23 research outputs found
Advancements and Breakthroughs in Ultrasound Imaging
Ultrasonic imaging is a powerful diagnostic tool available to medical practitioners, engineers and researchers today. Due to the relative safety, and the non-invasive nature, ultrasonic imaging has become one of the most rapidly advancing technologies. These rapid advances are directly related to the parallel advancements in electronics, computing, and transducer technology together with sophisticated signal processing techniques. This book focuses on state of the art developments in ultrasonic imaging applications and underlying technologies presented by leading practitioners and researchers from many parts of the world
Fusion of magnetic resonance and ultrasound images for endometriosis detection
Endometriosis is a gynecologic disorder that typically affects women in their reproductive age and is associated with chronic pelvic pain and infertility. In the context of pre-operative diagnosis and guided surgery, endometriosis is a typical example of pathology that requires the use of both magnetic resonance (MR) and ultrasound (US) modalities. These modalities are used side by sidebecause they contain complementary information. However, MRI and US images have different spatial resolutions, fields of view and contrasts and are corrupted by different kinds of noise, which results in important challenges related to their analysis by radiologists. The fusion of MR and US images is a way of facilitating the task of medical experts and improve the pre-operative diagnosis and the surgery mapping. The object of this PhD thesis is to propose a new automatic fusion method for MRI and US images. First, we assume that the MR and US images to be fused are aligned, i.e., there is no geometric distortion between these images. We propose a fusion method for MR and US images, which aims at combining the advantages of each modality, i.e., good contrast and signal to noise ratio for the MR image and good spatial resolution for the US image. The proposed algorithm is based on an inverse problem, performing a super-resolution of the MR image and a denoising of the US image. A polynomial function is introduced to modelthe relationships between the gray levels of the MR and US images. However, the proposed fusion method is very sensitive to registration errors. Thus, in a second step, we introduce a joint fusion and registration method for MR and US images. Registration is a complicated task in practical applications. The proposed MR/US image fusion performs jointly super-resolution of the MR image and despeckling of the US image, and is able to automatically account for registration errors. A polynomial function is used to link ultrasound and MR images in the fusion process while an appropriate similarity measure is introduced to handle the registration problem. The proposed registration is based on a non-rigid transformation containing a local elastic B-spline model and a global affine transformation. The fusion and registration operations are performed alternatively simplifying the underlying optimization problem. The interest of the joint fusion and registration is analyzed using synthetic and experimental phantom images
Upper airways segmentation using principal curvatures
Esta tesis propone una nueva técnica para segmentar las vías aéreas superiores. Esta propuesta
permite la extracción de estructuras curvilíneas usando curvaturas principales. La propuesta
permite la extracción de éstas estructuras en imágenes 2D y 3D. Entre las principales novedades
se encuentra la propuesta de un nuevo criterio de parada en la propagación del algoritmo de
realce de contraste (operador multi-escala de tipo sombrero alto). De la misma forma, el criterio
de parada propuesto es usado para detener los algoritmos de difusión anisotrópica. Además, un
nuevo criterio es propuesto para seleccionar las curvaturas principales que conforman las
estructuras curvilíneas, que se basa en los criterios propuestos por Steger, Deng et. al. y
Armande et. al. Además, se propone un nuevo algoritmo para realizar la supresión de nomáximos
que permite reducir la presencia de discontinuidades en el borde de las estructuras
curvilíneas. Para extraer los bordes de las estructuras curvilíneas, se utiliza un algoritmo de
enlace que incluye un nuevo criterio de distancia para reducir la aparición de agujeros en la
estructura final. Finalmente, con base en los resultados obtenidos, se utiliza un algoritmo
morfológico para cerrar los agujeros y se aplica un algoritmo de crecimiento de regiones para
obtener la segmentación final de las vías respiratorias superiores.This dissertation proposes a new approach to segment the upper airways. This proposal allows
the extraction of curvilinear structures based on the principal curvatures. The proposal
allows extracting these structures from 2D and 3D images. Among the main novelties is the
proposal of a new stopping criterion to stop the propagation of the contrast enhancement algorithm
(multiscale top-hat morphological operator). In the same way, the proposed stopping
criterion is used to stop the anisotropic diffusion algorithms. In addition, a new criterion is
proposed to select the principal curvatures that make up the curvilinear structures, which is
based on the criteria proposed by Steger, Deng et. al. and Armande et. al. Furthermore, a
new algorithm to perform the non-maximum suppression that allows reducing the presence
of discontinuities in the border of curvilinear structures is proposed. To extract the edges of
the curvilinear structures, a linking algorithm is used that includes a new distance criterion to
reduce the appearance of gaps in the final structure. Finally, based on the obtained results, a
morphological algorithm is used to close the gaps and a region growing algorithm to obtain
the final upper airways segmentation is applied.Doctor en IngenieríaDoctorad
Variational methods and its applications to computer vision
Many computer vision applications such as image segmentation can be formulated in a ''variational'' way as energy minimization problems. Unfortunately, the computational task of minimizing these energies is usually difficult as it generally involves non convex functions in a space with thousands of dimensions and often the associated combinatorial problems are NP-hard to solve. Furthermore, they are ill-posed inverse problems and therefore are extremely sensitive to perturbations (e.g. noise). For this reason in order to compute a physically reliable approximation from given noisy data, it is necessary to incorporate into the mathematical model appropriate regularizations that require complex computations.
The main aim of this work is to describe variational segmentation methods that are particularly effective for curvilinear structures. Due to their complex geometry, classical regularization techniques cannot be adopted because they lead to the loss of most of low contrasted details. In contrast, the proposed method not only better preserves curvilinear structures, but also reconnects some parts that may have been disconnected by noise. Moreover, it can be easily extensible to graphs and successfully applied to different types of data such as medical imagery (i.e. vessels, hearth coronaries etc), material samples (i.e. concrete) and satellite signals (i.e. streets, rivers etc.). In particular, we will show results and performances about an implementation targeting new generation of High Performance Computing (HPC) architectures where different types of coprocessors cooperate. The involved dataset consists of approximately 200 images of cracks, captured in three different tunnels by a robotic machine designed for the European ROBO-SPECT project.Open Acces
Advanced Sensing and Image Processing Techniques for Healthcare Applications
This Special Issue aims to attract the latest research and findings in the design, development and experimentation of healthcare-related technologies. This includes, but is not limited to, using novel sensing, imaging, data processing, machine learning, and artificially intelligent devices and algorithms to assist/monitor the elderly, patients, and the disabled population
Characterising pattern asymmetry in pigmented skin lesions
Abstract. In clinical diagnosis of pigmented skin lesions asymmetric pigmentation is often indicative of
melanoma. This paper describes a method and measures for characterizing lesion symmetry. The estimate of
mirror symmetry is computed first for a number of axes at different degrees of rotation with respect to the
lesion centre. The statistics of these estimates are the used to assess the overall symmetry. The method is
applied to three different lesion representations showing the overall pigmentation, the pigmentation pattern,
and the pattern of dermal melanin. The best measure is a 100% sensitive and 96% specific indicator of
melanoma on a test set of 33 lesions, with a separate training set consisting of 66 lesions
MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications
Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described