1,720,985 research outputs found
Automated segmentation refinement of small lung nodules in CT scans by local shape analysis
No full textOne of the most important problems in the segmentation of lung nodules in CT imaging arises from possible attachments occurring between nodules and other lung structures, such as vessels or pleura. In this report, we address the problem of vessels attachments by proposing an automated correction method applied to an initial rough segmentation of the lung nodule. The method is based on a local shape analysis of the initial segmentation making use of 3-D geodesic distance map representations. The correction method has the advantage that it locally refines the nodule segmentation along recognized vessel attachments only, without modifying the nodule boundary elsewhere. The method was tested using a simple initial rough segmentation, obtained by a fixed image thresholding. The validation of the complete segmentation algorithm was carried out on small lung nodules, identified in the ITALUNG screening trial and on small nodules of the lung image database consortium (LIDC) dataset. In fully automated mode, 217/256 (84.8%) lung nodules of ITALUNG and 139/157 (88.5%) individual marks of lung nodules of LIDC were correctly outlined and an excellent reproducibility was also observed. By using an additional interactive mode, based on a controlled manual interaction, 233/256 (91.0%) lung nodules of ITALUNG and 144/157 (91.7%) individual marks of lung nodules of LIDC were overall correctly segmented. The proposed correction method could also be usefully applied to any existent nodule segmentation algorithm for improving the segmentation quality of juxta-vascular nodules
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
The LoG characteristic scale: a consistent measurement of lung nodule size in CT imaging.
No full textNodule growth as observed in computed tomography
(CT) scans acquired at different times is the primary feature to
malignancy of indeterminate small lung nodules. In this paper,
we propose the estimation of nodule size through a scale–space
representation which needs no segmentation and has high intraand
inter-operator reproducibility. Lung nodules usually appear
in CT images as blob-like patterns and can be analyzed in the
scale–space by Laplacian of Gaussian (LoG) kernels. For each
nodular pattern the scale–space signature was computed
and the related characteristic scale adopted as measurement of
nodule size. Both in vitro and in vivo validation of characteristic
scale were carried out. In vitro validation was done by 40
nondeformable phantoms and 10 deformable phantoms. A close
relationship between the characteristic scale and the equivalent
diameter, i.e., the diameter of the sphere having the same volume
of nodules, (Pearson correlation coefficient was 0.99) and, for nodules
undergoing little deformations (obtained at constant volume),
small variability of the characteristic scale was observed. The in
vivo validation was performed on low and standard-dose CT scans
collected from the ITALUNG screening trial (86 nodules) and
from the LIDC public data set (89 solid nodules and 40 part-solid
nodules or ground-glass opacities). The Pearson correlation coefficient
between characteristic scale and equivalent diameter
was 0.83–0.93 for ITALUNG and 0.68–0.83 for LIDC data set.
Intra- and inter-operator reproducibility of characteristic scale
was excellent: on a set of 40 lung nodules of ITALUNG data, two
radiologists produced identical results in repeated measurements.
The scan–rescan variability of the characteristic scale was also
investigated on 86 two-year-stable solid lung nodules (each one
observed, on average, in four CT scans) identified in the ITALUNG
screening trial: a coefficient of repeatability of about 0.9 mm was
observed. Experimental evidence supports the clinical use of the
characteristic scale to measure nodule size in CT imaging
3-D segmentation algorithm of small lung nodules in spiral CT images
No full textComputed tomography (CT) is the most sensitive
imaging technique for detecting lung nodules, and is now being
evaluated as a screening tool for lung cancer in several large samples
studies all over the world. In this report, we describe a semiautomaticmethod
for 3-D segmentation of lung nodules in CT images
for subsequent volume assessment. The distinguishing features of
our algorithm are the following. 1) The user interaction process. It
allows the introduction of the knowledge of the expert in a simple
and reproducible manner. 2) The adoption of the geodesic distance
in a multithreshold image representation. It allows the definition
of a fusion–segregation process based on both gray-level similarity
and objects shape. The algorithm was validated on low-dose CT
scans of small nodule phantoms (mean diameter 5.3–11 mm) and
in vivo lung nodules (mean diameter 5–9.8 mm) detected in the
Italung-CT screening program for lung cancer. A further test on
small lung nodules of Lung Image Database Consortium (LIDC)
first data set was also performed. We observed a RMS error less
than 6.6% in phantoms, and the correct outlining of the nodule
contour was obtained in 82/95 lung nodules of Italung-CT and in
10/12 lung nodules of LIDC first data set. The achieved results support
the use of the proposed algorithm for volume measurements
of lung nodules examined with low-dose CT scanning technique
3D Zernike shape descriptors for false positive reduction in a CAD system for lung nodules detection
No full textAppropriate 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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