In this work, our goal is to track visual targets using residual vector quantization (RVQ). We compare our results with principal components analysis (PCA) and tree structured vector quantization (TSVQ) based tracking. This work is significant since PCA is commonly used in the Pattern Recognition, Machine Learning and Computer Vision communities. On the other hand, TSVQ is commonly used in the Signal Processing and data compression communities. RVQ with more than two stages has not received much attention due to the difficulty in producing stable designs. In this work, we bring together these different approaches into an integrated tracking framework and show that RVQ tracking performs best according to multiple criteria on publicly available datasets. Moreover, an advantage of our approach is a learning-based tracker that builds the target model while it tracks, thus avoiding the costly step of building target models prior to tracking.

This research centers on the fabrication, characterization, and engineering of inverse opal scaffolds, a novel class of three-dimensional (3D) porous scaffolds made of biocompatible and biodegradable polymers, for applications in tissue engineering and regenerative medicine. The unique features of an inverse opal scaffold include a highly ordered array of pores, uniform and finely tunable pore sizes, high interconnectivity, and great reproducibility. The first part of this work focuses on the fabrication and functionalization of inverse opal scaffolds based on poly(D,L-lactic-co-glycolic acid) (PLGA), a biodegradable material approved by the U.S. Food and Drug Administration (FDA). The advantages of the PLGA inverse opal scaffolds are also demonstrated by comparing with their counterparts with spherical but non-uniform pores and poor interconnectivity. The second part of this work shows two examples where the PLGA inverse opal scaffolds were successfully used as a well-defined system to investigate the effect of pore size of a 3D porous scaffold on the behavior of cell and tissue growth. Specifically, I have demonstrated that i) the differentiation of progenitor cells in vitro was dependent on the pore size of PLGA-based scaffolds and the behavior of the cells was determined by the size of individual pores where the cells resided in, and ii) the neovascularization process in vivo could be directly manipulated by controlling a combination of pore and window sizes when they were applied to a mouse model. The last part of this work deals with the novel application of photoacoustic microscopy (PAM), a volumetric imaging modality recently developed, to tissue engineering and regenerative medicine, in the context of non-invasive imaging and quantification of cells and tissues grown in PLGA inverse opal scaffolds, both in vitro and in vivo. Furthermore, the capability of PAM to monitor and quantitatively analyze the degradation of the scaffolds themselves was also demonstrated.

We propose a new approach for defining mechanical properties of the brain tissue in-vivo by taking MRI or CT images of a brain response to ventriculostomy operation, i.e., the relief of the elevated pressure in the ventricular cavities. Then, based on 3-D image analysis, the displacement fields are recovered from these images. Constitutive parameters of the brain tissue are determined using inverse analysis and a numerical method allowing for computations of large strain deformations. We tested this approach in controlled laboratory experiments with silicone brain models mimicking brain geometry, mechanical properties, and boundary conditions. The ventriculostomy was simulated by inflating and deflating internal cavities that model cerebral ventricles. Subsequently, the silicone brain model was described by a hyperelastic (neo-Hookean) material. The obtained mechanical properties have been verified with direct laboratory tests. Properties of real brain tissue are more complicated, but the proposed approach requires only conventional medical images collected before and after ventriculostomy. Breast cancer is the second most prevalent cancer in women, and an operative mastectomy is frequently a part of the treatment. Women often choose to follow a mastectomy with a reconstruction surgery using a breast implant. Furthermore, there is a growing demand for breast augmentation for the sake of aesthetic improvement. In this dissertation, we also developed a quantitative large-strain 3-D mechanical model of female breast deformation. The results show that the stiffness of skin and the constitutive parameters of the breast tissue are important factors affecting breast shape. Our results also suggest that the published Mooney-Rivlin parameters of breast tissue are underestimated by at least one or two orders of magnitude. Scale analysis, representing female breast as a cantilever beam, confirms these conclusions. Subdural hematoma (tearing and bleeding between scull and brain) is one of the major complications of the ventriculostomy operations. Understanding the mechanism of subdural hematoma is critically important for development of more effective medical treatments. In this work, we developed a simple, spherically-symmetrical poroelastic model of the ventriculostomy operation and studied brain response to the pressure change in the ventricles. The observed effect of the material properties on the occurrence of subdural hematoma may be useful for making clinical decisions.

The study of myocardial motion is essential for understanding the normal heart function and developing new treatments for cardiovascular diseases. The goals of my PhD research is to develop new methods for cardiac deformation recovery from 3D magnetic resonance (MR) images. The main contribution of my work is that the proposed methods are guaranteed to generate exactly or nearly incompressible deformations. This is a desirable property since the myocardium has been shown to be close to incompressible. From the recovered deformation, one can directly compute a number of clinically useful parameters, including strains. The first method for 3D deformation recovery of the left ventricular wall (LV) from anatomical cine MRI is based on a deformable model that is incompressible. This method is not suitable for the deformation recovery of the biventricular wall. The second method is based on a 3D deformable model that is nearly incompressible. The model uses a matrix-valued radial basis function to represent divergence free displacement fields, which is a first order approximation of incompressibility. This representation allows for deformation modeling of arbitrary topologies with a relatively small number of parameters, which is suitable for representing the motion of the multi-chamber structure of the heart. The two methods have similar performance. A method to obtain a smooth and accurate surface of the myocardium wall is needed to illustrate the cardiac deformation recovery. I present a novel method for the generation of endocardial and epicardial surface meshes. The same algorithm is independently used to generate the surface meshes of the epicardium and endocardium of the four cardiac chambers. It provides smooth meshes despite the strong voxel anisotropy, which is not the case for the marching cubes algorithm. Phase velocity MRI is an acquisition technique that contains more information about the myocardial motion than cine MRI. I present a method to interpolate the velocity vector field in a phase velocity MRI sequence. The method uses an interpolation model that provides a continuous divergence free velocity vector field, which means that the corresponding deformation is incompressible.

The photoconductive method is one of the oldest methods for the generation of THz room temperature operated THz electromagnetic waves. The THz photoconductive source has operated at a lower power level in the order of hundreds of nW. In addition, the energy conversion of optical to THz efficiency has remained extremely low. One of the most efficient THz photoconductive sources is a trap-enhanced field (TEF) effect source. The field is measured to contain more than 90% of the total DC bias within the first 5 µm of an 80 µm gap between the electrodes reaching kV/cm with only a modest bias. The overall THz power, however, has remained low, due to its rapid saturation. To date, there has been a limited understanding of the TEF effect. In this thesis, a more detailed experimental investigation of TEF effect current transport and field distribution based on annealing is presented to explain some of the underlining physics of TEF effect. A spatially extended line excitation is introduced to effectively reduce the screening effect while still exploiting the TEF region to maintain high efficiency and reach the µW regime. The record efficiency reached by this method is demonstrated. An experimental demonstration with a numerical analysis of the line excitation is presented. The spectral analysis of both a point and a line excitation demonstrate that the line excitation spectrum is not only comparable to that of the point excitation, but also extends the range of useful lower frequency content. To further improve the THz efficiency, the line excitation THz array is investigated.

With the advance of the LCD technology, video quality is becoming increasingly important. In this thesis, we develop hardware-friendly low-complexity enhancement algorithms. Video quality enhancement methods can be classified into two main categories. Single frame methods are the first category. These methods have generally low computational complexity. Multi-frame methods combine information from more than one frame and require the motion information of objects in the scene to do so. We first concentrate on the contrast-enhancement problem by using both global (frame-wise) and local information derived from the image. We use the image histogram and present a regularization-based histogram modification method to avoid problems that are often created by histogram equalization. Next, we design a compression artifact reduction algorithm that reduces ringing artifacts, which is disturbing especially on large displays. Furthermore, to remove the blurriness in the original video we present a non-iterative diffusion-based sharpening algorithm, which enhances edges in a ringing-aware fashion. The diffusion-based technique works on gradient approximations in a neighborhood individually. This gives more freedom compared to modulating the high-pass filter output that is used to sharpen the edges. Motion estimation enables applications such as motion-compensated noise reduction, frame-rate conversion, de-interlacing, compression, and super-resolution. Motion estimation is an ill-posed problem and therefore requires the use of prior knowledge on motion of objects. Objects have inertia and are usually larger then pixels or a block of pixels in size, which creates spatio-temporal correlation. We design a method that uses temporal redundancy to improve motion-vector search by choosing bias vectors from the previous frame and adaptively penalizes deviations from the bias vectors. This increases the robustness of the motion-vector search. The spatial correlation is more reliable because temporal correlation is difficult to use when the objects move fast or accelerate in time, or have small sizes. Spatial smoothness is not valid across motion boundaries. We investigate using energy minimization for motion estimation and incorporate the spatial smoothness prior into the energy. By formulating the energy minimization iterations for each motion vector as the primal problem, we show that the dual problem is motion segmentation for that specific motion vector.

[Truncated abstract] In this thesis, we introduce a mammogram analysis system developed for the automatic segmentation and analysis of mammograms. This original system has been designed to aid radiologists to detect breast cancer on mammograms. The system embodies attribute-driven segmentation in which the attributes of an image are extracted progressively in a step-by-step, hierarchical fashion. Global, low-level attributes obtained in the early stages are used to derive local, high-level attributes in later stages, leading to increasing refinement and accuracy in image segmentation and analysis. The proposed system can be characterized as: • a bootstrap engine driven by the attributes of the images; • a solid framework supporting the process of hierarchical segmentation; • a universal platform for the development and integration of segmentation and analysis techniques; and • an extensible database in which knowledge about the image is accumulated. Central to this system are three major components: 1. a series of applications for attribute acquisition; 2. a standard format for attribute normalization; and 3. a database for attribute storage and data exchange between applications. The first step of the automatic process is to segment the mammogram hierarchically into several distinctive regions that represent the anatomy of the breast. The adequacy and quality of the mammogram are then assessed using the anatomical features obtained from segmentation. Further image analysis, such as breast density classification and lesion detection, may then be carried out inside the breast region. Several domain-specific algorithms have therefore been developed for the attribute acquisition component in the system. These include: 1. automatic pectoral muscle segmentation; 2. adequacy assessment of positioning and exposure; and 3. contrast enhancement of mass lesions. An adaptive algorithm is described for automatic segmentation of the pectoral muscle on mammograms of mediolateral oblique (MLO) views

Thesis (M.S.)--Florida State University, 2006. / Advisor: Piyush Kumar, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains viii, 45 pages. Includes bibliographical references.

Thesis (M.S.)--University of Tennessee, Knoxville, 2010. / Title from title page screen (viewed on July 20, 2010). Thesis advisor: Paul Ayers. Vita. Includes bibliographical references.

Ioversol and Iomeprol are radiological contrast media commonly used interchangeably in many South African imaging facilities for coronary angiography. Despite differences in chemical composition, they are presumed to have similar renal safety profiles. However, no studies directly compare the renal safety of these two contrast media for coronary angiography in a predominantly healthy population. A systematic review was performed to establish which contrast medium is safer. Articles were sourced from Medline, CINAHL, Scopus, Science Direct, and PubMed Clinical Queries databases. Eligible studies were peer-reviewed articles of coronary angiography examinations carried out on a healthy adult population, where Ioversol or Iomeprol or both were administered, with contrast-induced nephropathy as an end-point. Six articles with a total population of 2431 patients were selected. The Cochrane Risk of Bias Tool was used in evaluating included articles. Pooling studies using the random effects model did not show a statistically significant reduction in contrast-induced nephropathy when Iomeprol was administered (Risk ratio 1.14, 95% confidence interval 0.797-1.643, p = 0.466). Moderate heterogeneity (I2=54.21%) across the studies was observed. Study limitations included potential bias during data extraction because this was performed by a single reviewer, and language restrictions to include only English titles. Iomeprol may be better for use in the clinical setting because of more a predictable renal safety profile. / Health Studies / M. P. H. (Health Studies)