1,720,969 research outputs found
A Statistical Approach to Assess the Robustness of Radiomics Features in the Discrimination of Mammographic Lesions
Full text linkDespite mammography (MG) being among the most widespread techniques in breast
cancer screening, tumour detection and classification remain challenging tasks due to the high
morphological variability of the lesions. The extraction of radiomics features has proved to be a
promising approach in MG. However, radiomics features can suffer from dependency on factors
such as acquisition protocol, segmentation accuracy, feature extraction and engineering methods,
which prevent the implementation of robust and clinically reliable radiomics workflow in MG. In
this study, the variability and robustness of radiomics features is investigated as a function of lesion
segmentation in MG images from a public database. A statistical analysis is carried out to assess
feature variability and a radiomics robustness score is introduced based on the significance of the
statistical tests performed. The obtained results indicate that variability is observable not only as
a function of the abnormality type (calcification and masses), but also among feature categories
(first-order and second-order), image view (craniocaudal and medial lateral oblique), and the type
of lesions (benign and malignant). Furthermore, through the proposed approach, it is possible to
identify those radiomics characteristics with a higher discriminative power between benign and
malignant lesions and a lower dependency on segmentation, thus suggesting the most appropriate
choice of robust features to be used as inputs to automated classification algorithms
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
U-net based approach for pectoralis muscle segmentation in digital mammography
No full textAccurate segmentation of the breast is a fundamental step in computer-aided diagnosis (CAD) systems for mammography. In particular, several tasks, such as the classification of breast density, evaluation of correct positioning of the breast, and automatic detection and classification of suspicious lesions, preliminarily require an accurate segmentation of the pectoralis muscle. This study aims to propose an automatic breast segmentation algorithm that combines traditional methods with Deep Learning methods limited only to the border region between the muscle and the breast. This type of approach allows for reducing the risk of having good overall accuracy in multi-class classification that does not reflect adequate accuracy with respect to small classes, such as the pectoralis muscle in a mammographic image. The U-Net network was therefore implemented on patches extracted along the straight line with which the muscle-breast edge was first estimated. The predicted patches are repositioned to perform an edge refinement and obtain the total breast mask, using histogram-based thresholding to segment the background from the breast. The results show Dice values equal to 0.848 ± 0.196 and Jaccard index equal to 0.774 ± 0.227 for the single patches, and Dice values equal to 0.971 ± 0.011 and Jaccard index equal to 0.944 ± 0.022 for the entire breast segmentation
Circuital modelling in muscle tissue impedance measurements
Full text link: Electrical impedance spectroscopy (EIS) stands as a widely employed characterization technique for studying muscular tissue in both physio/pathological conditions. This methodology commonly involves modeling tissues through equivalent electrical circuits, facilitating a correlation between electrical parameters and physiological properties. Within existing literature, diverse equivalent electrical circuits have been proposed, varying in complexity and fitting properties. However, to date, none have definitively proven to be the most suiTable for tissue impedance measurements. This study aims to outline a systematic methodology for EIS measurements and to compare the performances of three widely used electrical circuits in characterizing both physiological and pathological muscle tissue conditions. Results highlight that, for optimal fitting with electrical parameters relevant to tissue characterization, the choice of the circuit to be fitted closely hinges on the specific measurement objectives, including measurement parameters and associated physiological features. Naturally, this necessitates a balance between simplicity and fitting accuracy
A general framework for the assessment of scatter correction techniques in digital mammography
No full textScattered radiation negatively impacts radiographic imaging, with particular regard to mammography. In clinical practice, anti-scatter grids are exploited for this purpose; however, anti-scatter grids may also degrade the image quality, since they remove part of the useful primary radiation with the consequent increase of the dose to be administered to the patient. A suitable digital scatter correction method could tackle the limits imposed by such grids with a great impact on diagnosis. The main contribution of this study is the development of a general framework for the assessment of digital scatter correction techniques in mammography. To this aim, the formation process of both primary and scattered image is described on the basis of a systems-theory approach. Through a simulation of the radiological process, a reference model of the primary image is obtained and used as ground truth to compare the intensities of images obtained by applying a deconvolution-based digital scattering correction technique. Then, an experimental case study on breast phantom images is carried out to assess the scatter correction using different Point Spread Functions (PSFs) (Gaussian and Hyperbolic) with varying parameters values. A central issue was the identification of a spatially variant PSF to model the scattered radiation. The results demonstrate that the proposed approach enables the assessment and the comparison of different PSF kernels employed for scatter correction; in particular, our procedure shows that rather low relative errors are obtained ([-0.5;0.5]) for both the PSFs tested and that Gaussian ones are more sensitive to variations in their parameters
3D Dental Reconstruction with Photogrammetry Technology
No full textIn the dental field, the use of digital technologies for
scanning of the hard and soft tissues of the mouth is becoming
more and more widespread. The availability of digital 3D models
of the dental arches allows to plan treatments and to show
the results in advance, increasing patient confidence. However,
currently in clinical practice, the accuracy of digital models,
although very satisfactory, does not reach that of traditional
impressions. It also requires the use of technologies that simplify
the hardware structure, making the intraoral acquisition device
more manageable and comfortable. The purpose of this study is to
evaluate how photogrammetry technology, commonly and widely
used and very effective in other sectors, can be adapted to the
dental field, starting from the reconstruction of a dental plaster
cast. By comparing the 3D model obtained with the proposed
technology with a 3D model obtained using the leading top
player intraoral scanners on the market, comparable results were
obtained in terms of reconstruction performance. Both from the
comparison of the spatial alignment and from the comparison
of the shape, a certain overlap and equality between the two
3D models emerge. These results suggest that this technology
could represent a valid solution for the 3D models reconstruction
also in the dental field, overcoming the limitation of technologies
currently used on the market in this field
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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