2D-3D Rigid-Body Registration of X-Ray Fluoroscopy and CT Images

The registration of pre-operative volumetric datasets to intra- operative two-dimensional images provides an improved way of verifying patient position and medical instrument loca- tion. In applications from orthopedics to neurosurgery, it has a great value in maintaining up-to-date information about changes due to intervention. We propose a mutual information- based registration algorithm to establish the proper align- ment. For optimization purposes, we compare the perfor- mance of the non-gradient Powell method and two slightly di erent versions of a stochastic gradient ascent strategy: one using a sparsely sampled histogramming approach and the other Parzen windowing to carry out probability density approximation. Our main contribution lies in adopting the stochastic ap- proximation scheme successfully applied in 3D-3D registra- tion problems to the 2D-3D scenario, which obviates the need for the generation of full DRRs at each iteration of pose op- timization. This facilitates a considerable savings in compu- tation expense. We also introduce a new probability density estimator for image intensities via sparse histogramming, de- rive gradient estimates for the density measures required by the maximization procedure and introduce the framework for a multiresolution strategy to the problem. Registration results are presented on uoroscopy and CT datasets of a plastic pelvis and a real skull, and on a high-resolution CT- derived simulated dataset of a real skull, a plastic skull, a plastic pelvis and a plastic lumbar spine segment.

A Statistical Image-Based Shape Model for Visual Hull Reconstruction and 3D Structure Inference

We present a statistical image-based shape + structure model for Bayesian visual hull reconstruction and 3D structure inference. The 3D shape of a class of objects is represented by sets of contours from silhouette views simultaneously observed from multiple calibrated cameras. Bayesian reconstructions of new shapes are then estimated using a prior density constructed with a mixture model and probabilistic principal components analysis. We show how the use of a class-specific prior in a visual hull reconstruction can reduce the effect of segmentation errors from the silhouette extraction process. The proposed method is applied to a data set of pedestrian images, and improvements in the approximate 3D models under various noise conditions are shown. We further augment the shape model to incorporate structural features of interest; unknown structural parameters for a novel set of contours are then inferred via the Bayesian reconstruction process. Model matching and parameter inference are done entirely in the image domain and require no explicit 3D construction. Our shape model enables accurate estimation of structure despite segmentation errors or missing views in the input silhouettes, and works even with only a single input view. Using a data set of thousands of pedestrian images generated from a synthetic model, we can accurately infer the 3D locations of 19 joints on the body based on observed silhouette contours from real images.

Media influences on body satisfaction in female students. 'Influencia de la publicidad en la satisfacci??n corporal de estudiantes universitarios'

Resumen tomado de la publicaci??n

A concurrent region growing algorithm guided by circumscribed contours

Image segmentation of natural scenes constitutes a major problem in machine vision. This paper presents a new proposal for the image segmentation problem which has been based on the integration of edge and region information. This approach begins by detecting the main contours of the scene which are later used to guide a concurrent set of growing processes. A previous analysis of the seed pixels permits adjustment of the homogeneity criterion to the region's characteristics during the growing process. Since the high variability of regions representing outdoor scenes makes the classical homogeneity criteria useless, a new homogeneity criterion based on clustering analysis and convex hull construction is proposed. Experimental results have proven the reliability of the proposed approach

A new approach to segmentation based on fusing circumscribed contours, region growing and clustering

One of the major problems in machine vision is the segmentation of images of natural scenes. This paper presents a new proposal for the image segmentation problem which has been based on the integration of edge and region information. The main contours of the scene are detected and used to guide the posterior region growing process. The algorithm places a number of seeds at both sides of a contour allowing stating a set of concurrent growing processes. A previous analysis of the seeds permits to adjust the homogeneity criterion to the regions's characteristics. A new homogeneity criterion based on clustering analysis and convex hull construction is proposed

The Human Body

A set of images which can be used within the University for teaching students.

body scan exercise

This exercise is a mojor part of a recognised mindfulness programme and has been included in the faculty staff wellness at work project. The recording takes 20 - 25 mins to listen to.

Body mass index as a standard of living measure: a different interpretation for the case of Colombia

We analyze the Body Mass Index (BMI) in a distinct way of its traditional use and it lets us use it as a proxy of standard of living for the case of Colombia. Our approach is focused on studying how far the people are from the normal range and not on the score of each one and this lets us to treat equally extreme cases as severe thinness and obesity. We use a probabilistic model (Ordered Probit) that evaluates the probability of being within the normal range or another level. We found that socioeconomic variables have a significant effect on the dependent variable and that there are no linear effects. Besides, people with difficulties for walking and adults have less probability of having a normal BMI.

The human body.

Se presenta un objeto digital educativo pensado para alumnos de quinto curso de Primaria con el que conocerán, en inglés, las distintas partes de cuerpo humano, los cinco sentidos y a qué parte del cuerpo se asocian.

The main contours of Richard S. Peters's concept of moral education.

Exponer de modo sistemático las ideas que la autora considera imprescindibles para comprender el concepto de la educación moral de Richard Stanley Peters . En el primer capítulo se ofrece el perfil de Peters y una visión general sobre la educación moral y sus obras. Los tres capítulos siguientes presentan 'el mapa' de su pensamiento. Concretamente, la exposición se desarrolla en torno a cuatro aspectos o utilizando la terminología de Peters, se refiere a estos aspectos como 'signposts'. El capítulo segundo está dedicado a la finalidad de la educación moral y el tercero al educando y su desarrollo. Los otros dos aspectos, -el contenido y los procesos, están tratados en el capítulo cuatro. Al final de la exposición y a modo de conclusión, la autora ofrece algunas valoraciones de las contribuciones de Peters. Una síntesis de las conclusiones se puede expresar en la siguiente fórmula: los aspectos que Peters cuestiona respecto a algunos planteamientos más influenciados por Kant tienen validez. Sin embargo, la solución que propone se puede decir que queda a 'mitad del camino' porque al final, Peters no consiguió superar del todo los reduccionismos que caracterizan los puntos de vista que él pretendió armonizar. Este fracaso está vinculado al método de la filosofía analítica.