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Publications (97)
The cerebellum is an important structure to determine fetal development because its volume has a high correlation with gestational age. Manual annotation of the cerebellum in 3D ultrasound images (to measure the cerebellar volume) requires highly trained experts to perform a time-consuming task. To assist in this task, we developed a totally automa...
Purpose: To evaluate the performance of discrete compactness and tortuosity in the hippocampi (right and left) as possible magnetic resonance neuroimaging biomarkers to discriminate between populations of controls and subjects with mild cognitive impairment.
Methods: 98 subjects were analyzed, including 49 healthy and 49 with mild cognitive impairm...
Las imágenes de ultrasonido médico ofrecen varias ventajas con respecto a otras modalidades como rayos X, tomografía computarizada y resonancia magnética nuclear. Los equipos de ultrasonido son compactos y el tamaño pequeño de la sonda permite al experto tomar imágenes de una amplia variedad de órganos en 2 y 3 dimensiones. Las principales desventa...
Alzheimer's disease is a multifactorial neurodegenerative disorder preceded by a prodromal stage called mild cognitive impairment (MCI). Early diagnosis of MCI is crucial for delaying the progression and optimizing the treatment. In this study we propose a random forest (RF) classifier to distinguish between MCI and healthy control subjects (HC), i...
Resumen La Enfermedad de Parkinson es uno de los trastornos neurodegenerativos más impac-tantes en la atención a la salud a nivel mundial. En México, el Instituto Nacional de Neurología y Neurocirugía "Manuel Velasco Suárez" reportó, en el año 2018 una prevalen-cia de 50 casos nuevos por cada 100 mil habitantes al año. Evidencia clínica y hallazgos...
3D ultrasound systems have been widely used for fetal brain structures’ analysis. However, the obtained images present several artifacts such as multiplicative noise and acoustic shadows appearing as a function of acquisition angle. The purpose of this research is to merge several partially occluded ultrasound volumes, acquired by placing the trans...
Heart failure is defined as a syndrome characterized by a remodeling in the cardiac muscle structure that diminishes the strength and synchrony of contractions, leading the subject to a functional capacity deterioration that progressively triggers fatal clinical outcomes. There are specific pharmacological therapies to reduce failure progression. H...
Quantification of brain growth is crucial for the assessment of fetal well being, for which ultrasound (US) images are the chosen clinical modality. However, they present artefacts, such as acoustic occlusion, especially after the 18th gestational week, when cranial calcification appears. Fetal US volume registration is useful in one or all of the...
The 3D tortuosity determined in several brain areas is proposed as a new morphological biomarker (BM) to be considered in early detection of Alzheimer's disease (AD). It is measured using the sum of angles method and it has proven to be sensitive to anatomical changes that appear in gray and white matter and temporal and parietal lobes during mild...
Mild cognitive impairment (MCI) is an abnormal deterioration of cognitive functions, whose prevalence is considerable in adults older than 65 years old. Several of these cases will convert to Alzheimer’s disease and therefore, MCI’s simple, proper and opportune diagnosis continues to be a research field with great impact in public health. In this p...
Birth weight (BW) is an important indicator of neonatal well–being associated with multiple adverse conditions and thus its early estimation may be crucial for timely treatment. In this paper we propose a BW estimation strategy based on Support Vector Regression of a set of multimodal maternal–fetal features obtained in pregnancy’s first trimester....
1. Introducción La enfermedad de Alzheimer (EA) es un trastorno neurodegenerativo que conduce a un deterioro de las capacidades cognitivas e intelectuales de forma irreversible, limitando el desempeño de las actividades cotidianas [1]. Esta patología afecta la morfología cerebral, ya sea globalmente o en regiones específicas. Para cuantificar el pr...
Objective
An obsessive-compulsive disorder (OCD) subtype has been associated with streptococcal infections and is called pediatric autoimmune neuropsychiatric disorders associated with streptococci (PANDAS). The neuroanatomical characterization of subjects with this disorder is crucial for the better understanding of its pathophysiology; also, eval...
Symmetry is an important feature in natural and man-made objects; particularly, mirror symmetry is a relevant task in fields such as computer vision and pattern recognition. In the current work, we propose a new method to characterize mirror-symmetry in open and closed curves represented by means of the Slope Chain Code. This representation is inva...
The P300 component of event-related potentials (ERPs) is widely used in the implementation of brain computer interfaces (BCI). In this context, one of the main issues to solve is the binary classification problem that entails differentiating between electroencephalographic (EEG) signals with and without P300. Given the particularly unfavorable sign...
A new method to address the problem of shadowing in fetal brain ultrasound volumes is presented. The proposed approach is based on the spatial composition of multiple 3-D fetal head projections using the weighted Euclidean norm as an operator. A support vector machine, which is trained with optimal textural features, was used to assign weighting ac...
We present a novel approach to describe a P300 by a shape-feature vector, which offers several advantages over the feature vector used by the BCI2000 system. Additionally, we present a calibration algorithm that reduces the dimensionality of the shape-feature vector, the number of trials, and the electrodes needed by a Brain Computer Interface to a...
Emotional processing has an important role in social interaction. We report the findings about the Independent Component Analysis carried out on a fMRI set obtained with a paradigm of face emotional processing. The results showed that an independent component, mainly cerebellar-medial-frontal, had a positive modulation associated with fear processi...
In supplementary material the processes of screening and sample selection, and the results of the second-level anaylisis of the Face Matching Task paradigm are presented.
A computational platform for the simulation, design and analysis of the Polylactic (PLA) acid production process using different lignocellulosic raw materials has been developed. The computational platform considers three main reactive-separation processes: 1) the bio-conversion process, where an hydrolysis-saccharification-culture process to produ...
Ultrasound (US) images of the fetal brain provide the experts with valuable indicators of the fetal development. However as the skull thickens, it obstructs the transmission of the acoustic waves, which in turn occludes the anatomy behind the thickened fetal skull. A viable option to improve the visibility of the fetal brain, before complete calcif...
In this paper we present a fully automatic approach
based on texture maps and optimal ellipse detection to
segment and obtain measurements of the fetal head. The goals
are to segment the fetal head and to measure the biparietal diameter
(BPD) and head circumference (HC) using ultrasound
images. By incorporating texture maps, morphological operation...
We present a discrete compactness (DC) index, together with a classification scheme, based both on the size and shape features extracted from brain volumes, to determine different aging stages: healthy controls (HC), mild cognitive impairment (MCI), and Alzheimer's disease (AD). A set of 30 brain magnetic resonance imaging (MRI) volumes for each gr...
Reported studies describing normal and abnormal aging based on anatomical MRI analysis do not consider morphological brain changes, but only volumetric measures to distinguish among these processes. This work presents a classification scheme, based both on size and shape features extracted from brain volumes, to determine different aging stages: he...
Previous work has shown that the segmentation of anatomical structures on 3D ultrasound data sets provides an important tool for the assessment of the fetal health. In this work, we present an algorithm based on a 3D statistical shape model to segment the fetal cerebellum on 3D ultrasound volumes. This model is adjusted using an ad hoc objective fu...
Radionuclide-based imaging is an alternative to evaluate ventricular function and synchrony and may be used as a tool for the identification of patients that could benefit from cardiac resynchronization therapy (CRT). In a previous work, we used Factor Analysis of Dynamic Structures (FADS) to analyze the contribution and spatial distribution of the...
The brain-computer interfaces (BCI) translate brain activity into commands for a computer. To improve the performance of BCI, it is necessary to improve the feature extraction techniques that are used to decode the intentions of the users and get a clear understanding of the basic conditions for training the classifier. In this paper we study the b...
Brain computer interfaces (BCIs) translate brain activity into computer commands. To enhance the performance of a BCI, it is necessary to improve the feature extraction techniques being applied to decode the users' intentions. Objective comparison methods are needed to analyze different feature extraction techniques. One possibility is to use the c...
Brain computer interfaces (BCIs) translate brain activity into computer commands. To enhance the performance of a BCI, it is necessary to improve the feature extraction techniques being applied to decode the users' intentions. Objective comparison methods are needed to analyze different feature extraction techniques. One possibility is to use the c...
Brain computer interfaces (BCIs) translate brain activity into computer commands. To enhance the performance of a BCI, it is necessary to improve the feature extraction techniques being applied to decode the users' intentions. Objective comparison methods are needed to analyze different feature extraction techniques. One possibility is to use the c...
Objective. - The goal of this research was to design, set up, use and evaluate a realistic simulation platform that could host real-time simulated robotics applications controlled with a brain-computer interface based on an event-related potential paradigm. Materials and methods. - The platform is composed of the following modules: (i) six band-lim...
Factorial phase analysis (FaPI) represents an alternative method to Fourier phase analysis (FoPI) in the evaluation and detection of abnormalities on cardiac contraction patterns, but it has limitations in representing the sequence in abnormal contraction patterns. In this work we propose a modified factorial phase image (FaPIm) that incorporates m...
On March 8, 2008 in Havana, the Latin American Network for Brain Mapping (LABMAN) was created with participants from Argentina, Brazil, Colombia, Cuba and Mexico. The focus of LABMAN is to promote neuroimaging and systems neuroscience in the region through the implementation of training and exchange programs, and to increase public awareness of the...
In this work, a meshless (free Galerkin) method is used to define a realistic head conductor model to solve the EEG inverse problem. The aim is to find sources responsible for scalp potentials with precision and low computation time. In order to assess the proper method's performance, it was evaluated with simulated EEG signals, obtained from diffe...
Magnetic Resonance Imaging (MRI) is increasingly used for the diagnosis and monitoring of neurological disorders. In particular Diffusion-Weighted MRI (DWI) is highly sensitive in detecting early cerebral ischemic changes in acute stroke. Cerebral infarction lesion segmentation from DWI is accomplished in this work by applying nonparametric density...
We present the first results of four projects of a second phase of a Mexican Project Computer Assisted Surgery and Medical Robotics, supported by the Mexican Science and Technology National Council (Consejo Nacional de Ciencia y Tecnología) under grant SALUD-2002-C01-8181. The projects are being developed by three universities (UNAM, UAM, ITESM) an...
Equilibrium radionuclide angiography (ERNA) imaging of the heart is used to visualize and quantify the cardiac function. Phase image analysis has been used for the localization of several conduction and contraction abnormalities and has been proposed to evaluate cardiac resynchronization therapy. The ventricular contraction has been described with...
To delineate arbitrarily shaped clusters in a complex multimodal feature space, such as the brain MRI intensity space, often requires kernel estimation techniques with locally adaptive bandwidths, such as the adaptive mean shift procedure. Proper selection of the kernel bandwidth is a critical step for a better quality in the clustering. This paper...
Brain magnetic resonance imaging segmentation is accomplished in this work by applying nonparametric density estimation, using the mean shift algorithm in the joint spatial-range domain. The quality of the class boundaries is improved by including an edge confidence map, that represents the confidence of truly being in the presence of a border betw...
The evaluation of the upper respiratory airway obstruction is of significant importance, as its physiological effects on ventilation rapidly evolve to secondary body malfunctions. Given the nature and location of the lesions, the invasive handling of the condition with direct bronchoscopy is undesirable; an imaging approach based on computed tomogr...
We introduce a new technique for nonrigid image registration based on the composition of local deformations. The warping model is analyzed in order to guarantee continuity, differentiability and a one-to-one transformation by constraining the parameters of the nonlinear spatial transformation. A genetic algorithm solves the model by global optimiza...
An accurate segmentation of cardiac cavities is necessary to assess cardiac function and to determine quantitative parameters. Several semi-automatic techniques have been tested to achieve this goal. In this work we propose an algorithm to segment cardiac structures, based on a robust pre-processing step that eliminates noise and extracts an initia...
We introduce a new technique for nonrigid registration for medical images based on a hierarchical composition of local deformations. The local deformation model is analyzed in order to guarantee continuity, differentiability and a one-to-one transformation by constraining the parameters of the spatial transformation. The performance of our techniqu...
Segmentation and extraction of cardiac structures from heart images has been of great importance in the quantification of indicative parameters of cardiac pathologies. In this work we propose an algorithm delineate cardiac cavities, based on a robust extraction of the left ventricle, together with a refined deformable model, that integrates edge co...
The most frequently used imaging procedure for the diagnosis of diverse neurological illnesses is magnetic resonance. Improved benefits have been obtained from multi-spectral information under this imaging modality. Both supervised and unsupervised segmentation procedures have been reported for this kind of images, many of which require a preproces...
A voxel-based measure of discrete compactness for brain structures quantification, is presented. The work proposed here simplifies the measure of discrete compactness, which corresponds to the sum of the contact surface areas of the face-connected voxels of the analyzed brain. A relation between the area of the surface enclosing the cerebral volume...
Mild cognitive impairment (MCI) is a borderline condition between normal aging and dementia and is characterized by subjective complains of memory impairments that go beyond those expected considering age and education. Yet subjects are not demented, and their functional status remains intact (Peterson et al. 1999). It is suspected that this group...
In this paper, a nonparametric statistical segmentation procedure based on the computation of the mean shift within the joint space-range feature representation of brain MR images is presented. The mean shift is a simple, nonparametric estimator, which can be implemented in a data-driven approach. The number of classes and other initialization para...
El Deterioro Cognoscitivo Incipiente (DCI) es un estado de transición entre los cambios del funcionamiento mental en el envejecimiento normal y la demencia. Este estado se caracteriza por una pérdida subjetiva de la memoria que no concuerda ni con la edad ni con el nivel educativo de la persona cuyo desempeño de las actividades cotidianas no obstan...
A segmentation procedure using a radial basis function network (RBFN), coupled with an active contour (AC) model based on a cubic splines formulation is presented for the detection of the gray-white matter boundary in axial MMRI (T1, T2 and PD). A RBFN classifier has been previously introduced for MMRI segmentation, with good generalization at a ra...
The segmentation of cerebral MRI is approached as a classification problem where the density function is unknown. For MR images, the modes of the intensity distribution are related to cluster centers obtained from anatomical structures of brain images. The modes of the unknown density function can be calculated by applying the mean-shift method. Th...
This article compares results obtained in previous studies using time-frequency representations (Wigner-Ville, Choi-Williams and Parametric) and the wavelet transform with those obtained with wavelet packet functions to show new findings about their quality in the analysis of ECoG recordings in human intractable epilepsy: data from 21 patients have...
Spatial quantification of relevant brain structures, is usually carried out through the analysis of a stack of magnetic resonance (MR) images by means of some image segmentation approach. In this paper, multispectral MR imaging segmentation based on a modified radial-basis function network is presented. Multispectral MR image sets are constructed b...
A fully automatic method to deform medical images is proposed. The procedure is based on the application of a set of consecutive local linear transformations at fixed landmarks, generating a global non-linear deformation. Continuity is guaranteed by a smooth change form the landmark point to the neighborhood, which is a homotopy between an affine t...
RESUMEN En este trabajo se presenta la evaluación de un sistema que proporciona acceso a un programa de mapeo cerebral tridimensional para cuaquier usuario remoto. El cliente puede cargar sus señales cerebrales, ya sea electroencefalograma o potencial evocado y desplegar los mapas 3D en su máquina local. El mapa 3D se construye remotamente por el s...
Spatial quantification of relevant brain structures, is usually carried out through the analysis of a stack of magnetic resonance (MR) images by means of some image segmentation approach. In this paper, multispectral MR imaging segmentation based on a modified radial-basis function network is presented. Multispectral MR image sets are constructed b...
This study examines the effect of static and dynamic leg exercises on heart rate variability (HRV) and blood pressure variability (BPV) in humans.
10 healthy male subjects were studied at rest, during static exercise performed at 30% of maximal voluntary contraction (SX30), and during dynamic cycling exercises done at 30% of VO2max (DX30) and at 60...
We present an analysis of the heart rate variability during the Valsalva manoeuvre. The more frequently used time-frequency distributions were applied in order to analyse the dynamical behaviour of several spectral indexes during the manoeuvre. The influence of the branches of the autonomous system can be predicted following the evolution of the st...
Tracheal stenosis is an uncommon pathology that in early stages is
often confused with different respiratory affections by its signs and
symptoms. An automatic characterization of the tracheal stenosis
requires adequate medical images and efficient segmentation algorithms.
In CT images, several algorithms of airway segmentation have been used,
such...
Segmentation of cardiac structures has a great impact in the
quantification of parameters indicative of heart function. The preferred
technique for this segmentation is based on edge detection, where
deformable models have extensively been used to obtain cardiac cavities
contours. This work proposes two alternatives to the traditionally used
active...
Robust high-breakdown-point location estimators are employed to analyze image stacks under the piecewise constant image structure model. To reduce the effect of bias along the Z-axis, the class parameters are extracted using three consecutive slices, The segmentation algorithm first determines the most reliable seed regions, which are then used in...
Two fully automatic restoration-segmentation algorithms are
proposed for the processing of biased magnetic resonance images. A first
approach is based on an expectation-maximization procedure, where the
initial conditions for the class distribution parameters and the number
of classes are obtained, without any a priori knowledge, from a
mode-based...
The authors recently presented a procedure for the processing of
abdominal ECG signals. Here, they expose an intensive evaluation of the
procedure, in a comprehensive set of simulated and real signals, which
allow them to report its dynamic range of operation concerning the noise
level and the fetal and maternal QRS amplitude. Although the procedur...
Four temporal and four spectral parameters of heart rate variability were compared after they were computed with two different time series generation methods: the RR intervals and the numerical values of heart rate provided by the Finapres. Recordings were obtained from 10 healthy subjects throughout five experimental conditions: supine, standing,...
Robust high breakdown point location estimators are employed to analyze image stacks under the piecewise constant image structure model. To reduce the effect of bias along the Z axis, the class parameters are extracted using three consecutive slices. The segmentation algorithm first determines the most reliable seed regions which are then used in a...
Anatomic and functional atlases are very useful tools in
stereotactic neurosurgery planning. This work presents a first
approximation to the construction of an anatomical human brain atlas,
which can be considered as a representative model of the local
population. The atlas is built up from MRI stacks, obtained with a 1.5 T
imager which is able to...
The power spectral analysis of the beat to beat variations in
parameters related to the ventricular performance may provide
information concerning the autonomic control of the mechanical function
of the heart. The peak of the first derivative of the ear densitogram
(PD) has been used as a noninvasive index to evaluate the left
ventricular function....
Two parameters to measure propofol's sedation effect on the EEG
signal are presented. One parameter is based on a wavelet
multiresolution decomposition that allows spectral analysis on each
detail. The other parameter is based on cross spectrum analysis that
underlines similar frequency phenomena that appear in two different EEG
epochs. Both parame...
A modular approach for extracting 3D information from a stack of
2D slices is presented. The bottom-up procedure makes extensive use of
robust high breakdown point estimators adapted to image analysis. All
the decision parameters are either derived from the data or are
context-independent. A priori information is easy to integrate, and the
reliabil...
Statistical mapping is widely used in electrophysiological research. T-statistic mapping is commonly used in between-group map comparison. The t-map, which is based upon the equal variance of groups, was the first type of statistical mapping to be used in this field. Later, a t-map, and a p-map using the unequal variance hypothesis were introduced....
A high precision method for fetal QRS complex extraction from the
abdominal ECG is presented. The method is based on a wavelet
multiresolution decomposition and a pattern matching procedure. The
wavelet analysis allowed the elimination of detail signals that did not
have maternal and fetal QRS frequency components and it also allowed
maternal and f...
The purpose of the present paper was to introduce a new kind of brain mapping displaying significance probability level associated to Fisher's test. The latter measures the degree of difference between variances of two groups. This map can be considered as complementary to that representing the between-group mean differences. The interpretation of...
The determination of the position and extension of several brain tumors is made with the help of a two dimensional (2D) and a three dimensional (3D) brain electrical activity mapping systems. A comparison of these two determination is carried out and correlated with the exact position of the lesion determined with the help of anatomical data. We sh...