1. 1-24 of 44 1 2 »
    1. The potential of optical coherence tomography for diagnosing meniscal pathology

      The potential of optical coherence tomography for diagnosing meniscal pathology
      Meniscal tears are often associated with anterior cruciate ligament (ACL) injury and may lead to pain and discomfort in humans. Maximal preservation of meniscal tissue is highly desirable to mitigate the progression of osteoarthritis. Guidelines of which meniscal tears are amenable to repair and what part of damaged tissues should be removed are elusive and lacking consensus. Images of microstructural changes in meniscus would potentially guide the surgeons to manage the meniscal tears better, but the resolution of current diagnostic techniques is limited for this application. In this study, we demonstrated the feasibility of using optical coherence tomography (OCT) for ...
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    2. Resonant acoustic spectroscopy of soft tissues using embedded magnetomotive nanotransducers and optical coherence tomography

      Resonant acoustic spectroscopy of soft tissues using embedded magnetomotive nanotransducers and optical coherence tomography
      We present a new method for performing dynamic elastography of soft tissue samples. By sensing nanoscale displacements with optical coherence tomography, a chirped, modulated force is applied to acquire the mechanical spectrum of a tissue sample within a few seconds. This modulated force is applied via magnetic nanoparticles, named 'nanotransducers', which are diffused into the tissue, and which contribute negligible inertia to the soft tissue mechanical system. Using this novel system, we observed that excised tissues exhibit mechanical resonance modes which are well described by a linear damped harmonic oscillator. Results are validated by using cylindrical tissue phantoms of agarose ...
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    3. In vivo endoscopic multi-beam optical coherence tomography

      In vivo endoscopic multi-beam optical coherence tomography
      multichannel optical coherence tomography (multi-beam OCT) system and an in vivo endoscopic imaging probe were developed using a swept-source OCT system. The distal optics were micro-machined to produce a high numerical aperture, multi-focus fibre optic array. This combination resulted in a transverse design resolution of <10 µm full width half maximum (FWHM) throughout the entire imaging range, while also increasing the signal intensity within the focus of the individual channels. The system was used in a pre-clinical rabbit study to acquire in vivo structural images of the colon and ex vivo images of the oesophagus and trachea. A good correlation ...
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    4. Full-field optical coherence tomography for the rapid estimation of epidermal thickness: study of patients with diabetes mellitus type 1

      Changes in morphology of the skin are an important factor that can affect non-invasive measurements performed through this organ, in particular for glucose monitoring in e.g. patients with diabetes mellitus. A characterization technique for non-contact in vivo profiling of the superficial skin layers can be beneficial for evaluation of the performance of such measurement systems. We applied a full-field optical coherence tomography (OCT) system followed by the fully automatic processing for this task. With the developed procedure, non-invasive quantification of the skin morphology can be performed within a few minutes. The dorsal skin of the upper arm of 22 ...
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    5. Co-registered optical coherence tomography and fluorescence molecular imaging for simultaneous morphological and molecular imaging

      Abstract. Optical coherence tomography (OCT) provides high-resolution, cross-sectional imaging of tissue microstructure in situ and in real time, while fluorescence molecular imaging (FMI) enables the visualization of basic molecular processes. There is a great deal of interest in combining these two modalities so that the tissue's structural and molecular information can be obtained simultaneously. This could greatly benefit biomedical applications such as detecting early diseases and monitoring therapeutic interventions. In this research, an optical system that combines OCT and FMI was developed. The system demonstrated that it could co-register en face OCT and FMI images with a 2.4 ...
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    6. Platinum microheater integrated silicon optical bench assembly for endoscopic optical coherence tomography

      Platinum microheater integrated silicon optical bench assembly for endoscopic optical coherence tomography
      A novel platinum microheater and comb isolator integrated silicon optical bench (SiOB) assembly method has been successfully demonstrated to provide electrical connection and high precision alignment for a two-axis gimbal-less micromirror. Localized heating and wetting of plastic core micro solder balls is achieved by the integrated platinum heater, and the maximum measured temperature of the platinum heater is about 250 °C. In addition, assembly procedures are significantly simplified by involving a comb isolator made by deep reactive ion etching (DRIE) in comparison with our previously reported design. DRIE is also applied to form a 45° trench on the lower silicon ...
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    7. Quantification of the optical surface reflection and surface roughness of articular cartilage using optical coherence tomography

      Optical coherence tomography (OCT) is a promising new technique for characterizing the structural changes of articular cartilage in osteoarthritis (OA). The calculation of quantitative parameters from the OCT signal is an important step to develop OCT as an effective diagnostic technique. In this study, two novel parameters for the quantification of optical surface reflection and surface roughness from OCT measurements are introduced: optical surface reflection coefficient (ORC), describing the amount of a ratio of the optical reflection from cartilage surface with respect to that from a reference material, and OCT roughness index (ORI) indicating the smoothness of the cartilage surface ...
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    8. Evaluation of a cheap ultrasonic stage for light source coherence function measurement, optical coherence tomography and dynamic focusing

      We evaluate the performance of a cheap ultrasonic stage in setups related to optical coherence tomography. The stage was used in several configurations: (1) optical delay line in an optical coherence tomography (OCT) setup; (2) as a delay line measuring coherence function of a low coherence source (e.g. superluminescent diode) and (3) in a dynamic focusing arrangement. The results are as follows: the stage is suitable for coherence function measurement (coherence length up to 70 µm) of the light source and dynamic focusing. We found it unsuitable for OCT due to an unstable velocity profile. Despite this, the velocity ...
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    9. Piezoelectric scanning mirrors for endoscopic optical coherence tomography

      A novel piezoelectric scanning mirror design for endoscopic optical coherence tomography (OCT) is presented. OCT is an interferometric technique providing microscopic tomographic sectioning of biological samples with mm-range penetration capability in tissue and is suited for integration with endoscopes using fiber-based light delivery to the sample. The piezoelectric scanning mirror was designed to provide wide-range rapid forwarding-looking scanning of the optical beam at the distal end of a compact catheter. The optical scanner provides a large ratio of mirror aperture to device size with rectangular mirror sizes ranging from 600 µm × 840 µm to 840 µm × 1600 µm. Static angular ...
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    10. Characteristics of time-domain optical coherence tomography profiles generated from blood–saline mixtures

      Abstract. Time-domain optical coherence tomography (OCT) employing a 1300 nm broadband source is used to study flowing blood–saline mixtures with blood concentration ranging from 20% to 100%. The study emphasizes the characteristics of the recorded OCT signal and its connection with the properties of the corresponding fluids. There are three regions with distinct properties along the compounded OCT profiles showing the signal dependence on depth. The recorded OCT signal increases for the first 80 µm into the fluid. The flow characteristics of the solution and the average spatial orientation of the blood cells can be extracted from this region ...
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    11. Swept source optical coherence tomography for radiation-enhanced hepatocellular carcinoma cell invasion imaging

      Abstract. In this study, we evaluated the effectiveness of using swept-source optical coherence tomography (SS-OCT) to monitor the enhancement of hepatocellular carcinoma (HCC) cell invasiveness by radiation. SS-OCT images were acquired and recorded to obtain three-dimensional datasets at discrete time points of 12, 24 and 48 h after irradiating HepG2 cells with 7.5 Gy. The cell migration distance in three-dimensional tissue models was quantified from images of radiation-induced and sham-irradiated cells, and this method was compared with the conventional Boyden chamber assay conducted at the same time points. SS-OCT measurements show that most cells were found near the gel ...
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    12. Swept source optical coherence tomography for radiation-enhanced hepatocellular carcinoma cell invasion imaging

      Abstract. In this study, we evaluated the effectiveness of using swept-source optical coherence tomography (SS-OCT) to monitor the enhancement of hepatocellular carcinoma (HCC) cell invasiveness by radiation. SS-OCT images were acquired and recorded to obtain three-dimensional datasets at discrete time points of 12, 24 and 48 h after irradiating HepG2 cells with 7.5 Gy. The cell migration distance in three-dimensional tissue models was quantified from images of radiation-induced and sham-irradiated cells, and this method was compared with the conventional Boyden chamber assay conducted at the same time points. SS-OCT measurements show that most cells were found near the gel ...
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    13. Evaluation of patient suitability for a retinal prosthesis using structural and functional tests of inner retinal integrity

      Evaluation of patient suitability for a retinal prosthesis using structural and functional tests of inner retinal integrity
      Abstract. The purpose of this study was to assess inner retinal structure and function in patients with retinitis pigmentosa (RP) using optical coherence tomography (OCT) imaging of the retina, and electrical stimulation of the retina with a contact lens electrode. OCT images of 17 RP patients were acquired at the macula and at four quadrants of the peripheral retina in both eyes. Analysis was made of the residual inner retinal thickness and nerve fibre layer thickness in RP patients, and this was compared to normal controls. Eight of these patients further underwent contact lens electrical stimulation of one eye and ...
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    14. The electromagnetic response of human skin in the millimetre and submillimetre wave range

      Recent studies of the minute morphology of the skin by optical coherence tomography revealed that the sweat ducts in human skin are helically shaped tubes, filled with a conductive aqueous solution. This, together with the fact that the dielectric permittivity of the dermis is higher than that of the epidermis, brings forward the supposition that as electromagnetic entities, the sweat ducts could be regarded as low Q helical antennas. The implications of this statement were further investigated by electromagnetic simulation and experiment of the in vivo reflectivity of the skin of subjects under varying physiological conditions (Feldman et al 2008 ...
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    15. Audio frequency in vivo optical coherence elastography

      Abstract. We present a new approach to optical coherence elastography (OCE), which probes the local elastic properties of tissue by using optical coherence tomography to measure the effect of an applied stimulus in the audio frequency range. We describe the approach, based on analysis of the Bessel frequency spectrum of the interferometric signal detected from scatterers undergoing periodic motion in response to an applied stimulus. We present quantitative results of sub-micron excitation at 820 Hz in a layered phantom and the first such measurements in human skin in vivo. General scientific summary. We present a novel optical coherence elastography technique ...
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    16. A p-type-doped quantum dot superluminescent LED with broadband and flat-topped emission spectra obtained by post-growth intermixing under a GaAs proximity cap

      A p-type-doped quantum dot superluminescent LED with broadband and flat-topped emission spectra obtained by post-growth intermixing under a GaAs proximity cap
      Broadband superluminescent light emitting diodes are realized by a post-growth annealing process, on modulation p-doped multiple InAs/InGaAs/GaAs quantum dot layer structures, under a GaAs proximity cap. The device exhibits a large and flat emission with spectral width up to 132 nm at 2 mW. This is mainly attributed to the reduction of the energy separation between the ground state and the excited state, in addition to the optical quality of the intermixed modulation p-doped quantum dot materials being comparable to that of the as-grown sample
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    17. Simultaneous tomography and topography of silicon integrated circuits using full-fieldswept-source optical coherence tomography

      Abstract. We demonstrate simultaneous tomography and topography of micro-electro-mechanical systems based on silicon integrated circuits using full-field swept-source optical coherence tomography. The optical set-up consists of a swept-source system, a compact Michelson interferometer, and an area detector. The swept-source system comprises a superluminescent diode as a broadband light source in conjunction with an acousto-optic tunable filter as a fast frequency tuning device. By means of sweeping the frequency of the light source, multiple interferograms were recorded and both the amplitude and the phase map of the interference fringe signal were reconstructed. Optically sectioned images of the silicon integrated circuits were ...
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    18. Multiple interference and spatial frequencies' effect on the application of frequency-domain optical coherence tomography to thin films' metrology

      Abstract. Frequency-domain optical coherence tomography (FD-OCT) was proved to be very useful under two conditions: (i) the layered sample scatters so that multiple interferences do not exist and (ii) the interferometer uses collimated beams so that a single spatial frequency is used. We examine the use of FD-OCT for thin films' metrology when multiple interferences and a range of spatial frequencies exist, such as with interference microscopy where the spatial frequencies' content is provided by the numerical aperture (NA) of the microscope objectives. The effect of multiple interferences is found to be reduced significantly by shortening the coherence length such ...
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    19. An optical coherence tomography (OCT)-based air jet indentation system for measuring the mechanical properties of soft tissues

      Abstract. A novel noncontact indentation system with the combination of an air jet and optical coherence tomography (OCT) was presented in this paper for the quantitative measurement of the mechanical properties of soft tissues. The key idea of this method is to use a pressure-controlled air jet as an indenter to compress the soft tissue in a noncontact way and utilize the OCT signals to extract the deformation induced. This indentation system provides measurement and mapping of tissue elasticity for small specimens with high scanning speed. Experiments were performed on 27 silicone tissue-mimicking phantoms with different Young's moduli, which ...
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    20. Optical and terahertz measurement techniques for flat-faced pharmaceutical tablets: a case study of gloss, surface roughness and bulk properties of starch acetate tablets

      Abstract. Surface and bulk properties of flat-faced starch acetate tablets were studied. For surface quality inspection optical coherence tomography and recently developed diffractive glossmeter were utilized. Both these optical devices together provide local information on surface roughness and gloss of a tablet over a measured area. The concepts of mean topography and mean gloss profile for surface quality of a tablet are introduced. It was observed that the surface quality of the tablet varies, and compression at high pressure may not guarantee a good surface quality of the tablet. Using novel statistical parameters for gloss and relevant surface roughness parameter ...
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    21. Potential ability of hematoporphyrin to enhance an optical coherence tomographic image of gastric cancer in vivo in mice

      Abstract. An ideal diagnostic system for the tumor tissues should be able to detect and define the location of tumor tissues and the early development of malignant diseases. There is great need for enhancement of imaging ability to tumor tissues. Optical coherence tomography (OCT) is used in detection and location of varied tumor tissues. In order to improve the sensitivity and specificity of an OCT image, hematoporphyrin as a new type of contrast agent was used in this study. The orthotopic graft model of gastric cancer in nude mice was used. The image formations of the tumor tissues without and ...

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    22. Design and development of a 3D scanning Mems Oct probe using a novel SiOB package assembly

      Design and development of a 3D scanning Mems Oct probe using a novel SiOB package assembly
      Abstract. A MEMS optical coherence tomography (OCT) probe prototype was developed using a unique assembly based on silicon optical bench (SiOB) methodology. The probe is formed by integrating a three-dimensional (3D) scanning micromirror, gradient refractive index (GRIN) lens and optical fiber on SiOB substrates having prefabricated self-aligned slots. The two-axis scanning micromirror is based on electrothermal actuation with required voltage less than 2 V for mechanical deflections up to 17°. The optical probe was enclosed within a biocompatible, transparent and waterproof polycarbonate tube with a view of in vivo diagnostic applications. The diameter of the miniature probe is less than ...
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    23. A model of speckle contrast in optical coherence tomography for characterizing the scattering coefficient of homogenous tissues

      Abstract. We present a theoretical model for analyzing the speckle contrast of optical coherence tomography (OCT). This model is based on the addition of noise and an OCT signal in the logarithmic scale. The theoretical model reveals that, for the superficial layer of homogenous tissue, the contrast ratio is a linear function of the location of the coherence gate in the sample and the slope of this linear dependence is proportional to the scattering coefficient. The theoretical model is consistent with the experimental results, suggesting that the slope can be useful to characterize the scattering coefficient of the homogenous samples.

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    24. Changes in wall motion and blood flow in the outflow tract of chick embryonic hearts observed with optical coherence tomography after outflow tract banding and vitelline-vein ligation

      Author(s): Sandra Rugonyi, Carley Shaut, Aiping Liu, Kent Thornburg and Ruikang K Wang. Affiliation(s): Division of Biomedical Engineering, Oregon Health & Science University, 3303 SW Bond Ave., CH13B, Portland, OR 97239, USA; Heart Research Center, Oregon Health & Science University, Portland, OR, USA
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    1-24 of 44 1 2 »
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