Carlos Leal

Computer-assisted bleeding detection in wireless capsule endoscopy images

Wireless capsule endoscopy (WCE) has revolutionised the diagnosis and treatment of gastrointestinal tract, especially the small intestine where traditional endoscopies cannot reach. However, this new technology leads to the inspection of a large number of images, which is a time-consuming process and also too hard by naked eyes for doctors. In this paper, we propose a new computerised method for bleeding detection in WCE images. We use the second component of CIE Lab colour space together with appropriate segmentation and enhancement techniques, involving an adaptive anisotropic diffusion (alike Perona–Malik diffusion). As a result of this procedure, it is possible to devise four functions to discriminate between bleeding and normal regions in WCE images. These four bleeding detectors rely on the eigenvalues of the Hessian and on the Laplacian of the modified enhanced image. Multiscale image analysis approach is also involved in the definition of these detectors for handling the maximum and minimum sizes at which the bleeding regions are expected to be found. Experimental results on several medical data-sets show that the new algorithm achieves a very good rate of success and promising performance for bleeding detection.

A Generalized Piezoelectric Bernoulli–Navier Anisotropic Rod Model

We apply the asymptotic analysis procedure to the three-dimensional static equations of piezoelectricity, for a linear nonhomogeneous anisotropic thin rod. We prove the weak convergence of the rod mechanical displacement vectors and the rod electric potentials, when the diameter of the rod cross-section tends to zero. This weak limit is the solution of a new piezoelectric anisotropic nonhomogeneous rod model, which is a system of coupled equations, with generalized Bernoulli–Navier equilibrium equations and reduced Maxwell–Gauss equations.

Exploring smartphone sensors for fall detection

Falling, and the fear of falling, is a serious health problem among the elderly. It often results in physical and mental injuries that have the potential to severely reduce their mobility, independence and overall quality of life. Nevertheless, the consequences of a fall can be largely diminished by providing fast assistance. These facts have lead to the development of several automatic fall detection systems. Recently, many researches have focused particularly on smartphone-based applications. In this paper, we study the capacity of smartphone built-in sensors to differentiate fall events from activities of daily living. We explore, in particular, the information provided by the accelerometer, magnetometer and gyroscope sensors. A collection of features is analyzed and the efficiency of different sensor output combinations is tested using experimental data. Based on these results, a new, simple, and reliable algorithm for fall detection is proposed. The proposed method is a threshold-based algorithm and is designed to require a low battery power consumption. The evaluation of the performance of the algorithm in collected data indicates 100 % for sensitivity and 93 % for specificity. Furthermore, evaluation conducted on a public dataset, for comparison with other existing smartphone-based fall detection algorithms, shows the high potential of the proposed method.

A convection-diffusion-shape model for aberrant colonic crypt morphogenesis

It is generally accepted that colorectal cancer is initiated in the small pits, called crypts, that line the colon. Normal crypts exhibit a regular pit pattern, similar in two-dimensions to a U-shape, but aberrant crypts display different patterns, and in some cases show bifurcation. According to several medical articles, there is an interest in correlating pit patterns and the cellular kinetics, namely of proliferative and apoptotic cells, in colonic crypts. This paper proposes and implements a hybrid convection-diffusion-shape model for simulating and predicting what has been validated medically, with respect to some aberrant colonic crypt morphogenesis. The model demonstrates crypt fission, in which a single crypt starts dividing into two crypts, when there is an increase of proliferative cells. The overall model couples the cell movement and proliferation equations with the crypt geometry. It relies on classical continuum transport/mass conservation laws and the changes in the crypt shape are driven by the pressure exerted by the cells on the crypt wall. This pressure is related to the cell velocity by a Darcy-type law. Numerical simulations are conducted and comparisons with the medical results are shown.

Shape Analysis of an Adaptive Elastic Rod Model

We analyze the shape semiderivative of the solution to an asymptotic nonlinear adaptive elastic rod model, derived in Figueiredo and Trabucho [Math. Mech. Solids, 9 (2004), pp. 331--354], with respect to small perturbations of the cross section. The rod model is defined by generalized Bernoulli--Navier elastic equilibrium equations and an ordinary differential equation with respect to time. Taking advantage of the models special structure and the regularity of its solution, we compute and completely identify, in an appropriate functional space involving time, the weak shape semiderivative.

Physiologic Parameter Estimation Using Inverse Problems

The estimation of in vivo physiologic parameters is an important, but difficult, issue in bio-medicine. Therefore the development of mathematical techniques predicting these parameter values is very relevant. In a previous work we have proposed a convection-diffusion-shape model, which correlates colonic crypt patterns with the cellular kinetics occurring inside the crypts (this correlation is significant in the context of colorectal cancer). This model involves several physiologic parameters, for which only qualitative information is available in the literature, such as the birth rate of proliferative cells. In this paper we present a framework for estimating this birth rate parameter, in a colonic crypt, assuming that the distribution of proliferative cells is known in that crypt. More precisely, we resolve an inverse problem, where the unknown coefficient field, the birth rate, is connected to the observed measurements, the proliferative cell density, through a partial differential equation. This inver...

The generalized Goursat-Darboux problem for a third order operator

It is proved that if a generalized Goursat-Darboux problem is C∞well posed then the operator cannot contain derivatives with respect to one of the variables.

Dissimilarity Measure of Consecutive Frames in Wireless Capsule Endoscopy Videos: A Way of Searching for Abnormalities

In a previous work we have shown that the curve representing the dissimilarity measure between consecutive frames of a wireless capsule endoscopic video of the small bowel, obtained by means of an image registration method, can be regarded as a rough indicator of the speed of the capsule, and simultaneously, it is also a valuable auxiliary medical tool. In effect, this curve enables a global and fast interpretation of the video, in the sense that it clearly divides the video frames into two main categories: consecutive frames with similar content, which correspond to low values in the curve, and consecutive frames displaying abrupt changes in the image content, which are depicted by peaks, i.e. high values, in the curve. As the main goal of a wireless capsule video examination consists in searching for abnormal features in the images, the purpose of the present work is to analyse whether this curve can also be used to search, quickly, for abnormalities. The experiments performed focus on bleeding identification in small bowel images.

Smartphone application for emergency signal detection

Currently, a number of studies focus on the study and design of new healthcare technologies to improve elderly health and quality of life. Taking advantage of the popularity, portability, and inherent technology of smartphones, we present an emergency application for smartphones, designated as knock-to-panic (KTP). This innovative and novel system enables users to simply hit their devices in order to send an alarm signal to an emergency service. This application is a complete and autonomous emergency system, and can provide an economic, reliable, and unobtrusive method for elderly monitoring or safety protection. Moreover, the simple and fast activation of KTP makes it a viable and potentially superior alternative to traditional ambient assisted living emergency calls. Furthermore, KTP can be further extended to the general population as well and not just be limited for elderly persons. The proposed method is a threshold-based algorithm and is designed to require a low battery power consumption. The evaluation of the performance of the algorithm in collected data indicates that both sensitivity and specificity are above 90%.

A Multiscale Model for Aberrant Crypt Foci

Computational models of cancer complement the biological study of tumor growth. However, existing modeling approaches can be both inefficient and inaccurate due to the difficulties of representing the complex interactions between cells and tissues. We present a three-dimensional multiscale agent-based model of tumor growth with angiogenesis. The model is designed to easily adapt to various cancer types, although we focus on breast cancer. It includes cellular (genetic control), tissue (cells, blood vessels, angiogenesis), and molecular (VEGF, diffusion) levels of representation. Unlike in most cancer models, both normally functioning tissue cells and tumor cells are included in the model. Tumors grow following the expected spheroid cluster pattern, with growth limited by available oxygen. Angiogenesis, the process by which tumors may encourage new vessel growth for nutrient diffusion, is modeled with a new discrete approach that we propose will decrease computational cost. Our results show that despite proposing these new abstractions, we see similar results to previously accepted angiogenesis models. This may indicate that a more discrete approach should be considered by modelers in the future.