CBF) maps. Perinatal clinical data were collected for
all neonates. Neurodevelopmental data were evaluated at 24 months in 175 neonates
using 0-2 Griffiths Developmental Scales.
RESULTS
The analysis performed on SWI-venography revealed differences in subependymal
veins morphology between preterm and term neonates with normal brain MRI, with
a higher variability from the typical anatomical pattern in preterm neonates. The same
analysis performed in preterm neonates with GMH-IVH revealed that the anatomical
features of subependymal veins may play a potential role as predisposing factor for
GMH-IVH. Moreover, the SWI-QSM analysis revealed a greater paramagnetic
susceptibility in several periventricular white matter (WM) regions in preterm
neonates with GMH-IVH than in healthy controls. This finding is likely related to the
accumulation of hemosiderin/ferritin following the diffusion of large amounts of
intraventricular blood products into the WM, and it is also supposed to trigger the
cascade of lipid peroxidation and free radical formation that promote oxidative and
inflammatory injury of the WM in neonatal brain after GMH-IVH. The TBSS
analysis confirmed that microstructural WM injury can occur in preterm neonates
with low grade GMH-IVH even in the absence of overt signal changes on
conventional MRI, with different patterns of WM involvement depending on
gestational age. Moreover, the distribution of these WM microstructural alterations after GMH-IVH correlates with specific neurodevelopmental impairments at 24
months of age. Finally, the analysis of brain perfusion at term-corrected age revealed
lower CBF in preterms with sub-optimal neuromotor development, reinforcing the
hypothesis that impaired autoregulation of CBF may contribute to the development
of brain damage in preterm neonates.
CONCLUSION
Advanced MRI sequences can assist the standard perinatal brain imaging in the early
diagnosis of preterm neonatal brain lesions and can provide new insights for
predicting the neurodevelopmental trajectory. However, detailed and serial imaging
of carefully chosen cohorts of neonates coupled with longer clinical follow-up are
essential to ensure the clinical significance of these novel findings
Il "sistema Vesuvio" tra osservazioni, emozioni e scienza.
No full textIl saggio esamina il "sistema Vesuvio" tra Settecento e Ottocento, analizzando la posizione di alcuni studiosi e viaggiatori. La variegata percezione del Vesuvio trova riscontro nelle diverse prospettive, sino alla moderna lettura di sistema integrato nel quale occorre tener conto di tutte le sue componenti in un'ottica moderna ed ecosistemica
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
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