Thesis (M.S.)--California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on Jan. 20, 2010. Major professor: Dr. Dennis Derickson. "Presented to the Electrical Engineering Department faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Electrical Engineering." "December, 2009." Includes bibliographical references (p. 111).

Optical Coherence Tomography (OCT) is an optical tomography technique which provides high resolution non-invasive three-dimensional (3D) structural images of the sample based on coherent properties of light. The dissertation focuses on the use of OCT systems for detecting glaucoma, which is the second leading cause of blindness worldwide. First, as a prerequisite of analyzing ophthalmologic OCT images, a retinal sublayer segmentation algorithm is presented and implemented with GPU assisted computation. Then, a polarization-sensitive optical coherence tomography (PS-OCT) system was constructed for the study of glaucoma. Three closely related clinical and animal studies on early-stage glaucoma detection using either OCT or PS-OCT were performed. Statistical analysis of the study results indicates that the scattering property of retinal nerve fiber layer (RNFL) is the earliest indicator for glaucoma. Finally, to investigate the scattering properties of RNFL, a pathlength-multiplexed scattering-angle-diverse optical coherence tomography (PM-SAD-OCT) system was designed and built. PM-SAD-OCT images were collected from human and rodent retina as well as earthworm nerve cord. PM-SAD-OCT system shows promising potentials to detect neurodegenerative diseases including glaucoma. / text

Thesis (M.S.)--California Polytechnic State University, 2008. / Mode of access: Internet. Title from PDF title page, viewed on March 26, 2009. Major professor: Dennis Derickson, Ph.D. "Presented to the Electrical Engineering Department Faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the Master of Science degree in Electrical Engineering." "December 2008." Includes bibliographical references (p. 93-94). Will also be available on microfiche.

Thesis supervisor: Mona K. Garvin. Includes bibliographic references (p. 55-57).

Indiana University-Purdue University Indianapolis (IUPUI) / Background: Erosive tooth wear (ETW) is the loss of tooth substance due to chemo-mechanical action unrelated to bacteria. ETW affects approximately 46 percent of children/adolescents and 80 percent of adults in the U.S. Visual examination indices are available for the clinical assessment of ETW. Although useful, they are subjective and heavily based on the clinical experience of the examiner. Some quantitative techniques have been proposed and used for clinically assessing erosive tooth wear, including quantitative light-induced fluorescence, ultrasonic measurement, and more recently, polarization-sensitive optical coherence tomography (PS-OCT). Objective: The objective of this study was to explore the ability of PS-OCT to objectively measure erosive tooth wear on occlusal surfaces. Method: This study was conducted in two phases. In the first phase, 10 sound extracted human lower first premolars were selected and then exposed to tooth wear simulation gradually. PS-OCT and micro computed tomography (μ-CT) were used to evaluate enamel thickness of those premolars at the buccal cusp tip during the simulation. In phase 2, 40 extracted human lower first premolars with different severity levels of ETW on occlusal surfaces were selected based on the Basic Erosive Wear Examination (BEWE) index. A total of 10 teeth (n =10) were selected for each BEWE score (0/1/2/3). PS-OCT and μ-CT were used to evaluate the enamel thickness at the highest point on the occlusal surface. Results: There was good agreement between PS-OCT and μ-CT in both phases (phase 1: 0.89 and phase 2: 0.97) with no significant difference between PS-OCT and μ-CT. Conclusion: This result shows the potential of PS-OCT as reliable method for measuring enamel thickness and monitoring tooth wear progression on the occlusal surface

In the medical field, the detection and diagnosis of diseases continue to improve. Developments in diagnostic techniques have helped to improve treatment in the early stages and avoid many risks to patients. One relatively new diagnostic technique is optical coherence tomography (OCT), which is used in many medical applications to perform internal microstructure imaging of the human body at high resolution (typically 10 micro metre), at high speed and in real time. OCT is non-invasive and can be used as a contact or non-contact technique to obtain an image. In medicine, there are many applications that involve OCT, such as in ophthalmology, gastroenterology, cardiology and oncology. This work demonstrates the design, development and implementation of a high resolution swept laser OCT system for the imaging and diagnosis of tissues in laboratory and clinical experiments. It reports an investigation to measure the thickness of the peritoneal membrane and the use of optical imaging contrast agents such as gold nanorods. There is also an account of the design of an endoscope-catheter fast scanning OCT system for biomedical studies of the gastrointestinal tract and gynaecological areas. These results were achieved by using a swept tuneable laser source with a very high tuning speed of 16 kHz over a wide range of wavelengths: 1260 nm to 1390 nm. The laser sweeps across 110 nm at a 16 kHz repetition rate. The real axial line speed is limited by the source that is used in the OCT system. The axial resolution of the system is 7 µm and its transverse resolution is 15 µm. The bandwidth of the source is up to DeltaGamma = 110 nm, centred at Gamma0 = 1325 nm, and the coherent length is 7 µm. On the sample arm of the interferometer, the swept laser OCT technique is combined with an optical probe and endoscope in order to develop a novel diagnostic imaging device to visualize tissue in vivo for animal and human experimental trials.

This thesis presents the development of new optical coherence tomography imaging systems and techniques to improve in vivo 3D microvascular imaging. Specifically these systems and techniques were proposed to address three main problems with 3D Doppler optical coherence tomography imaging: (a) Motion artefacts, (b) angle dependence of the signal, and (c) relatively high minimum detectable velocity of conventional color Doppler algorithms (~500 μm/s). In order to overcome these limitations a multi-pronged strategy was employed: (1) Construction of a retrospectively gated OCT system for the mitigation of periodic motion artefacts. Proof of principle in vivo B-mode imaging of Xenopus Laevis (embryo of African clawed frog) cardiovascular function up to 1000 frames per second (fps) from data acquired at 12 fps. Additionally, 4D imaging of the Xenopus Laevis heart at 45 volumes per second was demonstrated. (2) Construction of a Fourier domain mode locked laser for high speed swept source optical coherence tomography imaging. This laser was capable of reaching sweep rates of 67 kHz and was optimized to function in the SNR limited phase noise regimes upto approximately 55 dB structural SNR. (3) Development of a novel speckle variance image processing algorithm for velocity and angle independent 3D microvascular imaging. The velocity and angle independence of the technique was validated through phantom studies. iii In vivo demonstration of the speckle variance algorithm was performed by imaging the capillary network in the dorsal skin-fold window chamber model, with the results being validated using fluorescence confocal microscopy. In the final part of this thesis, these newly developed technologies were applied to the assessment of anti-vascular and anti-angiogenic therapies in preclinical models, specifically, photodynamic therapy and targeted degradation of HIF-α.

This thesis presents the development of new optical coherence tomography imaging systems and techniques to improve in vivo 3D microvascular imaging. Specifically these systems and techniques were proposed to address three main problems with 3D Doppler optical coherence tomography imaging: (a) Motion artefacts, (b) angle dependence of the signal, and (c) relatively high minimum detectable velocity of conventional color Doppler algorithms (~500 μm/s). In order to overcome these limitations a multi-pronged strategy was employed: (1) Construction of a retrospectively gated OCT system for the mitigation of periodic motion artefacts. Proof of principle in vivo B-mode imaging of Xenopus Laevis (embryo of African clawed frog) cardiovascular function up to 1000 frames per second (fps) from data acquired at 12 fps. Additionally, 4D imaging of the Xenopus Laevis heart at 45 volumes per second was demonstrated. (2) Construction of a Fourier domain mode locked laser for high speed swept source optical coherence tomography imaging. This laser was capable of reaching sweep rates of 67 kHz and was optimized to function in the SNR limited phase noise regimes upto approximately 55 dB structural SNR. (3) Development of a novel speckle variance image processing algorithm for velocity and angle independent 3D microvascular imaging. The velocity and angle independence of the technique was validated through phantom studies. iii In vivo demonstration of the speckle variance algorithm was performed by imaging the capillary network in the dorsal skin-fold window chamber model, with the results being validated using fluorescence confocal microscopy. In the final part of this thesis, these newly developed technologies were applied to the assessment of anti-vascular and anti-angiogenic therapies in preclinical models, specifically, photodynamic therapy and targeted degradation of HIF-α.

Optical coherence tomography (OCT) is an innovative modern biomedical imaging technology that allows in-vivo, non-invasive imaging of biological tissues. At present, some of the major challenges in OCT include the need for fast data acquisition system for probing fast developing biochemical processes in biological tissue, for image processing algorithms to reduce speckle noise and to remove motion artefacts, and for dispersion compensation to improve axial resolution and image contrast. To address the need for fast data acquisition, a novel, high speed (47,000 A-scans/s), ultrahigh axial resolution (3.3μm) Fourier Domain Optical Coherence Tomography (FD-OCT) system in the 1060nm wavelength region has been built at the University of Waterloo. The system provides 3.3μm image resolution in biological tissue and maximum sensitivity of 110 dB. Retinal tomograms acquired in-vivo from a human volunteer and a rat animal model show clear visualization of all intra-retinal layers and increased penetration into the choroid. OCT is based on low-coherence light interferometry. Thus, image quality is dependent on the spatial and temporal coherence properties of the optical waves back-scattered from the imaged object. Due to the coherent nature of light, OCT images are contaminated with speckle noise. Two novel speckle noise reduction algorithms based on interval type II fuzzy sets has been developed to improve the quality of the OCT images. One algorithm is a combination of anisotropic diffusion and interval type II fuzzy system while the other algorithm is based on soft thresholding wavelet coefficients using interval type II fuzzy system. Application of these novel algorithms to Cameraman test image corrupted with speckle noise (variance=0.1) resulted in a root mean square error (RMSE) of 0.07 for both fuzzy anisotropic diffusion and fuzzy wavelet algorithms. This value is less compared to the results obtained for Wiener (RMSE=0.09), adaptive Lee (RMSE=0.09), and median (RMSE=0.12) filters. Applying the algorithms to optical coherence tomograms acquired in-vivo from a human finger-tip show reduction in the speckle noise and image SNR improvement of ~13dB for fuzzy anisotropic diffusion and ~11db for fuzzy wavelet. Comparison with the Wiener (SNR improvement of ~3dB), adaptive Lee (SNR improvement of ~5dB) and median (SNR improvement of ~5dB) filters, applied to the same images, demonstrates the better performance of the fuzzy type II algorithms in terms of image metrics improvement. Micrometer scale OCT image resolution is obtained via use of broad bandwidth light sources. However, the large spectral bandwidth of the imaging beam results in broadening of the OCT interferogram because of the dispersive properties of the imaged objects. This broadening causes deterioration of the axial resolution and as well as loss of contrast in OCT images. A novel even-order dispersion cancellation interferometry via a linear, classical interferometer has been developed which can be further expanded to dispersion canceled OCT.

Optical coherence tomography (OCT) is an innovative modern biomedical imaging technology that allows in-vivo, non-invasive imaging of biological tissues. At present, some of the major challenges in OCT include the need for fast data acquisition system for probing fast developing biochemical processes in biological tissue, for image processing algorithms to reduce speckle noise and to remove motion artefacts, and for dispersion compensation to improve axial resolution and image contrast. To address the need for fast data acquisition, a novel, high speed (47,000 A-scans/s), ultrahigh axial resolution (3.3μm) Fourier Domain Optical Coherence Tomography (FD-OCT) system in the 1060nm wavelength region has been built at the University of Waterloo. The system provides 3.3μm image resolution in biological tissue and maximum sensitivity of 110 dB. Retinal tomograms acquired in-vivo from a human volunteer and a rat animal model show clear visualization of all intra-retinal layers and increased penetration into the choroid. OCT is based on low-coherence light interferometry. Thus, image quality is dependent on the spatial and temporal coherence properties of the optical waves back-scattered from the imaged object. Due to the coherent nature of light, OCT images are contaminated with speckle noise. Two novel speckle noise reduction algorithms based on interval type II fuzzy sets has been developed to improve the quality of the OCT images. One algorithm is a combination of anisotropic diffusion and interval type II fuzzy system while the other algorithm is based on soft thresholding wavelet coefficients using interval type II fuzzy system. Application of these novel algorithms to Cameraman test image corrupted with speckle noise (variance=0.1) resulted in a root mean square error (RMSE) of 0.07 for both fuzzy anisotropic diffusion and fuzzy wavelet algorithms. This value is less compared to the results obtained for Wiener (RMSE=0.09), adaptive Lee (RMSE=0.09), and median (RMSE=0.12) filters. Applying the algorithms to optical coherence tomograms acquired in-vivo from a human finger-tip show reduction in the speckle noise and image SNR improvement of ~13dB for fuzzy anisotropic diffusion and ~11db for fuzzy wavelet. Comparison with the Wiener (SNR improvement of ~3dB), adaptive Lee (SNR improvement of ~5dB) and median (SNR improvement of ~5dB) filters, applied to the same images, demonstrates the better performance of the fuzzy type II algorithms in terms of image metrics improvement. Micrometer scale OCT image resolution is obtained via use of broad bandwidth light sources. However, the large spectral bandwidth of the imaging beam results in broadening of the OCT interferogram because of the dispersive properties of the imaged objects. This broadening causes deterioration of the axial resolution and as well as loss of contrast in OCT images. A novel even-order dispersion cancellation interferometry via a linear, classical interferometer has been developed which can be further expanded to dispersion canceled OCT.