1,720,975 research outputs found
L’eterogeneità perfusionale: un biomarker prognostico per il cancro del polmone non a piccole cellule (NSCLC)
No full textL’introduzione in oncologia di nuove terapie, in particolare quelle a bersaglio molecolare, ha condotto a notevoli progressi terapeutici, determinando miglior controllo del tumore, selettività terapeutica, ridotta tossicità. Tuttavia la prognosi per i pazienti affetti da tumore polmonare non a piccole cellule (NSCLC) in stadio avanzato risulta tuttora molto severa. Sebbene il più importante fattore prognostico sia attualmente costituito dallo stadio del tumore, la sopravvivenza di pazienti affetti da NSCLC e appartenenti allo stesso stadio risulta ampiamente variabile. Per queste ragioni, è necessario identificare marcatori prognostici più efficaci che siano in grado di stabilire quali tumori saranno sensibili o resistenti alle terapie. Questo condurrebbe ad una migliore gestione e stratificazione dei pazienti affetti da NSCLC, con notevoli implicazioni nella scelta dei trattamenti. L’analisi dell’eterogeneità neoplastica nei pazienti NSCLC, caratterizzata attraverso l’analisi strutturale mediante Tomografia Computerizzata (TC), ha mostrato notevoli potenzialità nel predire l’aggressività di un tumore. Anche più promettente è l’analisi dell’eterogeneità funzionale in grado di mettere in luce non solo le anomalie strutturali ma anche le disomogeneità funzionali presenti all’interno di un tumore. Tra le tecniche di imaging funzionale, particolare rilievo sta assumendo la TC perfusionale (TCp), che permette l’identificazione di pattern vascolari anomali, consentendo una valutazione precoce della risposta alle terapie citostatiche. In questo lavoro retrospettivo, valutiamo se alcuni indicatori, calcolabili a partire dalle mappe di valori perfusionali ottenute tramite TCp, possano essere utilizzati come marcatori prognostici. I risultati rilevano una coppia di indicatori in grado di separare pazienti affetti da NSCLC con diversa aspettativa di sopravvivenza. Viene confermata la comune aspettativa che una maggiore eterogeneità correli con una maggiore aggressività, riflettendosi gravemente sulla sopravvivenza dei pazienti. Si può quindi concludere che la misura emodinamica dell’eterogeneità tumorale rappresenti un significativo e oggettivo fattore prognostico, con possibili ricadute cliniche della TCp
DCE-CT in lung cancer: perfusion characterisation of adenocarcinoma and squamous carcinoma subtypes
No full textPurpose: To evaluate tumour baseline characteristics in blood flow (BF) values of two lung cancer subtypes, adenocarcinoma (AC) and squamous cell carcinoma (SCC). In addition, since literature shows discordant results, we also investigate possible motivations, so as to find out a clearer outcome.
Methods and Materials: 27 patients (age range 36-81 years) with primary NSCLC, subdivided into 20 AC and 7 SCC, were enrolled in this study and underwent a CT perfusion at the diagnosis stage. BF values were computed according to the maximum slope method and values undergoing high fitting errors were automatically removed. The one-tail Welch's t-test (p<0.001) was employed for statistical assessment.
Results: At baseline, mean BF values of AC group [81.4±30.1] result significantly greater than those of SCC subtype [59.6±31.7] (p<<10-5). Excluding unreliable BF values enforced the outcome. However, a few cases deviate from the mean value of the corresponding histological group. Two SCC lesions present a higher perfusion because of beam hardening artefacts coming from the pulmonary artery. Analogously, four AC cases show a lower perfusion, two of which are large and central lesions. The others, in the subpleural parenchyma, have a predominant pulmonary component underestimated by a delayed acquisition.
Conclusion: At diagnosis, AC histological type has a significantly greater perfusion than SCC one. This clear behaviour may be attenuated by lesion position, central or peripheral, pulmonary artery artefacts and not appropriate acquisition protocol. Although these findings are clear, they should be enforced by a larger dataset, being of relevant importance for treatment strategies
Automatic visual-like classification of lung tumour heterogeneity in DCE-CT sequences
No full textPurpose: Tumour heterogeneity is an important prognostic factor, as high intra-tumour heterogeneity showed to be associated with higher tumour grades. However, its assessment is still mostly accomplished subjectively through visual procedure. This work presents an automatic approach to classify the heterogeneity levels in lung tumour as performed through visual analysis.
Methods and Materials: 40 datasets referring to 13 patients (age range 36-81 years) with NSCLC, who underwent axial DCE-CT, were considered. Two 25-year experienced Readers chose the most representative slices in the DCE-CT sequences, outlined each lesion and its most significant regions. Then, each slice was assigned a class, according to a proper taxonomy for heterogeneity levels previously defined: homogeneous, macro-inhomogeneous (i.e., different homogeneities together), and micro-inhomogeneous. A statistical voxel-based index was devised to quantify the heterogeneity, then represented in colorimetric maps. The values were grouped into regions subsequently compared with those drawn by radiologists.
Results: Results for the three classes were computed in terms of specificity (SP) and sensitivity (SE). Our approach proved to be extremely specific, mostly for homogeneous (SE=77%, SP=93%) and macro-inhomogeneous (SE=75%, SP=90%) tissues. On the other hand, the most indefinite micro-inhomogeneous tissue also shows a high specificity (SE=86%, SP=87%).
Conclusion: The approach developed allows an automatic classification of heterogeneities, with a reduction of both intra- and inter-observer variability. This represents a novel approach acting as a second radiologist in the heterogeneity assessment, which could yield a great benefit for patient stratification and constitutes a valid tool to assist radiologists in daily clinical activities
An empirical model for predicting insects' diapause termination and phenology: An application to Cydia pomonella
No full textDiapause is a vital survival strategy for insects, enabling them to conserve energy and endure adverse conditions. Understanding how diapause affects insect phenology and population dynamics is crucial for the effective management of insect pests. Predictive pest phenological models can be invaluable tools for providing essential information to support management strategies. This study presents a modelling framework to incorporate diapause into phenological models when biological information on variables regulating and functions describing diapause induction and termination are lacking or limited. In our framework, insect phenology is divided into a set of phases characterized by specific events (diapause induction and termination) and processes (development of diapausing and post-diapausing biological stages). The phenology is simulated by a stage-structured model based on the Kolmogorov equation, and the temperature-dependent development rate functions are described by the Briere functional form. Our modelling framework was tested on a case study involving the prediction of the phenology of the codling moth, (Cydia pomonella L. 1758). Model calibration and validation were performed using four time-series adult trap catch data collected in the Emilia Romagna Region from 2021 to 2023. The calibration procedure allowed obtaining realistic parameters related to the temperature threshold triggering diapause termination and the development rate function of post-diapausing larvae and pupae. Model validation proved successful in simulating both the initial emergence and the overall phenological patterns of adults across the three observed generations. The methodological framework proposed here aims to facilitate the introduction of diapause in phenological models improving also their predictive abilities. The model may serve as an accurate and knowledge-based tool for planning and implementing pest monitoring and control actions based on the realistic predictions provided by the model on the phenological status of the pest
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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