Download or read book A Real time Optical Coherence Tomography System Utilizing an Acquisition and Signal Processing Architecture Implemented on a Field Programmable Gate Array written by Tyler Stephen Ralston and published by . This book was released on 2004 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Accelerating Fourier Domain Optical Coherence Tomography Using General Purpose Graphics Processing Units and Field Programmable Gate Arrays written by Jian Li and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fourier Domain Optical Coherence Tomography is an emerging biomedical imaging technology that provides ultra high resolution and a fast imaging speed. The complexity of the FD-OCT algorithm demands high processing power from the underlying platform. However, the scaling of faster data acquisition rates and 3D imaging on real time FD-OCT systems is quickly outpacing the performance growth of General Purpose Processors. Our research investigates the scalability of two potential platforms for accelerating FD-OCT -- GPGPUs and FPGAs. We implemented a FD-OCT system using a GPGPU as co-processor with 6.9x speed up. We also created a hardware processing engine using FPGAs, delivering over 2x the throughput rate over GPGPU with 1024- point FFT. Our analysis on the performance and scalability for both platforms shows that, while GPGPUs offer an easy and low cost solution for accelerating FD-OCT, FPGAs are more likely to match the long term demands for real-time, 3D FD-OCT.
Download or read book 3D Image Processing and FPGA Implementation for Optical Coherence Tomography written by Sylvia D. Carroll and published by . This book was released on 2013 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis discusses certain aspects of the noninvasive imaging technique known as optical coherence tomography (OCT). Topics include three-dimensional image rendering as well as application of the Fast Fourier Transform to reconstruct the axial scan as a function of depth. Implementations use LabVIEW system design software and a Xilinx Spartan-6 field-programmable gate array (FPGA). The inherent parallel-processing capability of an FPGA opens the possibility of designing a "super-sensor" which entails simultaneous capturing of image and sensor data, giving medical practitioners more data for potentially improved diagnosis. FPGA-based processing would benefit many methods of characterizing biological samples; OCT and photonic crystal microarray biosensors are discussed.
Download or read book Real time Photon noise Limited Optical Coherence Tomography Based on Pixel level Analog Signal Processing written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the development of a CMOS smart imager for real-time optical coherency tomography (OCT). OCT, a measuring technique based on low-coherence interferometry, allows the acquisition of three-dimensional pictures of discontinuities in the refractive index of the sample. Due to the achieved depth resolution in the micrometer range, it has gained a lot of impact not only for many biomedical but also for industrial applications over the last few years. OCT allows the determination of surfaces as well as the acquisition of tomographic images of transparent and turbid objects with an outstanding depth resolution in the sub-micrometer scale over a depth range of up to several millimeters. The goal of this thesis was the realization of a very fast, robust 3D OCT system performing at close to the physical limit. A multi-channel approach has been chosen and a CMOS smart imager has been developed as they key component of the total system that includes an appropriate electrical, optical, and mechanical system. This system proves that by the use of parallel optical coherence tomography (pOCT) in combination with custom designed CMOS image sensors, real-time imaging with compact devices is realizable. For time domain (TD- ) OCT, the reference path length of the interferometer is varied and a simultaneous amplitude demodulation of the optical signal generates the depth image. The cross-sectional or volumetric image of a conventional TD-OCT system is generated by combining many laterally shifted one-dimensional depth scans throughout the object. Therefore, very fast reference path scanners and one or two translation stages are required. This results in a non-negligible mechanical system complexity. In pOCT, the translation scanners are replaced by image-forming optics and a two-dimensional image sensor. This step reduces the depth scan speed greatly and renders 3D image acquisition in some tens of milliseconds possible. On the other hand, the image sensor requiremen.
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Real time Digital Signal Processing based Optical Coherence Tomography and Optical Doppler Tomography written by Alexander Werner Schaefer and published by . This book was released on 2001 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Extended Focus Range High Resolution Endoscopic Optical Coherence Tomography written by Kye-Sung Lee and published by . This book was released on 2008 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 [micrometers] 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 [micrometers] 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 [micrometers] 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 [micrometers] across a depth of focus of about 1.6 mm. The dissertation concludes with comments for related future work.
Download or read book Optical Coherence Tomography written by Mark E. Brezinski and published by Elsevier. This book was released on 2006-08-25 with total page 645 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical Coherence Tomography gives a broad treatment of the subject which will include 1)the optics, science, and physics needed to understand the technology 2) a description of applications with a critical look at how the technology will successfully address actual clinical need, and 3) a discussion of delivery of OCT to the patient, FDA approval and comparisons with available competing technologies. The required mathematical rigor will be present where needed but be presented in such a way that it will not prevent non-scientists and non-engineers from gaining a basic understanding of OCT and the applications as well as the issues of bringing the technology to the market. - Optical Coherence Tomography is a new medical high-resolution imaging technology which offers distinct advantages over current medical imaging technologies and is attracting a large number of researchers. - Provides non-scientists and non-engineers basic understanding of Optical Coherence Tomography applications and issues.
Download or read book Enabling Freehand Scanning of Optical Coherence Tomography Needle Probes Using a Magnetic Tracking System written by Boon Yew Yeo and published by . This book was released on 2012 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical coherence tomography (OCT) is an optical imaging modality that can perform real-time and in vivo imaging of biological tissue at micrometre-scale resolutions. Due to its limited imaging depth (1-2 mm) in turbid biological tissue, various forms of imaging probes have been designed to accommodate the need to image deeper into the human body, including intravascular probes for blood vessel imaging, endoscopic probes for hollow organ imaging, and needle probes, the focus of this study, for interstitial imaging of solid tissues and organs. OCT images are generated via a lateral beam scanning mechanism. Until recently, most OCT needle probes have been scanned using a motorised setup. Whilst highly accurate, the complexity of a motorized setup often makes the probe unwieldy and difficult to guide during probe deployment in a clinical environment. A more convenient approach would be to manoeuvre the needle probe by hand and perform freehand lateral scanning. The elimination of bulky scanning motors and associated electronics facilitates the development of a miniaturized handheld probe, and the high degree of freedom provided by a freehand scanning method aids in smooth control and guidance of the needle probe. However, hand motion inevitably contains variations in speed and orientation, which can result in geometric distortion in the reconstructed image if unaccounted for. Although motion tracking methods could be used to improve these artefacts, the requirement to track at the micrometre scale is not readily met by many established methods. This thesis presents the use of a magnetic tracking system with an OCT needle probe to correct for the geometrical distortions introduced by freehand scanning. Due to the insufficient resolution of currently available magnetic trackers, two signal processing techniques were implemented to improve the resolution and accuracy of the magnetic tracking method. A proof-of-principle system was developed, and successful image reconstruction was demonstrated on the freehand scanning of tissue-mimicking phantoms and biological tissue, maintaining the micrometre-scale resolutions of OCT. The accuracy of the method was measured to be 18 U+006fm RMS, and the method was shown to be able to account for changes in both the scanning speed and the orientation of the probe. This freehand scanning method could contribute toward clinical implementation of OCT needle imaging.
Download or read book Progress Towards Detecting Neural Activity in Optical Coherence Tomography Using Phase written by Jasmine Kavan Shah and published by . This book was released on 2017 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical Coherence Tomography (OCT) is non-invasive, real time optical imaging method based on low coherence interferometry with high resolution. It is capable of imaging microstructure by measuring the light backscattered from the sample. Under the AGI grant, I have built a Swept Source OCT (SS-OCT) / phase resolved OCT to detect the nanometer(nm) scale changes in the cell membrane that occur during membrane depolarization and Ion influx. This type of small changes can be seen using phase. Intensity is robust but is less sensitive to the small-scale changes whereas phase is highly sensitive. The noise level for phase difference quantification depends on the lateral motion, triggering of the wavelength mismatch and signal to noise ratio (SNR). To detect the nm scale changes phase noise should be minimum. The phase noise is inversely proportional to SNR. The SNR of the system should be maximum. The SS-OCT has swept source with sweep rate 100 kHz and it is not phase stable. It needs post processing algorithm to match the triggering wavelength to stabilize the phase. I wrote the code in GPU to reduce the computation time for post processing algorithm. Due to a few setbacks related to moving the system to a collaborating lab, the biological portion of my thesis work, trying to find the neural activity in the walking leg nerve of the Lobster using phase, was done with a spectral domain OCT (SD-OCT). To see any action potential change in the nerve I realigned the SD-OCT system with center wavelength to increase the SNR of the system and the sample arm with the nerve chamber (3D printed) to stimulate the nerve at one end and take the OCT image at the other end to see the action potential.
Download or read book Evaluation of State of the Art Hardware Architectures for Fast Cone Beam CT Reconstruction written by Holger Scherl and published by Springer Science & Business Media. This book was released on 2011-07-29 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Holger Scherl introduces the reader to the reconstruction problem in computed tomography and its major scientific challenges that range from computational efficiency to the fulfillment of Tuy's sufficiency condition. The assessed hardware architectures include multi- and many-core systems, cell broadband engine architecture, graphics processing units, and field programmable gate arrays.
Download or read book Image Processing in Optical Coherence Tomography Using Matlab written by Robert Koprowski and published by Robert Koprowski. This book was released on 2011 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the results of the creation of methods for ophthalmologists support in OCT images automated analysis. These methods, like the application developed on their basis, are used during routine examinations carried out in hospital. The monograph comprises proposals of new and also of known algorithms, modified by authors, for image analysis and processing, presented on the basis of example of Matlab environment with Image Processing tools. The results are not only obtained fully automatically, but also repeatable, providing doctors with quantitative information on the degree of pathology occurring in the patient. In this case the anterior and posterior eye segment is analysed, e.g. the measurement of the filtration angle or individual layers thickness. To introduce the Readers to subtleties related to the implementation of selected fragments of algorithms, the notation of some of them in the Matlab environment has been given. The presented source code is shown only in the form of example of implementable selected algorithm. In no way we impose here the method of resolution on the Reader and we only provide the confirmation of a possibility of its practical implementation.
Download or read book Real time Photon noise Limited Optical Coherence Tomography Based on Pixel level Analog Signal Processing written by Stephan Beer and published by . This book was released on 2006 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of Optical Coherence Tomography for Tissue Diagnostics written by Panomsak Meemon and published by . This book was released on 2010 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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. 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. 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. 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.
Download or read book Optical Coherence Tomography written by Jianbing Xu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Optical Coherence Tomography: From System Design to Spectroscopic Applications" by Jianbing, Xu, 徐鉴冰, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: 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. DOI: 10.5353/th_b5317037 Subjects: Optical coherence tomography
Download or read book Optical Coherence Tomography written by Wolfgang Drexler and published by Springer. This book was released on 2010-11-16 with total page 1346 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical coherence tomography (OCT) is the optical analog of ultrasound imaging and is emerging as a powerful imaging technique that enables non-invasive, in vivo, high resolution, cross-sectional imaging in biological tissue. This book introduces OCT technology and applications not only from an optical and technological viewpoint, but also from biomedical and clinical perspectives. The chapters are written by leading research groups, in a style comprehensible to a broad audience.
Download or read book Application of FPGA to Real Time Machine Learning written by Piotr Antonik and published by Springer. This book was released on 2018-05-18 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book lies at the interface of machine learning – a subfield of computer science that develops algorithms for challenging tasks such as shape or image recognition, where traditional algorithms fail – and photonics – the physical science of light, which underlies many of the optical communications technologies used in our information society. It provides a thorough introduction to reservoir computing and field-programmable gate arrays (FPGAs). Recently, photonic implementations of reservoir computing (a machine learning algorithm based on artificial neural networks) have made a breakthrough in optical computing possible. In this book, the author pushes the performance of these systems significantly beyond what was achieved before. By interfacing a photonic reservoir computer with a high-speed electronic device (an FPGA), the author successfully interacts with the reservoir computer in real time, allowing him to considerably expand its capabilities and range of possible applications. Furthermore, the author draws on his expertise in machine learning and FPGA programming to make progress on a very different problem, namely the real-time image analysis of optical coherence tomography for atherosclerotic arteries.
