Browsing by Subject "Diagnostic imaging"
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Item Automatic segmentation of vertebrae from digitized x-ray images(Texas Tech University, 2002-12) Zamora-Camarena, GilbertoThe segmentation of vertebrae in x-ray images is of prime importance in the assessment of abnormalities of the spine. Manual segmentation is prone to errors due to inter- and intra-subject variabilities due to the subjective judgement that is employed. The use of computer vision methods is, therefore, an attractive alternative to providing an automatic means for segmenting vertebrae. However, general-purpose algorithms present a number of shortcomings that limit their ability to locate and delineate precise vertebral shapes. Therefore, there is a need for a different approach. This work presents the development of an automatic segmentation methodology that employs a hierarchical approach to segmentation. The unique combination of the Generalized Hough Transform, Active Shape Models, and Deformable Models provides three levels of segmentation firom coarse to fine, respectively. Each algorithm has been customized to address the shortcomings of the other two, thus providing a robust framework. Generalized Hough Transform is used to estimate the pose of the spine within a target image. Then, the technique of Active Shape Models is used to find the boundaries of the vertebrae and to give a global approximation to their shape. Finally, the technique of Deformable Models is used to refine the shape of the vertebrae at key points of interest, such as anterior comers. Experimental results with a data set of 100 lateral views of cervical vertebrae and 100 lateral views of lumbar vertebrae have shown a success rate of 75% in finding boundaries of cervical vertebrae and 50% in lumbar vertebrae. The algorithm developed in this work represents a viable alternative to the currently available segmentation methods in which a unique combination of customized algorithms implements a hierarchical firamework.Item Color and texture analysis of cervix lesions(Texas Tech University, 2004-12) Tulpule, Bhakti MThis work focuses on selection of appropriate geometrical and color features for classification and morphological texture analysis for characterization of diagnostically significant vascular patterns embedded in cervical lesions observed in Colposcopic and Cervicographic images of the ectocervix. Morphological texture analysis included a sequence of operations to yield skeletonized vascular structures uniquely representing cancerous and non-cancerous tissue stractures which are not easily observed in Colposcopic and Cervicographic images. This algorithmic ability to classify and characterize the embedded vascular patterns in cervical lesions may lead to automated and precise diagnostic differentiation of underlying vascular structure.Item Dispersion in biomedical optical imaging systems(2006) Oh, Sanghoon; Milner, Thomas E.Dispersion caused by the refractive index variation over a spectral range is an important characteristic to identify the structure and composition of materials. This research reports on work to obtain dispersion information using both time and spectral domain optical coherence tomography. To process time-frequency data, a non-uniform Fourier transformation is applied to remove the resolved non-uniform frequency sampling. Analysis of the spectral phase function in the optical frequency domain is applied to measure the dispersion. First, this research experimented with water (H2O) to measure dispersion. The measured dispersion of water is compared with known data to confirm the methodology. Second, the concentration of a glucose solution was estimated by analyzing the spectral phase function. The result showed that this method can provide an ability to measure glucose concentration with high sensitivity 0.54 mM. In conclusion, this method can be implemented to monitor sample constituents and to compensate for material dispersion.Item Integrated system for ultrasonic, elasticity and photoacoustic imaging(2008-08) Park, Suhyun, 1977-; Emelianov, Stanislav Y.By integrating three complementary imaging techniques - ultrasound, elasticity and photoacoustic imaging, a hybrid imaging system utilizing an array transducer is proposed for various biomedical imaging applications including cancer detection, diagnosis and therapy monitoring. Simultaneous imaging of the anatomy (ultrasound imaging), changes in biomechanical properties (elasticity imaging) and cancer-induced angiogenesis (photoacoustic imaging) of tissue is based on many synergistic features of these modalities and may result in a unique and important imaging tool. In this study, numerical analysis and experimental studies are presented to demonstrate the feasibility, to evaluate the performance, and also to improve the quality of the combined array-based ultrasound, elasticity and photoacoustic imaging system. To estimate spatial resolution, a point source was imaged using ultrasound and photoacoustic imaging modes. Then, several tissue mimicking phantoms were examined using ultrasound, photoacoustic and elasticity imaging. In elasticity imaging, ultrasound frames were acquired during deformation of the tissue. To reduce the data acquisition time of the system, high frame rate imaging was used. High frame rate imaging is possible by transmitting a broader and less focused ultrasound beam but the image quality is sacrificed. Thus, we compared the quality of the high frame rate and conventional ultrasound images. In photoacoustic imaging, acoustic transients are generated simultaneously in the entire volume of the laser irradiated tissue. Hence, image formation (beamforming) algorithms were developed based on the characteristics of the photoacoustic signals. Then, adaptive beamforming method is suggested to improve the image quality of the photoacoustic imaging. The results of the numerical analyses and experimental studies clearly indicate that ultrasound, elasticity and photoacoustic imaging techniques complement each other and together provide critical information needed for the reliable detection and diagnosis of diseases.Item Non-invasive optical diagnostics of cartilage(2002) Youn, Jong-in; Milner, Thomas E.With progressive use of lasers in medical applications, a recent focus of cartilage research has resulted in many reports on the investigation of the photobiological effects as well as development of non-invasive optical diagnostic techniques. Studies of the physical process underlying laser-induced stress relaxation have shown a number of mechanical, thermal and optical effects following laser reshaping of cartilage that need to be better understood to optimize the reshaping procedure for clinical applications. In the study of pathological degradation of cartilage such as osteoarthritis, understanding the kinetics of swelling and deformational behavior as well as morphological changes that occur in response to applied electric stimulation will be important to delineate the electro- mechanical mechanisms and rate- limiting processes that govern electromechanical behavior. Studies described in my dissertation are directed toward development of optical feedback control techniques for laser-assisted cartilage reshaping, and optical diagnosis for osteoarthritis. Although my work was directed toward these objectives, solution of many associated problems in the course of my work require scientific and engineering developments that may have benefits outside of those demonstrated here. In feedback control for laser assisted cartilage reshaping, preliminary photothermal effect assessment was performed using Fourier transform infrared spectroscopy. Results of this study may be useful for quantitative investigation of the relationship between the clinically important phenomenon of accelerated stress relaxation and kinetics of macromolecular denaturation in cartilage. For feedback control for laser assisted cartilage reshaping, the depth-resolved phase retardation measurements were performed using polarization sensitive optical coherence tomography (PS-OCT). The measurements of phase retardation changes in cartilage accompanying laser irradiation may be useful to better identify the biophysical transformation responsible for stress relaxation in cartilage and develop an optical feedback control procedure. In optical diagnosis for osteoarthritis, electrokinetic surface displacement and optical phase delays depending on applied excitation voltage and frequency were measured in cartilage using differential phase optical coherence tomography (DP-OCT). The electrokinetic measurements with application o f electric voltage to excite deformation show the measured interferometric surface displacement increased with increasing applied voltage and decreased with increasing excitation frequency. In the electrokinetic response of cartilage, measured optical phase delay between the surface displacement response and excitation waveform varies inversely to the excitation frequency. The investigation of electrokinetic behavior using DP-OCT may be used to develop a non-invasive optical technique for providing a sensitive indicator of cartilage viability on the molecular-level and possibly detecting early degradative changes in cartilage associated with osteoarthritis.Item Reduction of light scattering in biological tissue : implications for optical diagnostics and therapeutics(2001-08) Vargas, Gracie; Welch, Ashley J., 1933-Item Reflectance-based optical diagnosis of epithelial pre-cancer: modeling spectroscopic measurements, fiber-optic probe design considerations, and analysis of tissue micro-optical properties(2005) Arifler, Dizem; Richards-Kortum, Rebecca, 1964-Optical diagnostic techniques have the potential to improve early detection of pre-cancerous changes in tissues. These techniques can be implemented in real time without the need for biopsy removal, and are expected to have major impact in clinical practice. This dissertation describes a series of modeling studies aimed at establishing an improved understanding of reflectance properties of normal and pre-cancerous epithelial tissues, with the ultimate goal of revealing the potential of reflectance-based optical diagnosis of epithelial pre-cancer. The first part of the dissertation presents Monte Carlo modeling studies to provide a quantitative understanding of contrast observed in reflectance spectra of normal and pre-cancerous epithelial tissues. Simulation results provide important insights into the specific contributions of different epithelial and stromal optical parameters to the overall spectral response. Predictions from simulations agree well with in vivo measurements from cervical tissue, and can successfully describe differences in spatially resolved reflectance spectra of normal and precancerous tissue sites. Monte Carlo modeling is also used to evaluate different fiber-optic probe geometries with respect to sampling depth and to propose a probe design that can resolve spectral information from epithelium and stroma. The proposed design can reveal diagnostic features inherent in optical signatures unique to each of the two tissue layers. The research presented in the rest of the dissertation is targeted towards analyzing the micro-optical properties of epithelial tissues. The Finite-Difference Time-Domain (FDTD) method, a popular computational technique for solution of problems in electromagnetics, is used to model light scattering from epithelial cells and collagen fibers. FDTD simulation results indicate that morphological and structural changes associated with pre-cancer progression lead to significant alterations in light scattering properties of these microscopic tissue constituents. The modeling studies presented in this dissertation provide a framework to meaningfully interpret optical signals obtained from epithelial tissues and to optimize design of optical sensors for in vivo reflectance measurements. The results obtained throughout this research will aid in development and assessment of optical spectroscopic and imaging techniques for early, noninvasive diagnosis of epithelial pre-cancer.Item Synthesis of lanthanide chelates for biomedical imaging(Texas Tech University, 2003-12) Goebel, Timothy Stephen O'GaraLanthanide chelates are a somewhat unique class of molecules that have proven to be useful in the biomedical field as contrast agents for disease detection. This is due to many factors including their extremely large Stokes' shift, generally around 300 nm, and millisecond fluorescent lifetimes. The ability of these molecules to produce fluorescence in the low or zero-background regime as well as low cytotoxicity makes this class of molecules excellent candidates for use as contrast agents for a wide variety of applications in biological settings. Here we present the simple preparation and spectroscopic characterization of a new Europium chelate contrast agent, based on the 1, 4, 7, 10-tctraazacyclododecane macrocycle (cyclen). Eu-QF(CTME) produces a bright pinkish red luminescence when excited with low photon fluxes of UV light, indicating its potential for use in the field of biomedical imaging as a fluorescent probe. To determine the efficacy of this molecule as a fluorescent probe for disease detection, both animal testing as well as testing in a human tissue culture system was preformed. The well documented DMBA-treated Golden Hamster Cheek pouch epithelial cancer model was employed with Eu-QF(CTME) used as a topical agent for the detection of diseased tissue. In this preliminary study, the agent was observed to associate with malignant lesions, as well as dysplastic tissue. This suggests that Eu-QF(CTME) could be used as a contrast agent to aid in identifying oral precancer and cancer lesions. The results from the cell uptake experiments demonstrates the potential of this molecule as a stain for cancer cells.