Browsing by Subject "Imaging systems in medicine"
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Item A personal computer based fundus image processing system(Texas Tech University, 1987-05) Whiteside, Steven LeroyNot availableItem 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 Multi-disciplinary study of lanthanide chelates as multi-modal molecular imaging agents(Texas Tech University, 2004-05) Manning, Henry CharlesMolecular imaging is a powerful tool that has the ability to elucidate biochemical mechanisms and signal the early onset of disease. Lanthanide chelates represent a unique class of molecular imaging agents that can yield multi-modal signatures including long-lived fluorescence and magnetic resonance. The primary aim of this dissertation is to demonstrate the utility of Lanthanide chelate molecular imaging agents for contrast enhanced disease demarcation. Traditionally, Lanthanide chelate imaging agents have been non-targeted perfusion agents that distribute in-vivo based on charge and lipophilicity. It is shown here that the structural features of the chelate can be modified to facilitate tunable spectroscopic and biodistribution properties in-vivo. While our perfusion-based agents have demonstrated considerable utility, their principal limitation is specificity. For increased specificity, we synthesized a trifunctional Lanthanide chelate that possessed an antenna for metal sensitization, phosphonate acid pendant arms for chelation, and a carboxylate arm for conjugation to targeting moieties such as antibodies, peptides, or small molecule ligands. Recently, peripheral benzodiazepine receptor (PBR) overexpression has been reported in many types of disease. Small molecule ligands of the PBR, such as PK11195, have been shown to bind with high affinity and thus could be used as contrast agent targeting moieties. Therefore, we synthesized a structural analogue of PK11195 that facilitates C-terminal conjugation. This form was then coupled to the trifunctional Lanthanide chelate and complexed with Europium and Gadolinium (Ln-PK11195). With the Ln-PK11195 agent in hand, it was demonstrated that PBR overexpressing C6 glioma cells would actively uptake the agent and that Ln-PK11195 seemed to be localizing on the PBR. Additionally, multi-modal imaging (fluorescence and MR) was shown possible on a single group of cells incubated with a Eu-PKl 1195 and Gd- PK11195 cocktail. Next, we demonstrated PBR profiling on surgically resected human tissue samples using Eu-PKl 1195, indicating a possible use as a histopathology stain. Both cancerous and non-cancerous PBR expressing disease was labeled with the agent. Finally, we fully characterized the primary spectroscopic signatures of Ln- PK11195 (time-resolved fluorescence and MR) for sensitivity to pH. It was shown that Ln-PK11195 demonstrates adequate pH sensitivity to measure localized, intracellular pH in tissues.Item Statistical model of beam distortion by tissue inhomogeneities in tissue harmonic imaging(2004) Yan, Xiang; Hamilton, Mark F.In tissue harmonic imaging (THI) the images are formed using the second harmonic component that is generated nonlinearly when ultrasound propagates inside the body. THI improves image resolution by reducing effects of phase distortion and reverberation in the body wall layer. A statistical investigation was performed to quantify improvement achieved with THI in the presence of tissue inhomogeneity. The investigation was both theoretical and experimental. In the theoretical model, a thin random phase screen located just in front of the source approximates the effect of inhomogeneity in the body wall layer. The phase variations across the screen are characterized statistically by zero mean, small variance, and Gaussian spatial correlation function. An analytical solution was derived for the expected value of the intensity of the second harmonic for a source that radiates a focused Gaussian beam. Contributions due to the coherent and scattered field components appear as separate terms in the solution. Validity of the statistical solution was established by comparison with ensemble averages of direct numerical simulations. Evolution of the beam profile and variation in energy content of the scattered second harmonic as a function of phase screen statistics are discussed. In comparison with the scattered field at the source frequency, the scattered field at the second-harmonic frequency is shown to be more localized about the beam axis. The results demonstrate clearly and quantitatively how distortions due to phase aberrations near the source are reduced by THI. Numerical simulations were also performed for beams radiated from a focused circular source with uniform amplitude. These results exhibit similar behavior. Dependence of results from the theoretical model on the distance between the source and phase screen was investigated. A transformation based on geometrical acoustics was obtained that approximates the mean scattered field due to a phase screen at a given distance away from the source using the solution obtained when the phase screen is in the source plane. Use of multiple phase screens to approximate thick inhomogeneous layers was also investigated. Experiments performed with a focused circular source and phase screens created with randomly indented plastic plates confirm the general theoretical approach.Item Ultrasound and photoacoustic imaging to guide and monitor photothermal therapy(2008-12) Shah, Jignesh Mukesh, 1979-; Emelianov, Stanislav Y.Photothermal cancer therapy is a potential alternative to surgery and involves selective tissue destruction using thermal energy. Targeted photoabsorbers, used in conjunction with matching a continuous wave laser, make photothermal therapy both noninvasive and tumor-specific. However, to become clinically relevant, there is a need to develop an imaging technique to identify tissue composition and to detect the presence of photoabsorbers in the tumor volume before therapy; to monitor the temperature rise during therapy; and to assess the tumor damage after therapy. In this study, a combined ultrasound and photoacoustic imaging system was designed to assist photothermal therapy. The imaging system was tested on tissue mimicking phantoms, ex-vivo porcine tissue samples, ex-vivo mice and in-vivo mice. First, ultrasound imaging was utilized to differentiate between water-based and lipidbearing tissue. A combined ultrasound and photoacoustic imaging system was then assembled to identify the presence and spatial location of gold nanoparticles. Multiwavelength photoacoustic imaging was used to further confirm the presence of nanoparticles. Temperature monitoring algorithms, using both temperature-dependent time shifts in ultrasound signals and amplitude changes in photoacoustic signals, were developed. Finally, photothermal therapy was carried out on tumor-bearing nude mice using in-vivo ultrasound and photoacoustic imaging to identify the tumor boundary, detect the nanoparticles and monitor the temperature elevation. The results of the studies show that ultrasound and photoacoustic imaging provide complementary and clinically relevant information. Overall, there is potential of using the ultrasound and photoacoustic imaging system to plan, guide and monitor photothermal therapy.