3,306 research outputs found
Uncertainty as key element in the analysis of X–ray angiography images
The X–ray angiography images are routinely used to assess the blood vessels. The
acquisition procedure considers a medical imaging system which allows obtaining views of the
vessel while the blood flows thought them. The X–ray source is influenced on the region to be
viewed and then, the projection of the all anatomical structures in the champ of view is shown
through an image intensifier. The information of the blood vessel is impacted for the other
structures. Additionally, the blood and the contrast product required in the acquisition are not
mixed homogeneously, producing artifacts in the images. Finally, the noise is also an impact
factor in the quality of the angiography images. In the coronary vessel case, the branches of the
network are superposed. In this paper, an enhancement procedure to diminish the uncertainty
associated to X–ray angiography images is reported. The relation between two versions of the
angiograms is determined using a fuzzy connector considering that this relation diminishes the
images intrinsic uncertainty. These versions correspond with images filtered with low-pass and
high-pass image filters, respectively. The technique is tested with images of the coronary and
kidney vessels. The qualitative results show a good enhanced of the angiography images
Semi-automatic detection of the evolutionary forms of visceral leishmaniasis in microscopic blood smears
Leishmaniasis is a complex group of diseases caused by obligate unicellular and
intracellular eukaryotic protozoa of the leishmania genus. Leishmania species generate diverse
syndromes ranging from skin ulcers of spontaneous resolution to fatal visceral disease. These
syndromes belong to three categories: visceral leishmaniasis, cutaneous leishmaniasis and
mucosal leishmaniasis. The visceral leishmaniasis is based on the reticuloendothelial system
producing hepatomegaly, splenomegaly and lymphadenopathy. In the present article, a semiautomatic
segmentation strategy is proposed to obtain the segmentations of the evolutionary
shapes of visceral leishmaniasis called parasites, specifically of the type amastigote and
promastigote. For this purpose, the optical microscopy images containing said evolutionary
shapes, which are generated from a blood smear, are subjected to a process of transformation
of the color intensity space into a space of intensity in gray levels that facilitate their
subsequent preprocessing and adaptation. In the preprocessing stage, smoothing filters and
edge detectors are used to enhance the optical microscopy images. In a complementary way, a
segmentation technique that groups the pixels corresponding to each one of the parasites,
presents in the considered images, is applied. The results reveal a high correspondence between
the available manual segmentations and the semi-automatic segmentations which are useful for
the characterization of the parasites. The obtained segmentations let us to calculate areas and
perimeters associated with the parasites segmented. These results are very important in clinical
context where both the area and perimeter calculated are vital for monitoring the development
of visceral leishmaniasis
Usefulness of cutting planes in the hierarchical segmentation of cardiac anatomical structures
A spatial geometric plane is defined by the three-dimensional coordinates of a pair of
spatial points and the direction that the normal vector establishes, which is formed by joining
those points by means of an oriented line segment. This type of planes, in three-dimensional
images, is extremely useful as an alternative solution to the problem of low contrast that exhibit
the anatomical structures present in cardiac computed tomography images. To do this, after using
a predetermined filter bank and in order to define a region of interest, a smart operator based on
least squares support vector machines is trained and validated in order to detect the
aforementioned coordinates which enables the location of the plane, in the three-dimensional
space that contains the considered images. Once the structure that is required to segment is
identified, a discriminant function is used that cancels all information not linked to this structure.
In this work, the segmentation of the left ventricle, based on region growing technique, is firstly
considered and then the left atrium is segmented considering region growing technique and an
inverse discriminant function. The results show an excellent correspondence relationship when
the spatial union of both structures is made
Use of computational realistic models for the cardiac ejection fraction calculation
Ejection fraction is one of the most useful clinical descriptors to determine the cardiac
function of a subject. For this reason, obtaining the value of this descriptor is of vital importance
and requires high precision. However, in the clinical routine, to generate the mentioned
descriptor value, a geometric hypothesis is assumed, obtaining an approximate value for this
fraction, usually by excess, and which is a dependent-operator. The aim of the present work is
to propose the accurate calculation of the ejection fraction from realistic models, obtained
computationally, of the cardiac chamber called right ventricle. Normally, the geometric
hypothesis that makes this ventricle coincide with a pyramidal type geometric shape, is not
usually, fulfilled in subjects affected by several cardiac pathologies, so as an alternative to this
problem, the computational segmentation process is used to generate the morphology of the right
ventricle and from it proceeds to obtain, accurately, the ejection fraction value. In this sense, an
automatic strategy based on no-lineal filters, smart operator and region growing technique is
propose in order to generate the right ventricle ejection fraction. The results are promising due
we obtained an excellent correspondence between the manual segmentation and the automatic
one generated by the realistic models
Usefulness of digital images segmentation in pulmonary transplantation
In the presence of pulmonary pathologies such as chronic obstructive pulmonary
disease, diffuse pulmonary disease and cystic fibrosis, among others, it is common to require
the removal or replacement of a portion of lungs. There are several requirements for both
donors and organ receivers (recipients) established in the literature. May be the main one is the
volume that the donor's lungs occupy in the thoracic cavity. This parameter is vital because if
the volume of the lungs exceeds the thoracic cavity of the recipients the transplant, logically, is
unfeasible for physical reasons such as the incompatibility between the receiver lung volume
and the donor lung volume. In this sense, the present paper proposes the creation of a hybrid
technique, based on digital image processing techniques application to raise the quality of the
information related to lungs captured in three-dimensional sequences of computed tomography
and for generating the morphology and the volumes of the lungs, belonging to a patient. During
the filtering stage median, saturated and gradient magnitude filters are applied with the purpose
of addressing the noise and artefacts images problems; whereas during the segmentation stage,
methods based on clustering processes are used to extract the lungs from the images. The
values obtained for the metric that assesses the quality of the hybrid computational technique
reflect its good performance. Additionally, these results are very important in clinical processes
where both the shapes and volumes of lungs are vital for monitoring some lung diseases that
can affect the normal lung physiology
Large cells cancer volumetry in chest computed tomography pulmonary images
Lung cancer is the leading oncological cause of death in the world. As for
carcinomas, they represent between 90% and 95% of lung cancers; among them, non-small cell
lung cancer is the most common type and the large cell carcinoma, the pathology on which this
research focuses, is usually detected with the computed tomography images of the thorax.
These images have three big problems: noise, artifacts and low contrast. The volume of the
large cell carcinoma is obtained from the segmentations of the cancerous tumor generated, in a
semi-automatic way, by a computational strategy based on a combination of algorithms that, in
order to address the aforementioned problems, considers median and gradient magnitude filters
and an unsupervised grouping technique for generating the large cell carcinoma morphology.
The results of high correlation between the semi-automatic segmentations and the manual ones,
drawn up by a pulmonologist, allow us to infer the excellent performance of the proposed
technique. This technique can be useful in the detection and monitoring of large cell carcinoma
and if it is considering this kind of computational strategy, medical specialists can establish the
clinic or surgical actions oriented to address this pulmonary pathology
Effects of new openings on the in/plane behaviour of unreinforced brick masonry walls
Existing brick masonry buildings are frequently modified to satisfy nowadays living
demands. Such modifications may include new windows or doors that connect two rooms and
require openings to be cut from load bearing walls. In current design practice, these interventions are generally designed and verified for vertical load, but the structural behavior of these
altered walls when submitted to in-plane loads (due to seismic actions) is not yet fully understood. Thus, design practice may be inaccurately estimated. The objective of this work is to
evaluate, numerically and experimentally, the effects of introducing openings in masonry solidbrick walls subjected to in-plane loading. Three main parameters are considered for the numerical studies: i) walls dimensions, ii) opening type, iii) opening size. As expected, results
show that walls with medium-large openings are the most vulnerable case-scenario. These numerical results have addressed the design of a representative wall tested at the University of
Brescia. The preliminary results of this experimental program are included in this pape
Experimental and numerical assessment of masonry walls with new openings strengthened with steel frame
The creation of new openings in masonry walls is a frequent intervention executed in existing buildings of
unreinforced masonry composed of clay bricks. These openings are widely seen at the street-level, where spaces are
modified to create new windows or doors for new stores, garages or offices. Depending on their size and position,
these interventions may cause significant decrease of the wall’s original in-plane strength and stiffness, thus,
compromising the building seismic resistance. For example, when several garages are created, one after another, the
risk of inducing the soft-story mechanism, when earthquake forces arrive, increases. Another example is when a door
of significant size is introduced in an originally solid masonry wall, which was a key object to guarantee the box-like
behavior of the structure. The opening would reduce the cross section of the remaining piers and spandrel, and thus,
weaken the wall’s seismic strength. These changes in the original wall have consequences in the box-like behavior,
as during earthquake events, the load demands on the remaining shear walls might be larger than their shear capacity.
Therefore, strengthening techniques must restore as much as possible the loss of stiffness and strength. Besides, for
masonry structures, the technique must be reversible and respect the compatibility between materials, particularly in
the case of protected assets. In an attempt to complying with these requirements, engineering practitioner often
introduce steel profiles forming a frame inside the opening. Steel is usually preferred because of its high level of
reversibility and the stiffness and strength it can provide to masonry without substantially increasing the building
self-weight. The design of this steel frame and the stiffness of the masonry wall with opening is based in the available
analytical tools, i.e., the Timoshenko Beam Theory. From these calculations, the loss of stiffness when passing from
a solid wall to a perforated wall is about 75% for cantilever boundary conditions and 55% for double-fixed. Thus,
very stiff profiles for the steel frame are required. In theory, these profiles are capable of fully restoring the stiffness
and resistance. The present work is dedicated to evaluate the effectiveness of this steel frame technique by means of
experimental and numerical methods. The experimental program was designed to provide full assessment of the
effects of introducing a new door opening in brick masonry walls, from the perforation process to the application of
in-plane cyclic loads . A flexible steel frame was designed using numerical tools and consisted in four profiles welded
together and tied to the surrounding masonry wall by means of dry-driven dowels. The numerical model was validated
against the experimental results, and show that neither a very stiff steel frame nor a more flexible one is capable of
restoring the original solid wall’s stiffness. However, both are capable of restoring the in-plane strength and ductility.
This paper, also shows that using a very stiff profile might lead to a rather brittle response of the reinforced wall, as
the masonry starts cracking before activating the frame. This would not happen with a more flexible profileItalian
Ministry of Education, University, and Research
(MIUR) for her Doctoral Scholarship is gratefully
acknowledged. The Authors also thank the technicians
A. del Barba, A. Botturi from laboratory Pietro Pis
New anisotropic diffusion operator in images filtering
The anisotropic di usion lters have become in the fundamental bases to address
the medical images noise problem. The main attributes of these lters are: the noise removal
e ectiveness and the preservation of the information belonging to the edges that delimit the
objects of an image. Due to these excellent attributes, through this article, a comparative study
is proposed between a new di usion operator and the Lorentz operator, proposed by the pioneers
of anisotropic di usion. For this, a strategy consisting of two phases is designed. In the rst,
called operator construction, the composition of functions is used to generate a new di usion
operator that meets with the conditions reported for this kind of the mathematical object. In the
second phase, denominated ltering, a synthetic cardiac images database, based on computed
tomography, is ltered using the aforementioned operators. According with the value obtained
for the peak of the signal-to-noise ratio, the new operator shows similar performance to the
Lorentz operator. The implementation of this new operator contributes to the generation of
new knowledge in digital image processing context
Left atrial appendage automatic segmentation, in computed tomography images
The left atrial appendage is one of the anatomical places where most frequently
blood thrombi occur. When migrating from the appendage, these thrombi, become blood
emboli that, potentially, can compromise the physiology and/or anatomy of cardiac or cerebral
blood vessels, being able to generate cerebrovascular events. The left atrial appendage
segmentation is very difficult due, mainly, to its location and the identical densitometric
information presents into of this appendage and around of the left atrium. In this paper, an
automatic technique is proposed to segment this appendage with the purpose of generating
important information to the procedure called left atrial appendage surgical closure. This
information is linked to the volume and the diameters of the left atrial appendage. The
technique consists of a digital pre-processing stage, based on filtering processes and definition
of a region of interest and, of one segmentation stage that considers a clustering method. The
results are promising and they allow us to calculate useful quantitative variables when
characterizing the most lethal appendix of the human body represented by the mentioned
appendage. These results are very important in clinical processes where both the shape and
volume of this appendage are vital for detecting and monitoring some vascular diseases such as
cardiac embolism, arterial hypertension and stroke, among others
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