1. 1-24 of 146 1 2 3 4 5 6 »
    1. Simple model to simulate OCT-depth signal in weakly and strongly scattering homogeneous media

      Simple model to simulate OCT-depth signal in weakly and strongly scattering homogeneous media

      We present a simple and efficient Monte Carlo model to predict the scattering coefficients and the influence of multiple photon scattering with increasing concentration of scattering centers from optical coherence tomography (OCT) data. While the model reliably estimates optical sample parameters for a broad range of concentrations, it does not require inclusion of more complex phenomena such as dependent scattering. Instead, it relies on a particular weighting function which is introduced to describe various orders of multiple scattering events. In weakly scattering homogeneous media the measured scattering coefficient depends linearly on the concentration of scattering centers. In the case of ...

      Read Full Article
    2. Optical coherence tomography for visualizing transient strains and measuring large deformations in laser-induced tissue reshaping

      Optical coherence tomography for visualizing transient strains and measuring large deformations in laser-induced tissue reshaping

      In the context of the development of emerging laser-assisted thermo-mechanical technologies for non-destructive reshaping of avascular collagenous tissues (cartilages and cornea), we report the first application of phase-sensitive optical coherence tomography (OCT) for visualizing transient strains involving supra-wavelength inter-frame displacements of scatterers. Usually phase-sensitive OCT assumes the visualization of sub-pixel and even sub-wavelength displacements of scatterers and fairly small strains (say, <10 −3 ), which conventionally implies the necessity of averaging for enhancing the effective signal-to-noise ratio and, correspondingly, the application of small-amplitude actuators producing periodic deformations. The original approach used here allows for direct estimation of elevated strains ~10 −2 ...

      Read Full Article
    3. Spectral phase-based automatic calibration scheme for swept source-based optical coherence tomography systems

      Spectral phase-based automatic calibration scheme for swept source-based optical coherence tomography systems

      The automatic calibration in Fourier-domain optical coherence tomography (FD-OCT) systems allows for high resolution imaging with precise depth ranging functionality in many complex imaging scenarios, such as microsurgery. However, the accuracy and speed of the existing automatic schemes are limited due to the functional approximations and iterative operations used in their procedures. In this paper, we present a new real-time automatic calibration scheme for swept source-based optical coherence tomography (SS-OCT) systems. The proposed automatic calibration can be performed during scanning operation and does not require an auxiliary interferometer for calibration signal generation and an additional channel for its acquisition. The ...

      Read Full Article
    4. Depth-resolved 3D visualization of coronary microvasculature with optical microangiography

      Depth-resolved 3D visualization of coronary microvasculature with optical microangiography

      In this study, we propose a novel implementation of optical coherence tomography-based angiography combined with ex vivo perfusion of fixed hearts to visualize coronary microvascular structure and function. The extracorporeal perfusion of Intralipid solution allows depth-resolved angiographic imaging, control of perfusion pressure, and high-resolution optical microangiography. The imaging technique offers new opportunities for microcirculation research in the heart, which has been challenging due to motion artifacts and the lack of independent control of pressure and flow. With the ability to precisely quantify structural and functional features, this imaging platform has broad potential for the study of the pathophysiology of microvasculature ...

      Read Full Article
    5. Wideband ultrafast fiber laser sources for OCT and metrology

      Wideband ultrafast fiber laser sources for OCT and metrology

      Fiber lasers, which use optical fibers as ideal waveguides, have been attracting a great deal of attention as stable, practical, and maintenance-free lasers. Using a combination of an ultrashort-pulse fiber laser and a nonlinear fiber, we can realize wideband highly functional ultrafast fiber laser sources. The generation of ultrashort pulses with wide wavelength tunability and supercontinua based on fiber lasers and nonlinear fibers has been demonstrated. These techniques are useful for laser applications, especially for imaging and metrology. In this topical review, the fundamentals of and recent progress in wideband ultrafast fiber laser sources and their applications are reviewed mainly ...

      Read Full Article
    6. Gold nanorods with higher aspect ratio as potential contrast agent in optical coherence tomography and for photothermal applications around 1300 nm imaging window

      Gold nanorods with higher aspect ratio as potential contrast agent in optical coherence tomography and for photothermal applications around 1300 nm imaging window

      Over the past few years, plasmon-resonant nanorods of gold (AuNRs) have been used as the contrast agent in optical imaging and for photothermal applications. However, most of these studies were limited to AuNRs whose spectral peaks fall below 1000 nm. Recently, optical coherence tomography (OCT) imaging around 1300 nm has become one of the niche research areas due to its potential for many diagnostics imaging applications. In this paper, we have investigated plasmon-resonant AuNRs with higher aspect ratio as a potential contrast agent in OCT and for photothermal applications around the 1300 nm window. The AuNRs with an aspect ratio ...

      Read Full Article
    7. Detection of extracellular matrix modification in cancer models with inverse spectroscopic optical coherence tomography

      Detection of extracellular matrix modification in cancer models with inverse spectroscopic optical coherence tomography

      In cancer biology, there has been a recent effort to understand tumor formation in the context of the tissue microenvironment. In particular, recent progress has explored the mechanisms behind how changes in the cell-extracellular matrix ensemble influence progression of the disease. The extensive use of in vitro tissue culture models in simulant matrix has proven effective at studying such interactions, but modalities for non-invasively quantifying aspects of these systems are scant. We present the novel application of an imaging technique, Inverse Spectroscopic Optical Coherence Tomography, for the non-destructive measurement of in vitro biological samples during matrix remodeling. Our findings indicate ...

      Read Full Article
    8. A 45° saw-dicing process applied to a glass substrate for wafer-level optical splitter fabrication for optical coherence tomography

      A 45° saw-dicing process applied to a glass substrate for wafer-level optical splitter fabrication for optical coherence tomography

      This paper reports on the development of a technology for the wafer-level fabrication of an optical Michelson interferometer, which is an essential component in a micro opto-electromechanical system (MOEMS) for a miniaturized optical coherence tomography (OCT) system. The MOEMS consists on a titanium dioxide/silicon dioxide dielectric beam splitter and chromium/gold micro-mirrors. These optical components are deposited on 45° tilted surfaces to allow the horizontal/vertical separation of the incident beam in the final micro-integrated system. The fabrication process consists of 45° saw dicing of a glass substrate and the subsequent deposition of dielectric multilayers and metal layers. The ...

      Read Full Article
    9. High-resolution and nondestructive profile measurement by spectral-domain optical coherence tomography with a visible broadband light source for optical-device fabrication

      High-resolution and nondestructive profile measurement by spectral-domain optical coherence tomography with a visible broadband light source for optical-device fabrication

      We developed a spectral-domain optical coherence tomography (OCT) using a visible broadband light source (vis-OCT) for application to high-resolution and nondestructive profile measurement and imaging in semiconductor optical-device fabrication. By using visible broadband light centered at 625 nm and with spectral bandwidth of 260 nm, an axial resolution of 0.69 µm in air was obtained. This was effective for inspection of a transparent photoresist film with thickness of 1–2 µm coated on a semiconductor wafer; the interface between the photoresist film and its substrate and the interface between the photoresist and air were resolved, and the film thickness ...

      Read Full Article
    10. Optical module to extend any Fourier-domain optical coherence tomography system into a polarisation-sensitive system

      Optical module to extend any Fourier-domain optical coherence tomography system into a polarisation-sensitive system

      This article presents a theoretical study on an optical module (OM) that can be inserted between an object under investigation and a Fourier-domain optical coherence tomography system, transforming the latter into a polarisation-sensitive optical coherence tomography optical coherence tomography (OCT) system. The module consists of two electro-optic modulators, a Faraday rotator, a linear polariser and a quarter-wave plate. A detailed description on how the module can be used to extract both the net retardance and the fast axis orientation of a linear birefringent sample is presented. This is achieved by taking two sequential measurements for different values of retardance produced ...

      Read Full Article
    11. Microrheology of complex fluids

      Microrheology of complex fluids

      The field of microrheology is concerned with how materials store and dissipate mechanical energy as a function of length scale. Recent developments in the theory and instrumentation of the microrheology of complex fluids are reviewed. Equal emphasis is given to the physical phenomena probed, advances in instrumentation, and specific experimental systems in which this field has already had an impact. The inversion of the compliance data, measurement of sample heterogeneity, high frequency viscoelasticity, effects of shear flow, single molecule experiments, surface viscoelasticity and time evolution studies are considered. The techniques highlighted include particle tracking microrheology, diffusing wave spectroscopy, laser tracking ...

      Read Full Article
    12. The diagnosis of nasopharyngeal carcinoma by optical coherence tomography (OCT)

      The diagnosis of nasopharyngeal carcinoma by optical coherence tomography (OCT)

      We have attempted to explore the intrinsic differences in the optical properties of the nasopharyngeal carcinoma (NPC) and normal tissue by optical coherence tomography (OCT). OCT imaging of normal tissue provided three layers of epithelium, lamina propria, and the brighter interface of basement membrane; while carcinomas disrupted the layered construction embedded in signal-poor images. The morphologies were consistent with histological findings. Sensitivity and specificity were 90% and 100%, respectively. This pilot study demonstrates that NPC could be diagnosed by visualization, which implies that OCT might be potentially used to differentiate normal from NPC tissue in the early stage as an ...

      Read Full Article
    13. Optical coherence photoacoustic microscopy (OC-PAM) with an intensity-modulated continuous-wave broadband light source

      Optical coherence photoacoustic microscopy (OC-PAM) with an intensity-modulated continuous-wave broadband light source

      We developed an optical coherence photoacoustic microscopy system using an intensity-modulated continuous-wave superluminescent diode with a center wavelength of 840 nm. The system can accomplish optical coherence tomography (OCT) and photoacoustic microscopy (PAM) simultaneously. Compared to the system with a pulsed light source, this system is able to achieve OCT imaging with quality as high as conventional spectral-domain OCT. Since both of the OCT and PAM images are generated from the same group of photons, they are intrinsically registered in the lateral directions. The system was tested for multimodal imaging the vasculature of mouse ear in vivo by using gold ...

      Read Full Article
    14. Three-dimensional image reconstruction of macula from stratus optical coherence tomography (OCT) fordiagnosis of macular degeneration

      Three-dimensional image reconstruction of macula from stratus optical coherence tomography (OCT) fordiagnosis of macular degeneration

      Diagnosis of macular degeneration using a Stratus OCT with a fast macular thickness map (FMTM) method produced six B-scan images of macula from different angles. The images were converted into a retinal thickness chart to be evaluated by normal distribution percentile of data so that it can be classified as normal thickness of macula or as experiencing abnormality (e.g. thickening and thinning). Unfortunately, the diagnostic images only represent the retinal thickness in several areas of the macular region. Thus, this study is aims to obtain the entire retinal thickness in the macula area from Status OCT's output images ...

      Read Full Article
    15. Optical coherence tomography: an experimental validation for vascular imaging of saphenous vein bypass grafts

      Optical coherence tomography: an experimental validation for vascular imaging of saphenous vein bypass grafts

      Purpose. Optical coherence tomography (OCT) is a novel light-based intravascular imaging method with potential utility for quantifying vascular disease and the effect of therapy. OCT has been used to image vein grafts and neointima in clinical research studies but validity of OCT for vein graft imaging is limited by depth of field and tissue penetration. Experiments were carried out to validate the in-house developed new software (Medipass-iScan) and OCT vendor software comparing with a gold standard, photomicroscopy. Methods. Seven synthetic phantom tubes with varying inner diameters and eight saphenous veins were imaged with OCT. Imaging was performed five times on ...

      Read Full Article
    16. Correction of aberrations in digital holography using the phase gradient autofocus technique

      Correction of aberrations in digital holography using the phase gradient autofocus technique

      We propose a method for correcting aberrations in digital holography based on the principles of computational adaptive optics using the phase gradient autofocus technique that demands no reference measurements. The method requires a priori information on the relative positions of the elements of the optical setup. It is applicable for sufficiently smooth optical aberrations. This technique does not impose any restrictions on the magnitude of the scattered optical field phase distortions caused by the object structure. The efficacy of the proposed method is demonstrated through numerical simulation and experimental verification.

      Read Full Article
    17. Volumetric monitoring of aqueous two phase system droplets using time-lapse optical coherence tomography

      Volumetric monitoring of aqueous two phase system droplets using time-lapse optical coherence tomography

      We present a volumetric monitoring method to observe the morphological changes of aqueous two phase system (ATPS) droplets in a microfluidic system. Our method is based on time-lapse optical coherence tomography (OCT) which allows the study of the dynamics of ATPS droplets while visualizing their 3D structures and providing quantitative information on the droplets. In this study, we monitored the process of rehydration and deformation of an ATPS droplet in a microfluidic system and quantified the changes of its volume and velocity under both static and dynamic fluid conditions. Our results indicate that time-lapse OCT is a very promising tool ...

      Read Full Article
    18. Imaging colon cancer development in mice: IL-6 deficiency prevents adenoma in azoxymethane-treated Smad3 knockouts

      Imaging colon cancer development in mice: IL-6 deficiency prevents adenoma in azoxymethane-treated Smad3 knockouts

      The development of colorectal cancer in the azoxymethane-induced mouse model can be observed by using a miniaturized optical coherence tomography (OCT) imaging system. This system is uniquely capable of tracking disease development over time, allowing for the monitoring of morphological changes in the distal colon due to tumor development and the presence of lymphoid aggregates. By using genetically engineered mouse models deficient in Interleukin 6 (IL-6) and Smad family member 3 (Smad3), the role of inflammation on tumor development and the immune system can be elucidated. Smad3 knockout mice develop inflammatory response, wasting, and colitis associated cancer while deficiency of ...

      Read Full Article
    19. High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band

      High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band

      We describe the generation of a high-power, spectrally smooth supercontinuum (SC) in the 1600 nm spectral band for ultrahigh-resolution optical coherence tomography (UHR-OCT). A clean SC was achieved by using a highly nonlinear fiber with normal dispersion properties and a high-quality pedestal-free pulse obtained from a passively mode-locked erbium-doped fiber laser operating at 182 MHz. The center wavelength and spectral width were 1578 and 172 nm, respectively. The output power of the SC was 51 mW. Using the developed SC source, we demonstrated UHR-OCT imaging of biological samples with a sensitivity of 109 dB and an axial resolution of 4 ...

      Read Full Article
    20. Monte Carlo simulation of optical coherence tomography signal of the skin nevus

      Monte Carlo simulation of optical coherence tomography signal of the skin nevus

      Monte Carlo (MC) numerical simulation of light propagation in living tissue is widely used for characterization of optical coherence tomography (OCT) signals. Using MC simulation we obtained OCT images of skin with dysplastic nevus. Two various positions of skin nevus in depth were considered. Comparing these OCT simulation results with image of skin without nevus, we showed that OCT medical approach allows to detect dysplastic nevus at different stages of its life.

      Read Full Article
    21. Improved motion contrast and processing efficiency in OCT angiography using complex-correlation algorithm

      Improved motion contrast and processing efficiency in OCT angiography using complex-correlation algorithm

      The complex-based OCT angiography (Angio-OCT) offers high motion contrast by combining both the intensity and phase information. However, due to involuntary bulk tissue motions, complex-valued OCT raw data are processed sequentially with different algorithms for correcting bulk image shifts (BISs), compensating global phase fluctuations (GPFs) and extracting flow signals. Such a complicated procedure results in massive computational load. To mitigate such a problem, in this work, we present an inter-frame complex-correlation (CC) algorithm. The CC algorithm is suitable for parallel processing of both flow signal extraction and BIS correction, and it does not need GPF compensation. This method provides high ...

      Read Full Article
    22. Ultrahigh-resolution optical coherence tomography at 1.3 μm central wavelength by using a supercontinuum source pumped by noise-like pulses

      Ultrahigh-resolution optical coherence tomography at 1.3 μm central wavelength by using a supercontinuum source pumped by noise-like pulses

      We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power supercontinuum (SC) light source generated by noise-like pulses from an Yb-doped fiber laser. The SC spectrum is flat with a bandwidth of 420 nm centered around ~1.3 μ m. The light source is successfully employed in a time-domain OCT (TD-OCT), achieving an axial resolution of 2.3 μ m. High resolution fiber-based spectral-domain OCT (SD-OCT) imaging of bio-tissue was also demonstrated.

      Read Full Article
    23. One step geometrical calibration method for optical coherence tomography

      One step geometrical calibration method for optical coherence tomography

      We present a novel one-step calibration methodology for geometrical distortion correction for optical coherence tomography (OCT). A calibration standard especially designed for OCT is introduced, which consists of an array of inverse pyramidal structures. The use of multiple landmarks situated on four different height levels on the pyramids allow performing a 3D geometrical calibration. The calibration procedure itself is based on a parametric model of the OCT beam propagation. It is validated by experimental results and enables the reduction of systematic errors by more than one order of magnitude. In future, our results can improve OCT image reconstruction and interpretation ...

      Read Full Article
    24. Real Time Signal Processing and Data Handling with dedicated hardware in handheld OCT Device

      Real Time Signal Processing and Data Handling with dedicated hardware in handheld OCT Device

      The manuscript presents the topics on real time signal processing with dedicated hardware presented at the INFIERI Summer School 2014. The focus of this work is on real-time signal processing, filtering and massive parallel computing. In general, medical devices have stringed demands on energy consumption as well as on data processing and handling. In fact, the development of novel medical devices has led to significant advances in fields such as instrumentation, algorithm development and image processing. In this manuscript, two aspects of the design are brought into consideration: the transformation of a conventional signal processing algorithm into an equivalent version ...

      Read Full Article
    1-24 of 146 1 2 3 4 5 6 »
  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