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Dissertations / Theses on the topic 'Directional optical coherence tomography'
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1
Lin, Roger Chin. "Optical Coherence Tomography for the Screening of Donor Corneas and Examination of the Retinal Nerve Fiber Directional Reflectance." online version, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1144703489.
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Ciamacca, Marisa Lynn. "Foveal Phase Retardation Correlation with Henle Fiber Layer Thickness." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492631647528424.
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Muscat, Sarah. "Optical coherence tomography." Thesis, Connect to e-thesis, 2003. http://theses.gla.ac.uk/630/.
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Thesis (Ph.D.) - University of Glasgow, 2003.Ph.D. thesis submitted to the Department of Cardiovascular and Medical Sciences, Faculty of Medicine, University of Glasgow, 2003. Includes bibliographical references. Print version also available.
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Huang, David. "Optical coherence tomography." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12675.
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Xu, Weiming. "Offset Optical Coherence Tomography." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626870603439104.
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Malmström, Mikael. "Multi-angle Oblique Optical Coherence Tomography." Thesis, KTH, Laserfysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-72978.
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Optical Coherence Tomography (OCT) is a non-invasive high-resolutionmethod for measuring the reectance of scattering media in 1/2/3D, e.g.skin. The method has been used in a number of dierent medical elds andfor measurement of tissue optical properties.The software developed in this thesis is able to display features hidden ina shadowed volume by adding multiple OCT measurements taken at obliqueangles, a technique here called Multiple-Angle Oblique Optical CoherenceTomography (MAO-OCT).Three dierent objects with were measured at 5 to 9 angles. The measurementswere automatically and manually aligned in the software. They werealso tested with 6 dierent high pass intensity lters (HPIF) and reduced insize using 4 dierent methods to speed up calculations.The software's automatic alignment was tested with one tilted computergenerated test at 9 angles and with 5 dierent shadow strengths.With MAO-OCT it is possible to remove some eects of shadows in OCT,though it comes with a cost of reduced sharpness. The errors depend muchon the dierences in index of refraction in the sample.The software managed to automatically align 90% of the articial measurements,and 60% of the OCT measurements. The shadow strength andthe resize method had no noticeable eect on the automatic alignment of themeasurements.
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Alex, Aneesh. "Multispectral three-dimensional optical coherence tomography." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54164/.
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A spectral-domain OCT system operating at 1300 nm wavelength region, capable of acquiring 47,000 A-lines/s, was designed and developed. Its axial and transverse resolutions were ∼ 6 µm and ∼15 µm respectively. OCT images of human skin were obtained in vivo using three OCT systems, in order to find the optimal wavelength region for dermal imaging. 800 nm OCT system provided better image contrast over other two wavelength regions. Meanwhile, 1300 nm wavelength region was needed to obtain information from deeper dermal layers. To determine the effect of melanin pigmentation on OCT, images were taken from subjects with different ethnic origins. Interestingly, melanin pigmentation was found to have little effect on penetration depth in OCT. In vitro tumour samples, comprising samples with different degrees of dysplasia, were imaged at 800 nm, 1060 nm and 1300 nm wavelength regions to find the capability of OCT to diagnose microstructural changes occurring during tumour progression. 800 nm OCT system was capable to detect the malignant changes with higher contrast than other wavelength regions. However, higher wavelength regions were required to penetrate deeper in densely scattering tumour samples at advanced stages. OCT system operating at 1060 nm was combined with a photoacoustic imaging (PAT) system to obtain complementary information from biological tissues. This multimodal OCT/PAT system demonstrated its potential to deliver microstructural information based on optical scattering and vascular information based on optical absorption in living mice and human skin. The results indicate OCT as a promising imaging modality that can have profound applications in several areas of clinical diagnostic imaging.
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Hee, Michael Richard. "Optical coherence tomography of the eye." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10263.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 221-230).
by Michael Richard Hee.
Ph.D.
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Wang, Zhao. "Intravascular Optical Coherence Tomography Image Analysis." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364673682.
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Valdez, Ashley. "Snapshot Spectral Domain Optical Coherence Tomography." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/613413.
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Optical coherence tomography systems are used to image the retina in 3D to allow ophthalmologists diagnose ocular disease. These systems yield large data sets that are often labor-intensive to analyze and require significant expertise in order to draw conclusions, especially when used over time to monitor disease progression. Spectral Domain Optical Coherence Tomography (SD-OCT) instantly acquires depth profiles at a single location with a broadband source. These systems require mechanical scanning to generate two- or three-dimensional images. Instead of mechanically scanning, a beamlet array was used to permit multiple depth measurements on the retina with a single snapshot using a 3x 3 beamlet array. This multi-channel system was designed, assembled, and tested using a 1 x 2 beamlet lens array instead of a 3 x 3 beamlet array as a proof of concept prototype. The source was a superluminescent diode centered at 840nm with a 45nm bandwidth. Theoretical axial resolution was 6.92um and depth of focus was 3.45mm. Glass samples of varying thickness ranging from 0.18mm to 1.14mm were measured with the system to validate that correct depth profiles can be acquired for each channel. The results demonstrated the prototype system performed as expected, and is ready to be modified for in vivo applicability.
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Beitel, David. "Development of optical sources for optical coherence tomography." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112557.
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The development of two different classes of optical sources for TD-OCT and FD-OCT are presented in this thesis. The design of several low-cost, high-performance BBSs, based on the ASE of two SOAs and EDF, are presented. Two different configuration types that were designed in this thesis are found to be effective BBSs. These sources are implemented in a TD-OCT system and therefore imaging performance is discussed as well. Secondly, two different WSSs based on mode-locked SFRLs with applications in SS-OCT are presented.From our experimental results with BBSs, we conclude that: (1) S/C-band output produced by the ASE emitted from two cascaded SOAs can be effectively extended with L-band output produced from the ASE of EDF; (2) An even broader output is achievable by: coupling the C-band and L-band outputs from a C-band SOA and EDF respectively and then amplifying the coupled output through an S-band SOA; (3) OCT imaging systems employing a light source with an S+C+L band output, with a center wavelength of approximately 1520 nm, can achieve high penetration depths in biological tissue.
From our experimental results with SFRLs, we conclude that: (1) Our two SFRL configurations generate picosecond pulses with reasonably narrow linewidths: 0.2--0.5 nm, and a sweeping range of about 50 nm; (2) These SFRLs can function as laser swept sources by setting the driving frequency of the RF generator to a periodic ramping function.
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Alarousu, E. (Erkki). "Low coherence interferometry and optical coherence tomography in paper measurements." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514282140.
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This thesis describes the application of Low Coherence Interferometry (LCI) and Optical Coherence Tomography (OCT) in paper measurements. The developed measurement system is a combination of a profilometer and a tomographic imaging device, which makes the construction versatile and applicable in several paper measurement applications. The developed system was first used to measure the surface structure of paper.
Different grades of paper were selected to provide maximum variation in surface structure. The results show that the developed system is capable of measuring grades of paper from rough base paper to highly coated photo printing paper.
To evaluate the developed system in surface characterization, the roughness parameters of five laboratory-made paper samples measured with the developed system and with a commercial optical profilometer were compared. A linear correlation was found with roughness parameters Ra and Rq.
Next, the surface quality of paper was evaluated using LCI, a Diffractive Optical Element Based Glossmeter (DOG), and a commercial glossmeter. The results show linear correlation between Ra and gloss measured with the commercial glossmeter. The roughness Ra and averaged gloss measured with the DOG didn't give such a correlation, but a combination of these techniques provided local properties of gloss and surface structure, which can be used to evaluate the local surface properties of paper.
In the next study, determination of the filler content of paper using OCT is discussed. The measurement results show clear correspondence of the slope of the averaged logarithmic fringe signal envelope and the filler content.
The last studies focus on 2D and 3D imaging of paper using OCT and begin with imaging of a self-made wood fiber network. The visibility of the fibers was clear. Next, several refractive index matcing agents are studied by means of light transmittance and OCT measurements to find the best possible agent for enhancing the imaging depth of OCT in paper. Benzyl alcohol was found to have the best possible combination of optical, evaporation, and sorption characteristics, and it is applied in 2D and 3D visualizations of copy paper.
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Trifanov, Irina. "Fibre optical sources and systems for optical coherence tomography." Thesis, University of Kent, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593914.
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Optical Coherence Tomography (OCT) is a powerful imaging technology in biomedical research and medicine. It enables in situ. 3D visualization of tissue structure and pathology, without the need. to excise the tissue and resolution approaching that of histology. OCT has had the most clinical impact in ophthalmology, where it provides structural and quantit ative informat ion that cannot be obtained by any other modality. The objective of the work presented in this thesis was the development of new imaging methods and optical devices to progress the OCT technology in t erms of its versatility, as well as to improve on parameters such as resolution, wavelength availability, integration effort and reliability. One of the most desired features in high resolution imaging is the display of simultaneously generated confocal images. The implementation of a confocal channel at the core of an OCT with quasi-simultaneous display of both images is demonstrated by synchronous optical switching of the power in the reference arm of the interferometer with the scanner determining the line in the final raster. The 1.0-1.1 11m region of the optical spectrum emerged as an attractive option compared to the standard 700-900 nm region, due to increased penetration beyond the retina, into the choroid, and reduced scat tering. Therefore, in this thesis, two novel optical sources based on fiber optic technology at 1 micrometer have been researched, assembled and tested: (a) a broadband ASE source based on combination of Yb-doped and Nd-doped silica fibers . The source emits at a cent ral wavelength of 1060 nm with a full-width-halfmaximum exceeding 70 nrn and 20 m\V output power; and (b) a swept fiber laser source emitting at 1065 nm central wavelength, with :::::l 50 nm tuning range and 40 m Woutput average power. A simple solution to linearize the sweeping in wavenumber (optical frequency), as required for image rendering, is demonstrated. The two prototype sources have been packaged and their performances validated in fully func tional OCT systems.
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Bachmann, Adrian H. "Phase-locked Fourier domain optical coherence tomography /." Lausanne : EPFL, 2007. http://library.epfl.ch/theses/?nr=3847.
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Thèse Ecole polytechnique fédérale de Lausanne EPFL, no 3847 (2007), Faculté des sciences et techniques de l'ingénieur STI, Programme doctoral Photonique, Institut d'imagerie et optique appliquée IOA (Laboratoire d'optique biomédicale LOB). Dir.: Theo Lasser, Rainer Leitgeb.
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Jiao, Shuliang. "Polarization-sensitive Mueller-matrix optical coherence tomography." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/398.
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Measuring the Mueller matrix with optical coherence tomography (OCT) makes it possible to acquire the complete polarization properties of scattering media with three-dimensional spatial resolution. We first proved that the measured degree-of-polarization (DOP) of the backscattered light by OCT remains unity-a conclusion that validated the use of Jones calculus in OCT. A multi-channel Mueller-matrix OCT system was then built to measure the Jones-matrix, which can be transformed into a Mueller matrix, images of scattering biological tissues accurately with single depth scan. We showed that when diattenuation is negligible, the round-trip Jones matrix represents a linear retarder, which is the foundation of conventional PS-OCT, and can be calculated with a single incident polarization state although the one-way Jones matrix generally represents an elliptical retarder; otherwise, two incident polarization states are needed. We discovered the transpose symmetry in the roundtrip Jones matrix, which is critical for eliminating the arbitrary phase difference between the two measured Jones vectors corresponding to the two incident polarization states to yield the correct Jones matrix. We investigated the various contrast mechanisms provided by Mueller-matrix OCT. Our OCT system for the first time offers simultaneously comprehensive polarization contrast mechanisms including the amplitude of birefringence, the orientation of birefringence, and the diattenuation in addition to the polarization-independent intensity contrast, all of which can be extracted from the measured Jones or the equivalent Mueller matrix. The experimental results obtained from rat skin samples, show that Mueller OCT provides complementary structural and functional information on biological samples and reveal that polarization contrast is more sensitive to thermal degeneration of biological tissues than amplitude-based contrast. Finally, an optical-fiber-based multi-channel Mueller-matrix OCT was built and a new rigorous algorithm was developed to retrieve the calibrated polarization properties of a sample. For the first time to our knowledge, fiber-based polarization-sensitive OCT was dynamically calibrated to eliminate the polarization distortion caused by the single-mode optical fiber in the sample arm, thereby overcoming a key technical impediment to the application of optical fibers in this technology.
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Meer, Freek Jeroen van der. "Vascular applications of quantitative optical coherence tomography." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/89109.
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Fergusson, James. "Full field swept source optical coherence tomography." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/49959/.
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Optical Coherence Tomography (OCT) is a non-invasive volumetric imaging technique that offers micron scale resolution over several millimetres of depth penetration in tissue. The aim of the project was to develop Full Field Swept Source OCT (FFSSOCT), charting the specifications of the system throughout and drawing comparisons with available Fourier domain OCT (FDOCT) systems. A super luminescent diode (SLD) light source was tuned to different optical frequencies using an acousto-optical tunable filter. The successive optical frequencies were distributed across the sample in parallel and the sequential interference spectra were recorded with a high speed digital camera. Using a 5mW optical source at 850nm, 70dB sensitivity was ultimately achieved in a single five second acquisition, improving the original performance by 5dB and increasing acquisition and processing time significantly. Ex vivo retinal images of rat and tree shrew were recorded with multiple layers visible. All software was custom written in Labview, improving the user interface and processing time over the existing Matlab code. To enhance the performance of the system, the camera was subsequently upgraded from 15 to 45% quantum efficiency and from 250k to 1.3M pixels. The light source was also upgraded to 20mW. The software was improved with spectral processing and dispersion compensation. 85dB sensitivity was ultimately achieved. Further ex vivo retinal images were taken, showing comparative image quality to those of the same retinal samples recorded with FDOCT. Further attempts to increase the system performance were limited by internal reflections and interfering surfaces within the FFSSOCT design leading to saturation of the digital camera. In vivo imaging was attempted using software based phase jitter compensation. Improvement could be seen with simple reflecting structures.
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Tung, Kai-Pin. "Coronary segmentation in intravascular optical coherence tomography." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24126.
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Cardiovascular disease (CVD) is a fatal disease of the heart or blood vessels. The greatest number of deaths from CVD is coronary heart disease (CHD). It is characterised by thickening of the arterial vessel wall due to atheromatous plaque which may result in narrowing or even occlusion of arterial lumen. Currently, intravascular optical coherence tomography (IVOCT) has been increasingly used in the clinic for the diagnosis of CHD because it permits high-resolution direct tomographic visualisation of cross-sectional images. With IVOCT techniques, stenosis and restenosis caused by plaques and neointima can be detected and analysed. The first main contribution of the thesis is a technique for the automatic segmentation of the lumen border when the guide-wire artifacts are noticeable. The proposed segmentation technique is capable of eliminating guide-wire artifacts and generating accurate lumen borders from IVOCT sequences. Compared to commercially available systems, the proposed method is robust and accurate. The second main contribution of this thesis is an approach for the stent strut detection that can detect stent struts when their intensity responses are weak. This technique is based on stent strut shadow detection. The innovative aspect of our technique is that, for every detected strut shadow, a-priori probability map is applied to estimate the stent strut position. With the detected stent struts, a stent area can be estimated to analyse the neointima hyperplasia (NIH) thickness in IVOCT sequences. The thesis also proposes an approach for the neointima segmentation without any information of the stent but instead with the lumen border. The approach is a combination of a multi-atlas based segmentation approach and a patch-based segmentation approach. With the approach, the neointima label can be obtained by fusing labels from atlases. Compared to other label fusion approaches, a significant increase in segmentation accuracy can be observed.
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Chang, Whan Wook. "Functional optical coherence tomography for clinical otolaryngology." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12730.
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Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Cross-sectional imaging of rapidly vibrating tissues or biomaterials under rapid periodic motion is useful for medical diagnosis and tissue engineering. Optical coheret:tce tomography (OCT) is a powerful technique, but its relatively low frame rates limited its use in such applications. Here, we present a novel method that enables capturing 4-dimensional (4D) images of samples in motion at oscillation frequencies of up to 10kHz and potentially far beyond. Employing continuous axial-line acquisition, motion-triggered beam scanning, and subsequent space-time registration, phase-aligned snapshots of tissue oscillation over the entire vibratory cycle can be obtained. This technique is applied to structural and functional imaging of major systems of speech and hearing: aerodynamically driven vibrations of the vocal fold in an ex vivo calf larynx and acoustically driven vibrations of the middle ear in an ex vivo chinchilla and human cadaveric temporal bones. Oscillations of the surface and interior structure of both organs can be viewed and analyzed with high three-dimensional resolution of 10-15 µm, and temporal resolution of 20 µs· For functional middle ear imaging, we employed phase sensitive OCT to achieve sub-nanometer scale vibration sensitivity to differentiate simulated pathologies. The results suggest that the dynamic 4D OCT technique has the potential to become a powerful tool in clinical and research applications for assessing health and mechanical properties of vocal folds and middle ear in the field of otolaryngology.
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Byers, Robert. "Clinical applications of angiographic optical coherence tomography." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/21904/.
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Angiographic optical coherence tomography (OCTA) has rapidly found utility within many facets of medical research. Here OCTA algorithms are enabled on a commercial OCT system and verified through correlation with intra-vital light microscopy (IVM). While the vast majority of vessels were accurately measured, smaller vessels (< 30μm) have a tendency to appear dilated in comparison to IVM. The technique was also expanded upon to facilitate the imaging of subcutaneous murine fibrosarcoma tumours, negating the requirement for an intra-vital window. It was found that vessel measurement sensitivity was sufficiently high such that the morphologies of vessels within tumours expressing unique vascular endothelial growth factor (VEGF) isoforms could be differentiated, potentially providing a new angle of approach in the study of anti-angiogenic treatments. OCTA was then applied to human studies of atopic dermatitis, where it was found that metrics corresponding to vessel depth and morphology could be correlated with the sub-clinical severity of the condition. Knowledge of this could be utilised to observe the therapeutic response to treatment, past the point of clinical remission. A range of image-processing techniques were also developed, including automatic segmentation of the epidermal layer within skin being utilised to quantify the degree of epidermal thinning in response to applied skin strain, calculation of the skin capillary loop density and the response of skin vessels to temperature and pressure.
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Arthur, Donna Louise. "Doppler optical coherence tomography for microcirculation studies." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/doppler-optical-coherence-tomography-for-microcirculation-studies(a18d59c3-6cfb-4266-98b1-188040bc120f).html.
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This thesis forms part of an ongoing long-term project to investigate the suitability of Doppler optical coherence tomography (OCT) as a measurement tool to investigate skin thickness and blood flow in patients with systemic sclerosis. There is a discussion of the characterisation of an electro-optic phase modulator for use in a Doppler OCT imaging system which is being built for the purpose of clinical studies. In addition to this the development of software for the same system is described. The work includes a comparison of two methods of obtaining Doppler information that were tested with the system; a phase resolved method and a correlation mapping method. Initial structural and Doppler images obtained using the system are presented. In addition to this the development of semi-automated software to measure skin thickness from both OCT and high frequency ultrasound images is discussed. The results of a study, for which this software was developed, into skin thickness measurements using both techniques in both patients with systemic sclerosis and healthy controls are presented. Both OCT and high frequency ultrasound were able to measure a statistically significant difference in epidermal thickness at multiple locations on the body. Finally, the modification of a freely available Monte Carlo simulation for light propagation in multi-layered tissue (MCML) to enable the simulation of structural and Doppler OCT images is covered. The simulation was able to extract the magnitude of the simulated flow accurately to within an order of magnitude, and after a simple filter was applied to eliminate fluctuations in the data the structure of the Doppler image closely matched what was modelled.
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Kirillin, M. (Mikhail). "Optical coherence tomography of strongly scattering media." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514287572.
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Abstract
Optical coherence tomography (OCT) is a modern rapidly developing technique for non-invasive imaging of the internal structure of optically non-uniform objects based on the principles of low-coherent interferometry. However, multiple scattering of light in the objects under study brings distortions to the images obtained by OCT. The analysis of formation of the OCT signals is required for understanding the role of multiple scattering in this formation and providing recommendations for optimal configuration of a measuring setup. In the present thesis formation of the OCT signals and images is analyzed implementing Monte Carlo simulations of light propagation in scattering media. Blood, intralipid solution, human skin and paper samples are chosen as the objects under study due to the interest in the diagnostics of these objects in biomedicine and paper industry.
Multilayer models of skin phantoms, skin and paper were developed in the frames of the present study for simulation of OCT signals and two-dimensional OCT images of these objects. The contribution of different scattering orders as well as different fractions of photons (least and multiply scattered, diffusive and non-diffusive) to these images was found allowing to evaluate the maximal depth of non-distorted imaging in each particular case.
The simulated OCT images were compared to the experimental ones demonstrating qualitative similarity. This fact allowed the author to analyze qualitatively the influence of parameters of the OCT setup on the images which have also been acquired in this work. The formation of the OCT images of paper samples with various refractive index matching liquids was also studied.
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Faber, Dirk Johannes. "Functional optical coherence tomography spatially resolved measurements of optical properties /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2005. http://dare.uva.nl/document/88794.
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Toadere, Florin. "Dispersion in optical configurations and sources for Optical Coherence Tomography." Thesis, University of Kent, 2017. https://kar.kent.ac.uk/64278/.
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Optical coherence tomography is a biomedical imaging technique employed to visualize tissue structure, ocular vasculature and blood flow. An OCT system is a non-invasive biomedical imaging system that provides bi-dimensional and three-dimensional images of biological tissue with micrometer scale resolution and millimeter scale depth range. In clinical application, OCT is employed in vivo imaging of the human eye. Swept source optical coherence tomography (SS-OCT) is the latest and fastest method of scanning. However, there are several disadvantages of the SS-OCT such as: the decrease of the roll-off sensitivity as the depth of scanning increases and the presence of mirror terms in the OCT images. The main objective of the work presented throughout this thesis was to evaluate the effects of dispersion on the performance of OCT. This study extends the research from the optical configurations at the core of OCT systems to the optical sources, where we show that dispersion can be usefully employed to obtain sweeping. We prove that an akinetic swept source (AKSS) can be devised for the important band of OCT, 800 nm, where there is still no MHz swept source available. In a Michelson interferometer a Fourier domain optical delay line was used for dispersion compensation that subsequently was employed to control the dispersion in an OCT system. A first goal of this thesis was to increase dispersion in order to evaluate the possibility of removing mirror terms from the OCT images. Therefore, three methods of dispersion measurement were evaluated. The first method measures the full width half maximum of the autocorrelation function. The second method uses a super continuous laser and an acoustic-optic tunable filter to measure the path dispersion in the position of the autocorrelation peak. A third method consists in a fitting method applied to channeled spectra collected from the interferometer when using a mirror. A second goal of this thesis was to prove the usefulness of employing dispersion in building a SS. In the process of akinetic swept source optimization, several types of dispersive fibres were tested and the most optimum conditions for driving a semiconductor optical amplifier were established. A dual mode locking scheme was used to tune the akinetic swept source at MHz rates. The axial range of the swept source was evaluated by scanning through the channeled spectrum of a Michelson interferometer.
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Siddiqui, Meena. "Optical domain subsampling for data-efficient optical coherence tomography (OCT)." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82390.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-100).
Recent advances in optical coherence tomography (OCT) have led to higher-speed sources that support imaging over longer depth ranges. Limitations in the bandwidth of state-of-the-art acquisition electronics, however, prevent adoption of these advances into clinical applications. This thesis introduces optical-domain subsampling as a method for increasing the imaging range while reducing the acquisition bandwidth. Optically subsampled lasers utilize a discrete set of wavelengths to alias fringe signals along an extended depth range into a bandwidth limited window. By detecting the complex fringe signals and under the assumption of a depth-constrained signal, optical domain subsampling enables recovery of the depth-resolved scattering signal without overlapping artifacts. Key principles behind subsampled imaging will be discussed, as well as the design criteria for an experimental subsampled laser. A description of the laser, interferometer, data acquisition system, and signal processing steps is given, and the results of point spread functions compressed into a baseband window are presented. Images that were taken with the subsampled OCT system and a wide-field microscope show that this imaging scheme is viable in vivo and can advantageously image samples that span a long depth range.
by Meena Siddiqui.
S.M.
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Tearney, Guillermo J. "Optical biopsy of in vivo tissue using optical coherence tomography." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10139.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 213-220).
by Guillermo James Tearney.
Ph.D.
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Silva, K. K. M. Buddhika Dilusha. "Optical coherence tomography : technology enhancements and novel applications." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0087.
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In the last fifteen years, a great deal of effort has been put forth, worldwide, for investigating and enhancing various aspects of optical coherence tomography (OCT). This thesis begins with a description of the technique of OCT, and an analysis of its underlying theory. The design and construction of an OCT system is described, with particular emphasis on a novel delay scanning method, and novel signal processing. Application of OCT to non-destructive characterisation of seeds, examination of skin lesions, measurement of fluid flow, and refractive index determination, are then demonstrated. Two technological enhancements to OCT are presented in this thesis. The first, an extended-range Fourier domain optical delay line (FDODL), extends the scan range of the traditional FDODL by a factor of almost 9, by scanning the galvanometer mirror around the region of zero tilt-angle. Polarisation optics are used to prevent light coupling back into the interferometer after only a single pass through the FDODL. A non-coplanar version of the FDODL is also presented, which overcomes the losses associated with the polarisation-based design, but trades off scan range to do so. Both versions of FDODL demonstrated excellent linearity and scan uniformity. The second technology presented here, bifocal optical coherence refractometry (BOCR), affords OCT the ability to measure refractive indices within turbid media. It achieves this by generating two confocal gates within the sample. From knowledge of the system parameters, and measurements of the confocal gate separation, the refractive index within the medium is evaluated to within ±0.01. Refractive index mapping is then demonstrated in a number of turbid samples. Three other applications of OCT are also demonstrated in this thesis. The first is the use of OCT to measure full thickness in lupin seeds. Although OCT could not penetrate the entire thickness of the hull, it is demonstrated that the variation in thickness of the two layers observed with OCT, explained 81% of the variation in thickness of the entire hull measured under a SEM. OCT was then applied, for what is believed to be the first time, in a large scale seed screening program. The second application is a preliminary investigation of the suitability of OCT to aid in the diagnosis of skin lesions. Although our system did not possess sufficient positioning accuracy to enable a direct one-to-one comparison between OCT and histology, a number of correspondences between OCT and histology images were demonstrated. The final application of OCT demonstrated here is a novel phase-locked-loop based demodulation scheme, to perform Doppler OCT. This demodulation scheme demonstrated a dynamic range of 98dB, a velocity range of ±20mm/s, and velocity resolution of 0.5mm/s. Using this system, laminar flow was demonstrated in milk flowing through a capillary tube.
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Zhang, Yaokun [Verfasser]. "Optical Coherence Tomography guided Laser-Cochleostomy / Yaokun Zhang." Karlsruhe : KIT Scientific Publishing, 2015. http://www.ksp.kit.edu.
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Akcay, Avni Ceyhun. "System design and optimization of optical coherence tomography." Doctoral diss., University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3586.
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Optical coherence imaging, including tomography (OCT) and microscopy (OCM), has been a growing research field in biomedical optical imaging in the last decade. In this imaging modality, a broadband light source, thus of short temporal coherence length, is used to perform imaging via interferometry. A challenge in optical coherence imaging, as in any imaging system towards biomedical diagnosis, is the quantification of image quality and optimization of the system components, both a primary focus of this research. We concentrated our efforts on the optimization of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps towards compact low-cost solutions. Up to recently, the criteria for the quality of a system was based on speed of imaging, sensitivity, and particularly axial resolution estimated solely from the full-width at half-maximum (FWHM) of the axial PSF with the common practice of assuming a Gaussian source power spectrum. As part of our work to quantify axial resolution we first brought forth two more metrics unlike FWHM, which accounted for side lobes in the axial PSF caused by irregularities in the shape of the source power spectrum, such as spectral dips. Subsequently, we presented a method where the axial PSF was significantly optimized by suppressing the side lobes occurring because of the irregular shape of the source power spectrum. The optimization was performed through optically shaping the source power spectrum via a programmable spectral shaper, which consequentially led to suppression of spurious structures in the images of a layered specimen. The superiority of the demonstrated approach was in performing reshaping before imaging, thus eliminating the need for post-data acquisition digital signal processing. Importantly, towards the optimization and objective image quality assessment in optical coherence imaging, the impact of source spectral shaping was further analyzed in a task-based assessment method based on statistical decision theory. Two classification tasks, a signal-detection task and a resolution task, were investigated. Results showed that reshaping the source power spectrum was a benefit essentially to the resolution task, as opposed to both the detection and resolution tasks, and the importance of the specimen local variations in index of refraction on the resolution task was demonstrated. Finally, towards the optimization of OCT and OCM for use in clinical settings, we analyzed the detection electronics stage, which is a crucial component of the system that is designed to capture extremely weak interferometric signals in biomedical and biological imaging applications. We designed and tested detection electronics to achieve a compact and low-cost solution for portable imaging units and demonstrated that the design provided an equivalent performance to the commercial lock-in amplifier considering the system sensitivity obtained with both detection schemes.Ph.D.
Optics and Photonics
Optics
30
Meemon, Panomsak. "Development of optical coherence tomography for tissue diagnostics." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4558.
Full textAbstract:
Endoscopic OCT utilizes a special miniature probe in the sample arm to access tubular organs inside the human body, such as the cardiovascular system, the lung, the gastrointestinal tract, the urinary tract, and the breast duct. We present an optical design of a dynamic focus endoscopic probe that is capable of about 4 to 6 micrometers] lateral resolution over a large working distance (i.e. up to 5 mm from the distal end of the probe). The dynamic focus capability allows integration of the endoscopic probe to GD-OCM imaging to achieve high resolution endoscopic tomograms. We envision the future of this developing technology as a solution to high resolution, minimally invasive, depth-resolved imaging of not only structure but also the microvasculature of in vivo biological tissues that will be useful for many clinical applications, such as dermatology, ophthalmology, endoscopy, and cardiology. The technology is also useful for animal study applications, such as the monitoring of an embryo's heart for the development of animal models and monitoring of changes in blood circulation in response to external stimulus in small animal brains.; However, the improvement in imaging speed of FD-OCT comes at the expense of a reduction in sensitivity to slow flow information and hence a reduction in detectable velocity range; 2) A structural ambiguity so-called 'mirror image' in FD-OCT prohibits the use of maximum sensitivity and imaging depth range; 3) The requirement of high lateral resolution to resolve capillary vessels requires the use of an imaging optics with high numerical aperture (NA) that leads to a reduction in depth of focus (DOF) and hence the imaging depth range (i.e. less than 100 microns) unless dynamic focusing is performed. Nevertheless, intrinsic to the mechanism of FD-OCT, dynamic focusing is not possible. In this dissertation, the implementation of PR-DOCT in a high speed swept-source based FD-OCT is investigated and optimized. An acquisition scheme as well as a processing algorithm that effectively extends the detectable velocity dynamic range of the PR-DOCT is presented. The proposed technique increased the overall detectable velocity dynamic range of PR-DOCT by about five times of that achieved by the conventional method. Furthermore, a novel technique of mirror image removal called 'Dual-Detection FD-OCT' (DD-FD-OCT) is presented. One of the advantages of DD-FD-OCT to Doppler imaging is that the full-range signal is achieved without manipulation of the phase relation between consecutive axial lines. Hence the full-range DD-FD-OCT is fully applicable to phase-resolved Doppler detection without a reduction in detectable velocity dynamic range as normally encountered in other full-range techniques. In addition, PR- DOCT can utilize the maximum SNR ratio provided by the full-range capability.; Microvasculature can be found in almost every part of the human body, including the internal organs. Importantly, abnormal changes in microvasculature are usually related to pathological development of the tissue cells. Monitoring of changes in blood flow properties in microvasculature, therefore, provides useful diagnostic information about pathological conditions in biological tissues as exemplified in glaucoma, diabetes, age related macular degeneration, port wine stains, burn-depth, and potentially skin cancer. However, the capillary network is typically only one cell in wall thickness with 5 to 10 microns in diameter and located in the dermis region of skin. Therefore, a non-invasive flow imaging technique that is capable of depth sectioning at high resolution and high speed is demanded. Optical coherence tomography (OCT), particularly after its advancement in frequency domain OCT (FD-OCT), is a promising tool for non-invasive high speed, high resolution, and high sensitivity depth-resolved imaging of biological tissues. Over the last ten years, numerous efforts have been paid to develop OCT-based flow imaging techniques. An important effort is the development of phase-resolved Doppler OCT (PR-DOCT). Phase-resolved Doppler imaging using FD-OCT is particularly of interest because of the direct access to the phase information of the depth profile signal. Furthermore, the high speed capability of FD-OCT is promising for real time flow monitoring as well as 3D flow segmentation applications. However, several challenges need to be addressed; 1) Flow in biological samples exhibits a wide dynamic range of flow velocity caused by, for example, the variation in the flow angles, flow diameters, and functionalities.; This capability is particularly useful for imaging of blood flow that locates deep below the sample surface, such as blood flow at deep posterior human eye and blood vessels network in the dermis region of human skin. Beside high speed and functional imaging capability, another key parameter that will open path for optical diagnostics using OCT technology is high resolution imaging (i.e. in a regime of a few microns or sub-micron). Even though the lateral resolution of OCT can be independently improved by opening the NA of the imaging optics, the high lateral resolution is maintained only over a short range as limited by the depth of focus that varies inversely and quadratically with NA. Recently developed by our group, 'Gabor-Domain Optical Coherence Microscopy' (GD-OCM) is a novel imaging technique capable for invariant resolution of about 2-3 micrometers] over a 2 mm cubic field-of-view. This dissertation details the imaging protocol as well as the automatic data fusion method of GD-OCM developed to render an in-focus high-resolution image throughout the imaging depth of the sample in real time. For the application of absolute flow measurement as an example, the precise information about flow angle is required. GD-OCM provides more precise interpretation of the tissue structures over a large field-of-view, which is necessary for accurate mapping of the flow structure and hence is promising for diagnostic applications particularly when combined with Doppler imaging. Potentially, the ability to perform high resolution OCT imaging inside the human body is useful for many diagnostic applications, such as providing an accurate map for biopsy, guiding surgical and other treatments, monitoring the functional state and/or the post-operative recovery process of internal organs, plaque detection in arteries, and early detection of cancers in the gastrointestinal tract.ID: 029050978; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 145-154).
Ph.D.
Doctorate
Optics and Photonics
31
Casaubieilh, P. "Fibre optic fizeau intererometer for optical coherence tomography." Thesis, Cranfield University, 2006. http://dspace.lib.cranfield.ac.uk/handle/1826/5664.
Full textAbstract:
The aim of the project was to develop the Fizeau interferometer configuration to
take advantage of the benefits derived from its “downlead insensitivity” to temperature
and polarisation fading. This sensing interferometer was investigated and implemented
in conjunction with various processing interferometers with the view to achieve
optimised performances for Optical Coherence Tomography (OCT) application.
A comprehensive theoretical analysis has been carried for Signal-to-Noise ratio of these
OCT systems.
Balanced detection indenting two detectors with anti-phase signals was also
investigated to improve further the SNR. The analysis showed that the SNR (67 dB) of
the balanced Fizeau interferometer improved by 30 dB from that of standard Fizeau
interferometer implementing a single detector. Experimentally, the best SNR for this
configuration was achieved by adding an electronic rectifier based demodulation system
for the signal after balanced detection.
The OCT systems investigated in this project were developed based on a
broadband source operating in the 1550 nm wavelength-band to facilitate improvement
in the depth of penetration of light directed into imaged samples. The coherence length
or axial resolution in air of the system was 21[micro milli]while the transverse resolution was 18
[micro milli] and focusing depth was 340 [micro milli].
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Ducros, Mathieu Gilles. "Polarization sensitive optical coherence tomography of the eye /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Song, Shaozhen. "Shear wave elastography based on optical coherence tomography." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/9cbb776c-35c1-4b5c-9fca-f00a8b603bd6.
Full textAbstract:
Mechanical properties of biological tissue are involved in a wide range of modern advances of medical science and technology. The mechanical property of biological tissue is directly related to the functionalities of tissue or organ, hence the in-depth knowledge of tissue mechanical property could lead to many benefits in medical research and health care. In clinical practice, accurate estimation of tissue mechanical property may facilitate to predict any possible pathological alterations, or to propose artificial intervention approaches. With the purpose of a quantitative, directly visualized estimation of biological tissue mechanical property, numerous research works in elastography have been conducted and had been successfully applied to countless clinical applications. Elastography techniques had been always rooted in medical imaging technique, classified into a range of scales, based on their imaging depth and resolution performance. In the scale of tissue micro structure, elastography is still a relatively new field, enabled by the recent advances in high-resolution medical imaging techniques e.g. high-frequency ultrasound imaging and Optical Coherence Tomography (OCT). The quantitative elastography technique based on OCT, known as quantitative optical coherence elastography (OCE) is a new research field, promising high-resolution quantitative elastography information with minimal contact that is not achievable by other imaging modalities. The aim of the thesis is to develop a multiple-functional OCT system to image the microstructure of biological tissue, meanwhile quantify localised mechanical property in the region of interest, and further apply it for pre-clinical research applications. Starting from the numerical model of mechanical waves, the behaviours of shear waves and surface waves in biological tissue is studied. Contact mechanical stimulations, as well as non-contact ultrasound and pulsed lasers are utilised to generate transient waves in biological samples. High speed shear wave imaging technique is developed and optimized based on a Phase-sensitive OCT (PhS-OCT) system to capture the transient wave propagation in samples, and the inversion algorithm for mapping localized shear modulus is proposed. The experimental results indicated that the Shear Wave Imaging OCT (SWI-OCT) technique is capable to provide abundant temporal and spatial resolution to capture the shear waves in tissuemimicking phantoms and in vivo biological samples. Quantitative elastography results were obtained from mouse skin and cornea samples, suggesting potential diagnostic and therapeutic clinical applications.
34
Chau, Alexandra H. (Alexandra Hung) 1980. "Elastography of coronary vessels using optical coherence tomography." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29943.
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Fujimoto, Masahiro. "Lacrimal Canaliculus Imaging Using Optical Coherence Tomography Dacryography." Kyoto University, 2019. http://hdl.handle.net/2433/242892.
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Jenkins, Michael W. "Imaging the Embryonic Heart with Optical Coherence Tomography." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1207340565.
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Fleming, Christine P. "Characterization of Cardiac Tissue Using Optical Coherence Tomography." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1270718628.
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Peric, Borislava. "Optical coherence tomography applied to investigations of optical properties of paintings." Thesis, Nottingham Trent University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.510265.
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Dubosson, Fabrice. "Optical coherence tomography : 3-D dental scanning imaging probe /." Sion, 2007. http://doc.rero.ch/search.py?recid=8351&ln=fr.
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Armstrong, Julian. "Anatomical optical coherence tomography in the human upper airway." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0022.
Full textAbstract:
[Truncated abstract] This thesis describes the development, clinical validation and initial application of a technique for taking measurements of the shape and dimensions of the human upper airway, called anatomical optical coherence tomography (aOCT). The technique uses a transparent catheter containing a rotating optical probe which is introduced transnasally and positioned in the airway and oesophagus. Optical coherence tomography is used to take calibrated cross-sectional images of the airway lumen as the probe rotates. The probe can also be advanced or withdrawn within the catheter during scanning to build up three-dimensional information. The catheter remains stationary so that the subject is not aware of the probe motion. The initial application of the system is research into obstructive sleep apnoea (OSA), a serious condition characterized by repetitive collapse of the upper airway during sleep and an independent risk factor for deaths by heart disease, strokes or car accidents. Measurement of upper airway size and shape is important for the investigation of the pathophysiology of OSA, and for the development and assesment of new treatments. . . We have used aOCT to capture three-dimensional data sets of the airway shape from upper oesophagus to the nasal cavity, undertaken measurements of compliance and other airway characteristics, and recorded dynamic airway shape during confirmed sleep apnoea events in a hospital sleep laboratory. We have shown that aOCT generates quantitative, real-time measurements of upper airway size and shape, allowing study over lengthy periods during both sleep and wakefulness. These features should make it useful for study of upper airway behavior to investigate OSA pathophysiology, and aid clinical management and treatment development.
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Woods, Daniel. "Selection in depth in Fourier domain optical coherence tomography." Thesis, University of Kent, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498894.
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Greenwood, Purnima. "Advanced quatum dot superluminescent diodes for optical coherence tomography." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548378.
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Wang, Jingyu. "Optical coherence tomography methods using 2-D detector arrays." Thesis, University of Kent, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.650808.
Full textAbstract:
Optical coherence tomography (OCT) is a non-invasive, non-contact optical technique that allows cross-section imaging of biological tissues with high spatial resolution, high sensitivity and high dynamic range. Standard OCT uses a focused beam to illuminate a point on the target and detects the signal using a single photodetector. To acquire transverse information, transversal scanning of the illumination point is required. Alternatively, multiple OCT channels can be operated in parallel simultaneously; parallel OCT signals are recorded by a two-dimensional (2D) detector array. This approach is known as Parallel-detection OCT. In this thesis, methods, experiments and results using three parallel OCT techniques, including full -field (time-domain) OCT (FF-OCT), full-field swept-source OCT (FF-SS-OCT) and line-field Fourier-domain OCT (LF-FD-OCT), are presented. Several 2D digital cameras of different formats have been used and evaluated in the experiments of different methods. With the LF-FD-OCT method, photography equipment, such as flashtubes and commercial DSLR cameras have been equipped and tested for OCT imaging. The techniques used in FF-OCT and FF-SS-OCT are employed in a novel wavefront sensing technique, which combines OCT methods with a Shack-Hartmann wavefront sensor (SH-WFS). This combination technique is demonstrated capable of measuring depth-resolved wavefront aberrations, which has the potential to extend the applications of SH-WFS in wavefront-guided biomedical imaging techniques.
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Xu, Jianbing, and 徐鉴冰. "Optical coherence tomography : from system design to spectroscopic applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206473.
Full textAbstract:
Optical coherence tomography (OCT), as a newly developed imaging modality, has attracted significant attention due to its capability to obtain the cross-sectional information of biological tissues in a non-invasive way, with resolution in the range of several micrometers. The third-generation swept source OCT (SS-OCT), is superior in the speed, imaging range and signal-to-noise ratio (SNR) compared with the previous time-domain OCT (TD-OCT) and spectral domain OCT (SD-OCT), and therefore forms our research focus.
In this thesis, for the first time, I investigate the deployment of Fourier domain mode-locked (FDML) swept laser by utilizing the bismuth-based erbium doper fiber (Bi-EDF) with a sweeping bandwidth of ~ 81nm achieved. Following, fiber Raman amplifier (FRA) is also investigated by employing multiple Raman pumps. The tuning range is ~111.8nm, which is much larger than the previous reported Raman pumped FDML in the 1550nm region. Imaging was performed to validate the feasibility of the proposed schemes for the SS-OCT applications, respectively.
In addition to the FDML swept laser cavity design, speckle noise reduction is also of great importance in OCT, which can significantly improve the visibility of the obtained OCT images. I demonstrate two different speckle reduction methods for OCT applications, which are superior in suppressing speckle noise and reserving the one-dimensional (1D) and two-dimensional (2D) signal information, respectively. Applying the proposed wavelet domain compounding (WDC) and contourlet shrinkage method to despeckle the OCT images, the visibility of the OCT images was significantly improved, with negligible edge preservation compromise.
Spectroscopic information is also of interest to many researchers as it provides additional spectroscopic contrast, which on one hand, will improve the visualization of the images, and on the other hand, will enable the classification of different tissue types and help the process of discrimination between invasive and noninvasive tumors. Compared with our previous reported work about dual-band spectroscopic OCT based on optical parametric amplifier (OPA) to generate another idler band, which will be used as the second band for dual-band spectroscopic analysis, I further extend the dual-band spectroscopic OCT to the endoscopic applications, and investigate the dual-band FDML swept laser configuration based on a custom-designed dual-channel driver to synchronize the two different wavelength bands, centered at 1310 and 1550 nm, respectively. OCT Images for different bands are captured and post-processed by coding the spectral difference in different colors.
In short, in this thesis, the investigations of OCT range from system design, speckle reduction to the spectroscopic applications. All these research efforts will extend the current FDML techniques for a wide range of SS-OCT applications. These schemes may be useful in OCT swept laser source build up, speckle noise reduction, and the extension of spectroscopic analysis.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
45
Chan, Chun-wang Aaron, and 陳俊弘. "Statistical estimation of haemodynamic parameters in optical coherence tomography." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206460.
Full textAbstract:
Optical coherence tomography (OCT) is an imaging modality analogous to ultrasound. By using the interference properties of light, one may image to micrometer resolutions using interferometric methods. Most modern systems can acquire A-scans at kHz to MHz speeds, and are capable of real-time 3D imaging. OCT has been used extensively in ophthalmology and has been used in angiography to quantify blood flow. The aim of this research has been to develop statistically optimal estimators for blood flow estimation to take advantage of these hardware advances. This is achieved through a deeper understanding of the noise characteristics of OCT. Through mathematical derivations and simulations, the noise characteristics of OCT Doppler and flow imaging were accurately modelled as additive white noise and multiplicative decorrelation noise. Decorrelation arises due to relative motion of tissue relative to the OCT region of interest and adversely affects Doppler estimation. From these models maximum likelihood estimators (MLEs) that statistically outperform the commonly used Kasai autocorrelation estimator were derived. The Cramer-Rao lower bound (CRLB), which gives the theoretical lowest estimator variance for an unbiased estimator was derived for different noise regimes. It is shown that the AWGN MLE achieves the CRLB for additive white noise dominant conditions, and the decorrelation noise MLE achieves the CRLB under more general noise conditions. The use of computational algorithms that enhance the capabilities of OCT are demonstrated. This shows that this approach for determining parametric estimators may be used in a more general medical imaging context. In addition, the use of decorrelation as a measure of speed is explored, as it is itself proportional to flow speed.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
46
Lee, Kye-Sung. "EXTENDED FOCUS RANGE HIGH RESOLUTION ENDOSCOPIC OPTICAL COHERENCE TOMOGRAPHY." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3085.
Full textAbstract:
Today, medical imaging is playing an important role in medicine as it provides the techniques and processes used to create images of the human body or parts thereof for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). Modalities are developing over time to achieve the highest possible resolution, speed of image acquisition, sensitivity, and specificity. In the past decade, advances in optics, fiber, as well as laser technology have enabled the development of noninvasive optical biomedical imaging technology that can also be applied to endoscopy to reach deeper locations in the human body. The purpose of this dissertation is to investigate a full system design and optimization of an optical coherence tomography (OCT) system to achieve high axial and lateral resolution together with an extended depth of focus for endoscopic in vivo imaging. In this research aimed at advancing endoscopic OCT imaging, two high axial resolution optical coherence tomography systems were developed: (1) a spectrometer-based frequency-domain (FD) OCT achieving an axial resolution of ~2.5 µm using a Ti:Sa femtosecond laser with a 120nm bandwidth centered at 800nm and (2) a swept-source based FD OCT employing a high speed Fourier domain mode locked (FDML) laser that achieves real time in vivo imaging with ~8 µm axial resolution at an acquisition speed of 90,000 A-scans/sec. A critical prior limitation of FD OCT systems is the presence of mirror images in the image reconstruction algorithm that could only be eliminated at the expense of depth and speed of imaging. A key contribution of this research is the development of a novel FD OCT imager that enables full range depth imaging without a loss in acquisition speed. Furthermore, towards the need for better axial resolution, we developed a mathematical model of the OCT signal that includes the effect on phase modulation of phase delay, group delay, and dispersion. From the mathematical model we saw that a Fourier domain optical delay line (FD ODL) incorporated into the reference arm of the OCT system represented a path to higher performance. Here we then present a method to compensate for overall system dispersion with a FDODL that maintains the axial resolution at the limit determined solely by the coherence length of a broadband source. In the development of OCT for endoscopic applications, the need for long depth of focus imaging is critical to accommodate the placement of the catheter anywhere within a vessel. A potential solution to this challenge is Bessel-beam imaging. In a first step, a Bessel-beam based confocal scanning optical microscopy (BCSOM) using an axicon and single mode fiber was investigated with a mathematical model and simulation. The BCSOM approach was then implemented in a FD OCT system that delivered high lateral resolution over a long depth of focus. We reported on the imaging in biological samples for the first time with a double-pass microoptics axicon that demonstrated clearly invariant SNR and 8 um lateral resolution images across a 4 mm depth of focus. Finally, we describe the design and fabrication of a catheter incorporated in the FD OCT. The design, conceived for a 5 mm outer diameter catheter, allows 360 degree scanning with a lateral resolution of about 5 um across a depth of focus of about 1.6 mm. The dissertation concludes with comments for related future work.Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
47
Charalambous, Ismini. "Distortion, randomness and quantitative measurements using optical coherence tomography." Thesis, University of Kent, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443780.
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Moger, Julian. "Investigating blood flow dynamics using Doppler optical coherence tomography." Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288701.
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Zuluaga, Andrés Felipe. "Contrast agents for tumor detection with optical coherence tomography /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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50
Armstrong, Julian. "Anatomical optical coherence tomography in the human upper airway /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0022.
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