1. 1-24 of 116 1 2 3 4 5 »
    1. Chromatic dispersion effects in ultra-low coherence interferometry

      Chromatic dispersion effects in ultra-low coherence interferometry

      We consider the properties of an interference signal shift from zero-path-difference position in the presence of an uncompensated dispersive layer in one of the interferometer arms. It is experimentally shown that in using an ultra-low coherence light source, the formation of the interference signal is also determined by the group velocity dispersion, which results in a nonlinear dependence of the position of the interference signal on the geometrical thickness of the dispersive layer. The discrepancy in the dispersive layer and compensator refractive indices in the third decimal place is experimentally shown to lead to an interference signal shift that is ...

      Read Full Article
    2. Laser-ablated silicon nanoparticles: optical properties and perspectives in optical coherencetomography

      Laser-ablated silicon nanoparticles: optical properties and perspectives in optical coherencetomography

      Due to their biocompatibility silicon nanoparticles have high potential in biomedical applications, especially in optical diagnostics. In this paper we analyze properties of the silicon nanoparticles formed via laser ablation in water and study the possibility of their application as contrasting agents in optical coherence tomography (OCT). The nanoparticles suspension was produced by picosecond laser irradiation of monocrystalline silicon wafers in water. According to transmission electron microcopy analysis the silicon nanoparticles in the obtained suspension vary in size from 2 to 200?nm while concentration of the particles is estimated as 10 13 cm ?3 . The optical properties of the ...

      Read Full Article
    3. In vivo volumetric depth-resolved vasculature imaging of human limbus and sclera with 1μm swept source phase-variance optical coherence angiography

      In vivo volumetric depth-resolved vasculature imaging of human limbus and sclera with 1μm swept source phase-variance optical coherence angiography

      We present in vivo volumetric depth-resolved vasculature images of the anterior segment of the human eye acquired with phase-variance based motion contrast using a high-speed (100 kHz, 10 5 A-scans/s) swept source optical coherence tomography system (SSOCT). High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. The human corneo–scleral junction and sclera were imaged with swept source phase-variance optical coherence angiography and compared with slit lamp images from the same eyes of normal subjects. Different features of the rich vascular system in the conjunctiva and episclera were visualized and described. This system ...

      Read Full Article
    4. Effect of fibrinogen on blood coagulation detected by optical coherence tomography

      Effect of fibrinogen on blood coagulation detected by optical coherence tomography

      Our previous work demonstrated that an optical coherence tomography (OCT) technique and the parameter 1/ e light penetration depth ( d 1/ e ) were able to characterize the whole blood coagulation process in contrast to existing optical tests that are performed on plasma samples. To evaluate the feasibility of the technique for quantifying the effect of fibrinogen (Fbg) on blood coagulation, a dynamic study of d 1/ e of blood in various Fbg concentrations was performed in static state. Two groups of blood samples of hematocrit (HCT) in 35, 45, and 55% were reconstituted of red blood cells with: 1) treated ...

      Read Full Article
    5. Functional optical coherence tomography: principles and progress

      Functional optical coherence tomography: principles and progress

      In the past decade, several functional extensions of optical coherence tomography (OCT) have emerged, and this review highlights key advances in instrumentation, theoretical analysis, signal processing and clinical application of these extensions. We review five principal extensions: Doppler OCT (DOCT), polarization-sensitive OCT (PS-OCT), optical coherence elastography (OCE), spectroscopic OCT (SOCT), and molecular imaging OCT. The former three have been further developed with studies in both ex vivo and in vivo human tissues. This review emphasizes the newer techniques of SOCT and molecular imaging OCT, which show excellent potential for clinical application but have yet to be well reviewed in the ...

      Read Full Article
    6. An efficient phase analysis-based wavenumber linearization scheme for swept source optical coherence tomography systems

      An efficient phase analysis-based wavenumber linearization scheme for swept source optical coherence tomography systems

      This letter reports an efficient phase analysis-based direct time domain resampling scheme for swept source-based optical coherence tomography (SS-OCT) systems. The unwrapped phase values, representing non-linear frequency sweeping of the laser, are extracted from the calibration signal generated by a Mach–Zehnder interferometer. Equidistant wavenumber spaces are calculated by normalizing obtained phase values followed by scaling to the maximum number of sampling points. The non-uniform fractional time index values corresponding to the uniformly distributed phase values are computed directly from the linearizer coordinates in order to eliminate the use of the polynomial fitting approach that is used in existing phase-based ...

      Read Full Article
    7. Optical Coherence Tomography Velocimetry with Complex Fluids

      Optical Coherence Tomography Velocimetry with Complex Fluids

      We present recent results obtained with an Optical Coherence Tomography Velocimetry technique. An optical interferometer measures the velocity of a sheared fluid at specific depths of the sample using the coherence length of the light source. The technique allows the dynamics of 3 pico liter volumes to be probed inside opaque complex fluids. In a study of opaque starch suspensions, classical bulk rheology experiments show non-linear shear thickening, whereas observations of the velocity profiles as a function of distance across the gap show Newtonian behavior. The ability of the technique to measure velocity fluctuations is also discussed for the case ...

      Read Full Article
    8. Imaging of spectral-domain optical coherence tomography using a superluminescent diode based on InAs quantum dots emitting broadband spectrum with Gaussian-like shape

      Imaging of spectral-domain optical coherence tomography using a superluminescent diode based on InAs quantum dots emitting broadband spectrum with Gaussian-like shape

      We developed a low-coherence light source based on self-assembled InAs quantum dots (QDs) with controlled emission wavelengths and applied it to optical coherence tomography (OCT) imaging. A current-driven superluminescent diode (SLD) light source including four layers of QDs exhibits a broadband (80-nm-bandwidth) emission centered at approximately 1.2 µm with a Gaussian-like spectral shape at room temperature. Spectral-domain OCT (SD-OCT) using the QD-SLD as a light source was developed and imaging with the SD-OCT was demonstrated. The axial resolution was estimated to be approximately 8 µm in air and no apparent side lobes appeared beside the point spread function, indicating ...

      Read Full Article
    9. Modifications of intensity-interferometric spectral-domain optical coherence tomography withdispersion cancellation

      Modifications of intensity-interferometric spectral-domain optical coherence tomography withdispersion cancellation

      Intensity-interferometric spectral-domain (SD) optical coherence tomography (OCT) developed recently enables axial-scan-free cross-sectional imaging with group-velocity dispersion cancellation and a factor-of- resolution improvement. This paper is concerned with a simple and practical method of realizing OCT of this kind. Specifically, we demonstrate theoretically and experimentally that intensity-interferometric SD-OCT can be realized in a simple way by means of a slightly modified conventional SD-OCT setup.

      Read Full Article
    10. Parametric imaging of viscoelasticity using optical coherence elastography

      Parametric imaging of viscoelasticity using optical coherence elastography

      We demonstrate imaging of soft tissue viscoelasticity using optical coherence elastography. Viscoelastic creep deformation is induced in tissue using step-like compressive loading and the resulting time-varying deformation is measured using phase-sensitive optical coherence tomography. From a series of co-located B-scans, we estimate the local strain rate as a function of time, and parameterize it using a four-parameter Kelvin–Voigt model of viscoelastic creep. The estimated viscoelastic strain and time constant are used to visualize viscoelastic creep in 2D, dual-parameter viscoelastograms. We demonstrate our technique on six silicone tissue-simulating phantoms spanning a range of viscoelastic parameters. As an example in soft ...

      Read Full Article
    11. Automated pharmaceutical tablet coating layer evaluation of optical coherence tomography images

      Automated pharmaceutical tablet coating layer evaluation of optical coherence tomography images

      Film coating of pharmaceutical tablets is often applied to influence the drug release behaviour. The coating characteristics such as thickness and uniformity are critical quality parameters, which need to be precisely controlled. Optical coherence tomography (OCT) shows not only high potential for off-line quality control of film-coated tablets but also for in-line monitoring of coating processes. However, an in-line quality control tool must be able to determine coating thickness measurements automatically and in real-time. This study proposes an automatic thickness evaluation algorithm for bi-convex tables, which provides about 1000 thickness measurements within 1 s. Beside the segmentation of the coating ...

      Read Full Article
    12. Development of novel high-speed en face optical coherence tomography system using KTN optical beamdeflector

      Development of novel high-speed en face optical coherence tomography system using KTN optical beamdeflector

      We developed a novel high-speed en face optical coherence tomography (OCT) system using a KTa 1– x Nb x O 3 (KTN) optical beam deflector. Using the imaging system, fast scanning was performed at 200 kHz by the KTN beam deflector, while slow scanning was performed at 400 Hz by the galvanometer mirror. In a preliminary experiment, we obtained en face OCT images of a human fingerprint at 400 fps. This is the highest speed reported in time-domain en face OCT imaging and is comparable to the speed of swept-source OCT. A 3D-OCT image of a sweat gland was also ...

      Read Full Article
    13. Influence of nanoparticles accumulation on optical properties of human normal and cancerous liver tissue in vitro estimated by OCT

      Influence of nanoparticles accumulation on optical properties of human normal and cancerous liver tissue in vitro estimated by OCT

      In this work, the potential use of nanoparticles as contrast agents by using spectral domain optical coherence tomography (SD-OCT) in liver tissue was demonstrated. Gold nanoparticles (average size of 25 and 70 nm), were studied in human normal and cancerous liver tissues in vitro , respectively. Each sample was monitored with SD-OCT functional imaging for 240 min. Continuous OCT monitoring showed that, after application of gold nanoparticles, the OCT signal intensities of normal liver and cancerous liver tissue both increase with time, and the larger nanoparticles tend to produce a greater signal enhancement in the same type of tissue. The results ...

      Read Full Article
    14. Monitoring of permeability of different analytes in human normal and cancerous bladder tissues invitro using optical coherence tomography

      Monitoring of permeability of different analytes in human normal and cancerous bladder tissues invitro using optical coherence tomography

      We report our preliminary results on quantification of glucose and dimethyl sulfoxide (DMSO) diffusion in normal and cancerous human bladder tissues in vitro by using a spectral domain optical coherence tomography (SD-OCT). The permeability coefficients (PCs) of a 30% aqueous solution of glucose are found to be (7.92 ± 0.81) × 10 -6 cm s -1 and (1.19 ± 0.13) × 10 -5 cm s -1 in normal and cancerous bladder tissues, respectively. The PCs of 50% DMSO are calculated to be (8.99 ± 0.93) × 10 -6 cm s -1 and (1.43 ± 0.17) × 10 -5 cm s ...

      Read Full Article
    15. Assessment of laser-induced acceleration effects in optical clearing of in vivo human skin by optical coherence tomography

      Assessment of laser-induced acceleration effects in optical clearing of in vivo human skin by optical coherence tomography

      Laser irradiation is considered to be a promising innovative technology which has been developed in an attempt to increase transdermal drug delivery. In this study, a near-infrared CW diode laser (785 nm) was applied to increase permeability of glycerol solutions in human skin in vivo and improve the optical clearing efficacy. Results show that for both 15%v/v and 30%v/v glycerol, the permeability coefficient increased significantly if the detected area of the skin tissue was treated with laser irradiation before optical clearing agents (OCAs) were applied. This study based on optical coherence tomography imaging technique and optical ...

      Read Full Article
    16. Supercontinuum generation for ultrahigh-resolution optical coherence tomography at wavelength of 0.8µm using carbon nanotube fiber laser and similariton amplifier

      Supercontinuum generation for ultrahigh-resolution optical coherence tomography at wavelength of 0.8µm using carbon nanotube fiber laser and similariton amplifier

      We demonstrated supercontinuum (SC) generation for ultrahigh-resolution optical coherence tomography (UHR-OCT) in the 0.8 µm wavelength region using an ultrashort-pulse fiber laser system. An Er-doped ultrashort-pulse fiber laser with single-wall carbon nanotubes was developed as the seed pulse source. A 46 fs, highest quality, pedestal-free, clean, ultrashort pulse was generated with a similariton amplifier. Then, a 60 fs ideal ultrashort pulse was generated at a wavelength of 0.8 µm with a second-harmonic generation (SHG) crystal, and a Gaussian-like SC was generated in a photonic crystal fiber. UHR-OCT was demonstrated using the generated SC, and precise images of a ...

      Read Full Article
    17. Anisotropic polyvinyl alcohol hydrogel phantom for shear wave elastography in fibrous biological soft tissue: a multimodality characterization

      Anisotropic polyvinyl alcohol hydrogel phantom for shear wave elastography in fibrous biological soft tissue: a multimodality characterization

      Shear wave elastography imaging techniques provide quantitative measurement of soft tissues elastic properties. Tendons, muscles and cerebral tissues are composed of fibers, which induce a strong anisotropic effect on the mechanical behavior. Currently, these tissues cannot be accurately represented by existing elastography phantoms. Recently, a novel approach for orthotropic hydrogel mimicking soft tissues has been developed (Millon et al 2006 J. Biomed. Mater. Res. B 305–11). The mechanical anisotropy is induced in a polyvinyl alcohol (PVA) cryogel by stretching the physical crosslinks of the polymeric chains while undergoing freeze/thaw cycles. In the present study we propose an original ...

      Read Full Article
    18. Simultaneous estimation of bidirectional particle flow and relative flux using MUSIC-OCT: phantom studies

      Simultaneous estimation of bidirectional particle flow and relative flux using MUSIC-OCT: phantom studies

      In an optical coherence tomography (OCT) scan from a living tissue, red blood cells (RBCs) are the major source of backscattering signal from moving particles within microcirculatory system. Measuring the concentration and velocity of RBC particles allows assessment of RBC flux and flow, respectively, to assess tissue perfusion and oxygen/nutrition exchange rates within micro-structures. In this paper, we propose utilizing spectral estimation techniques to simultaneously quantify bi-directional particle flow and relative flux by spectral estimation of the received OCT signal from moving particles within capillary tubes embedded in tissue mimicking phantoms. The proposed method can be directly utilized for ...

      Read Full Article
    19. Dependence of light attenuation and backscattering on collagen concentration and chondrocyte densityin agarose scaffolds

      Dependence of light attenuation and backscattering on collagen concentration and chondrocyte densityin agarose scaffolds

      Optical coherence tomography (OCT) has been applied for high resolution imaging of articular cartilage. However, the contribution of individual structural elements of cartilage on OCT signal has not been thoroughly studied. We hypothesize that both collagen and chondrocytes, essential structural components of cartilage, act as important light scatterers and that variation in their concentrations can be detected by OCT through changes in backscattering and attenuation. To evaluate this hypothesis, we established a controlled model system using agarose scaffolds embedded with variable collagen concentrations and chondrocyte densities. Using OCT, we measured the backscattering coefficient ( µ b ) and total attenuation coefficient ( µ t ) in ...

      Read Full Article
    20. Influence of different sized nanoparticles combined with ultrasound on the optical properties of invitro normal and cancerous human lung tissue studied with OCT and diffuse reflectance spectra

      Influence of different sized nanoparticles combined with ultrasound on the optical properties of invitro normal and cancerous human lung tissue studied with OCT and diffuse reflectance spectra

      The present study is concerned with the in vitro study of different sized titanium dioxide (TiO 2 ) nanoparticles' (NPs) penetration and accumulation in human normal lung (NL) tissue and lung adenocarcinoma tumor (LAT) tissue by the methods of continuous optical coherence tomography (OCT) monitoring and diffuse reflectance (DR) spectra measurement, and their evaluating the effects of TiO 2 NPs in two sizes (60 nm and 100 nm) and their combination with ultrasound (US) on the optical properties of human NL and LAT tissue. Spectral measurements indicate that TiO 2 NPs penetrate and accumulate into the tissues and thus induce enhancement ...

      Read Full Article
    21. MOEMS optical delay line for optical coherence tomography

      MOEMS optical delay line for optical coherence tomography

      Micro-Opto-Electro-Mechanical optical coherence tomography, a lab-on-chip for biomedical applications is designed, studied, fabricated and characterized. To fabricate the device standard PolyMUMPS processes is adopted. We report the utilization of electro-optic modulator for a fast scanning optical delay line for time domain optical coherence tomography. Design optimization are performed using Tanner EDA while simulations are performed using COMSOL. The paper summarizes various results and fabrication methodology adopted. The success of the device promises a future hand-held or endoscopic optical coherence tomography for biomedical applications.

      Read Full Article
    22. Measurement of the temperature dependence of Young's modulus of cartilage by phase-sensitive optical coherence elastograph

      Measurement of the temperature dependence of Young's modulus of cartilage by phase-sensitive optical coherence elastograph

      The development of an effective system to monitor the changes in the elastic properties of cartilage tissue with increasing temperature in laser reconstruction is an urgent practical task. In this paper, the use of phase-sensitive optical coherence elastography for detection of elastic waves in the sample has allowed Young's modulus of cartilage tissue to be measured directly during heating. Young's modulus was calculated from the group velocity of propagation of elastic waves excited by means of a system supplying focused air pulses. The measurement results are in agreement with the results of measurements of the modulus of elasticity ...

      Read Full Article
    23. Improvement of lateral resolution of spectral domain optical coherence tomography images inout-of-focus regions with holographic data processing techniques

      Improvement of lateral resolution of spectral domain optical coherence tomography images inout-of-focus regions with holographic data processing techniques

      An analogy between spectral-domain optical coherence tomography (SD OCT) data and broadband digital holography data is considered. Based on this analogy, a method for processing SD OCT data, which makes it possible to construct images with a lateral resolution in the whole investigated volume equal to the resolution in the in-focus region, is developed. Several issues concerning practical application of the proposed method are discussed.

      Read Full Article
    24. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

      Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

      We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-μm high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with ...

      Read Full Article
    1-24 of 116 1 2 3 4 5 »
  1. Categories

    1. Applications:

      Art, Cardiology, Dentistry, Dermatology, Developmental Biology, Gastroenterology, Gynecology, Microscopy, NDE/NDT, Neurology, Oncology, Ophthalmology, Other Non-Medical, Otolaryngology, Pulmonology, Urology
    2. Business News:

      Acquisition, Clinical Trials, Funding, Other Business News, Partnership, Patents
    3. Technology:

      Broadband Sources, Probes, Tunable Sources
    4. Miscellaneous:

      Jobs & Studentships, Student Theses, Textbooks