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A three-dimensional anatomically and electro-physiologically realistic model of atrial propagation is developed utilizing generic cardiac ionic models fitted to experimentally recorded action potentials (APs). The atrial geometry incorporated realistic wall thickness and twelve anatomical structures, including the sino-atrial node (SAN), pulmonary veins, interatrial septum, Bachmann's bundle and coronary...
Electroconvulsive therapy (ECT) is the most effective treatment for severe depressive disorder, and yet the mechanisms of its therapeutic effects remain largely unknown. A novel computational model is presented in this study to simulate and investigate direct cortical excitation caused by bitemporal electroconvulsive therapy (BT ECT), using a finite element model (FEM) of the human head. The skull...
Left ventricular hypertrophy (LVH) is a complex cardiac condition mainly identified by the thickening of the myocardial wall. Although most of the contemporary cardiac imaging modalities provide high resolution 3D images, the wall thickness (WT) is still measured within the acquired planes. This way of measurement may introduce an error as cardiac wall is not necessarily orthogonal to the plane. In...
In this paper, a fully automated method for segmenting Left Ventricle (LV) in echocardiography images is proposed. A new method named active ellipse model is developed to automatically find the best ellipse inside the LV chamber without intervention of any specialist. A modified B-Spline Snake algorithm is used to segment the LV chamber in which the initial contour is formed by the predefined ellipse...
Automatic pectoral muscle removal on medio-lateral oblique view of mammogram is an essential step for many mammographic processing algorithms. However, the wide variability in the position of the muscle contour, together with the similarity between in muscle and breast tissues makes the detection a difficult task. In this paper, we propose a two step procedure to detect the muscle contour. In a first...
The finite difference time domain (FDTD) method is a popular technique for computational electromagnetics (CEM). The large computational power often required, however, has been a limiting factor for its applications. In this paper, we will present a graphics processing unit (GPU)-based parallel FDTD solver and its successful application to the investigation of a novel B1 shimming scheme for high-field...
Phase unwrapping is a classical problem in Magnetic Resonance Imaging (MRI), Interferometric Synthetic Aperture Radar and Sonar (InSAR/InSAS), fringe pattern analysis, and spectroscopy. Although many methods have been proposed to address this problem, robust and effective phase unwrapping remains a challenge. This paper presents a novel phase unwrapping method using a region-based Markov Random Field...
Cranioplasty is a commonly performed procedure. Outcomes can be improved by the use of patient specific implants, however, high costs limit their accessibility. This paper presents a low cost alternative technique to create patient specific polymethylmethacrylate (PMMA) implants using rapid prototyped mold template. We used available patient's CT-scans, one dataset without craniotomy and one with...
A novel approach is proposed for generating data driven models of the lung nodules appearing in low dose CT (LDCT) scans of the human chest. Four types of common lung nodules are analyzed using Active Appearance Model methods to create descriptive lung nodule models. The proposed approach is also applicable for automatic classification of nodules into pathologies given a descriptive database. This...
Atherosclerotic plaques form at specific sites of the arterial tree, an observation that has led to the "geometric risk factor" hypothesis for atherogenesis. It is accepted that the location of atherosclerotic plaques is correlated with sites subjected to low abnormal values of wall shear stress (WSS), which is in turn determined by the specific geometry of the arterial segment. In particular,...
The geometry of conduits derived from in vivo image data is subject to acquisition and reconstruction errors. This results in a degree of uncertainty in defining the bounding geometry for a patient-specific anatomical conduit. The impact of the conduit geometry uncertainty should be considered with respect to haemodynamic clinically relevant measures that may alter the perception and evaluation of...
In this paper, we develop methodology to locate cephalometric landmarks on X-ray images based on probabilistic relaxation, which combines local contextual information from the general shape of the bones of the head (used as measurements specific to each landmark in the form of its shape context) and relational information, expressing the relative position of the landmarks with respect to each other.
Accurate three-dimensional (3D) models of lumbar vertebrae can enable image-based 3D kinematic analysis. The common approach to derive 3D models is by direct segmentation of CT or MRI datasets. However, these have the disadvantages that they are expensive, time-consuming and/or induce high-radiation doses to the patient. In this paper, we present a technique to reconstruct a scaled 3D lumbar vertebral...
Computation of functional regional scores requires proper identification of LV contours. On one hand, manual segmentation is robust, but it is time consuming and requires high expertise. On the other hand, the tag pattern in TMR sequences is a problem for automatic segmentation of LV boundaries. We propose a segmentation method based on a predictor-corrector (Active Contours - Shape Models) scheme...
Using an interactive, 3D, kinematic simulation of the human skeleton, the motion of the sacro-iliac (SI) joint is modeled based upon descriptions available in the literature. The major ligaments are added to the simulation data structure using deformable cubic B-spline curve paths. Ligament strains were generated and studied in response to the motion simulations. Results improve our understanding...
In this paper, we present an algorithm for automatic liver segmentation from CT scans which is based on a statistical shape model. The proposed method is a hybrid method that combines three steps: 1) Localization of the average liver shape model in a test CT volume via 3D generalized Hough transform; 2) Subspace initialization of the statistical shape model; 3) Deformation of the shape model to adapt...
Motivation: Needle-based biopsy and local therapy of prostate cancer depend multimodal imaging for both target planning and needle guidance. The clinical process involves selection of target locations in a pre-operative image volume and registering these to an intra-operative volume. Registration inaccuracies inevitably lead to targeting error, a major clinical concern. The analysis of targeting error...
This paper is concerned with the classification of tumoral tissue in the small bowel by using capsule endoscopic images. The followed approach is based on texture classification. Texture descriptors are derived from selected scales of the Discrete Curvelet Transform (DCT). The goal is to take advantage of the high directional sensitivity of the DCT (16 directions) when compared with the Discrete Wavelet...
Realistic models of the muscle fibers in the myocardium improve the understanding and simulation of the bio-mechanical behavior of the heart. Since Diffusion Tensor Imaging (DTI) allows to visualize the fiber structures in the tissues, this modality can be used to build fiber models. In this paper, we propose an automatic method for the analysis of the helix and transverse angles between the fibers...
Statistical shape models (SSMs) have been used widely as a basis for segmenting and interpreting complex anatomical structures. The robustness of these models are sensitive to the registration procedures, i.e., establishment of a dense correspondence across a training data set. In this work, two SSMs based on the same training data set of scoliotic vertebrae, and registration procedures were compared...
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