1. Articles from opticsinfobase.org

  2. 1-24 of 1198 1 2 3 4 ... 48 49 50 »
    1. Measuring the optical characteristics of medulloblastoma with optical coherence tomography

      Measuring the optical characteristics of medulloblastoma with optical coherence tomography

      Medulloblastoma is the most common malignant pediatric brain tumor. Standard treatment consists of surgical resection, followed by radiation and high-dose chemotherapy. Despite these efforts, recurrence is common, leading to reduced patient survival. Even with successful treatment, there are often severe long-term neurologic impacts on the developing nervous system. We present two quantitative techniques that use a high-resolution optical imaging modality: optical coherence tomography (OCT) to measure refractive index, and the optical attenuation coefficient. To the best of our knowledge, this study is the first to demonstrate OCT analysis of medulloblastoma. Refractive index and optical attenuation coefficient were able to differentiate ...

      Read Full Article
    2. Quantitative microvascular hemoglobin mapping using visible light spectroscopic Optical Coherence Tomography

      Quantitative microvascular hemoglobin mapping using visible light spectroscopic Optical Coherence Tomography

      Quantification of chromophore concentrations in reflectance mode remains a major challenge for biomedical optics. Spectroscopic Optical Coherence Tomography (SOCT) provides depth-resolved spectroscopic information necessary for quantitative analysis of chromophores, like hemoglobin, but conventional SOCT analysis methods are applicable only to well-defined specular reflections, which may be absent in highly scattering biological tissue. Here, by fitting of the dynamic scattering signal spectrum in the OCT angiogram using a forward model of light propagation, we quantitatively determine hemoglobin concentrations directly. Importantly, this methodology enables mapping of both oxygen saturation and total hemoglobin concentration, or alternatively, oxyhemoglobin and deoxyhemoglobin concentration, simultaneously. Quantification was ...

      Read Full Article
    3. Differential diagnosis of human bladder mucosa pathologies in vivo with cross-polarization optical coherence tomography

      Differential diagnosis of human bladder mucosa pathologies in vivo with cross-polarization optical coherence tomography

      Quantitative image analysis and parameter extraction using a specific implementation of polarization-sensitive optical coherence tomography (OCT) provides differential diagnosis of mucosal pathologies in in-vivo human bladders. We introduce a cross-polarization (CP) OCT image metric called Integral Depolarization Factor (IDF) to enable automatic diagnosis of bladder conditions (assessment the functional state of collagen fibers). IDF-based diagnostic accuracy of identification of the severe fibrosis of normal bladder mucosa is 79%; recurrence of carcinoma on the post-operative scar is 97%; and differentiation between neoplasia and acute inflammation is 75%. The promising potential of CP OCT combined with image analysis in human urology is ...

      Read Full Article
    4. In vivo molecular contrast OCT imaging of methylene blue

      In vivo molecular contrast OCT imaging of methylene blue

      An 830-nm spectral-domain optical coherence tomography (OCT) system with an integrated 663-nm diode pump laser has been developed to enable molecular contrast OCT imaging of methylene blue (MB), a common vital dye used clinically. The introduction of the 663-nm diode laser, which acts as the pump in this implementation of pump-probe OCT (PPOCT), represents a minor modification to an otherwise typical OCT system. A newly developed background subtraction technique completely removes all background from intensity noise at the pump modulation frequency, simplifying the interpretation of PPOCT images. These developments have enabled the first in vivo imaging of MB with PPOCT ...

      Read Full Article
    5. Imaging of retinal vasculature using adaptive optics SLO/OCT

      Imaging of retinal vasculature using adaptive optics SLO/OCT

      We use our previously developed adaptive optics (AO) scanning laser ophthalmoscope (SLO)/ optical coherence tomography (OCT) instrument to investigate its capability for imaging retinal vasculature. The system records SLO and OCT images simultaneously with a pixel to pixel correspondence which allows a direct comparison between those imaging modalities. Different field of views ranging from 0.8°x0.8° up to 4°x4° are supported by the instrument. In addition a dynamic focus scheme was developed for the AO-SLO/OCT system in order to maintain the high transverse resolution throughout imaging depth. The active axial eye tracking that is implemented in ...

      Read Full Article
    6. Optical coherence photoacoustic microscopy for in vivo multimodal retinal imaging

      Optical coherence photoacoustic microscopy for in vivo multimodal retinal imaging

      We developed an optical coherence photoacoustic microscopy (OC-PAM) system, which can accomplish optical coherence tomography (OCT) and photoacoustic microscopy (PAM) simultaneously by using a single pulsed broadband light source. With a center wavelength of 800 nm and a bandwidth of 30 nm, the system is suitable for imaging the retina. Generated from the same group of photons, the OCT and PAM images are intrinsically registered in the lateral directions. To test the capabilities of the system on multimodal ophthalmic imaging, we imaged the retina of pigmented rats. The OCT images showed the retinal structures with quality similar to conventional OCT ...

      Read Full Article
    7. Ex vivo catheter-based imaging of coronary atherosclerosis using multimodality OCT and NIRAF excited at 633 nm

      Ex vivo catheter-based imaging of coronary atherosclerosis using multimodality OCT and NIRAF excited at 633 nm

      While optical coherence tomography (OCT) has been shown to be capable of imaging coronary plaque microstructure, additional chemical/molecular information may be needed in order to determine which lesions are at risk of causing an acute coronary event. In this study, we used a recently developed imaging system and double-clad fiber (DCF) catheter capable of simultaneously acquiring both OCT and red excited near-infrared autofluorescence (NIRAF) images (excitation: 633 nm, emission: 680nm to 900nm). We found that NIRAF is elevated in lesions that contain necrotic core – a feature that is critical for vulnerable plaque diagnosis and that is not readily discriminated ...

      Read Full Article
    8. High-performance multi-megahertz optical coherence tomography based on amplified optical time-stretch

      High-performance multi-megahertz optical coherence tomography based on amplified optical time-stretch

      As the key prerequisite of high-speed volumetric structural and functional tissue imaging in real-time, scaling the A-scan rate beyond MHz has been one of the major pursuits in the development of optical coherence tomography (OCT). Along with a handful of techniques enabling multi-MHz, amplified optical time-stretch OCT (AOT-OCT) has recently been demonstrated as a viable alternative for ultrafast swept-source OCT well above MHz without the need for the mechanical wavelength-tuning mechanism. In this paper, we report a new generation of AOT-OCT demonstrating superior performance to its older generation and all other time-stretch-based OCT modalities in terms of shot-to-shot stability, sensitivity ...

      Read Full Article
    9. Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler

      Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler

      Double-clad fiber (DCF) is herein used in conjunction with a double-clad fiber coupler (DCFC) to enable simultaneous and co-registered optical coherence tomography (OCT) and laser tissue coagulation. The DCF allows a single channel fiber-optic probe to be shared: i.e. the core propagating the OCT signal while the inner cladding delivers the coagulation laser light. We herein present a novel DCFC designed and built to combine both signals within a DCF (>90% of single-mode transmission; >65% multimode coupling). Potential OCT imaging degradation mechanisms are also investigated and solutions to mitigate them are presented. The combined DCFC-based system was used to ...

      Read Full Article
    10. Kernel regression based segmentation of optical coherence tomography images with diabetic macular edema

      Kernel regression based segmentation of optical coherence tomography images with diabetic macular edema

      We present a fully automatic algorithm to identify fluid-filled regions and seven retinal layers on spectral domain optical coherence tomography images of eyes with diabetic macular edema (DME). To achieve this, we developed a kernel regression (KR)-based classification method to estimate fluid and retinal layer positions. We then used these classification estimates as a guide to more accurately segment the retinal layer boundaries using our previously described graph theory and dynamic programming (GTDP) framework. We validated our algorithm on 110 Bscans from ten patients with severe DME pathology, showing an overall mean Dice coefficient of 0.78 when comparing ...

      Read Full Article
    11. 1.7 μm spectroscopic spectral-domain optical coherence tomography for imaging lipid distribution within blood vessel

      1.7 μm spectroscopic spectral-domain optical coherence tomography for imaging lipid distribution within blood vessel

      We have developed a spectroscopic optical coherence tomography (OCT) for imaging lipid distribution within blood vessel in order to detect coronary artery plaque. A 1.7-μm spectral-domain OCT with A-scan rate of 47 kHz is fabricated using a broadband light source based on super-luminescent diodes and spectrometers based on extended InGaAs line sensors. We demonstrate imaging of lipid distribution in an in vitro artery model with lipid. The sensitivity and specificity in the differentiation between artery and lipid are 87% and 90% in the training, respectively. The validation test also shows detection of lipid with an accuracy over 90%.

      Read Full Article
    12. Efficient method to suppress artifacts caused by tissue hyper-reflections in optical microangiography of retina in vivo

      Efficient method to suppress artifacts caused by tissue hyper-reflections in optical microangiography of retina in vivo

      Optical microangiography (OMAG) is an optical coherence tomography (OCT)-based imaging technique that is capable of achieving the angiographic imaging of biological tissues in vivo with a high imaging resolution and no need for dye injection. OMAG has a potential to become a clinical tool for the diagnosis and treatment monitoring of various retinopathies. In principle, OMAG extracts blood flow information based on a direct differentiation of complex or intensity OCT signals between repeated B-scans acquired at the same cross section, which is sensitive to blood cell movement. In practice, this method is prone to artifacts due to tissue hyper-reflection ...

      Read Full Article
    13. Anisotropic aberration correction using region of interest based digital adaptive optics in Fourier domain OCT

      Anisotropic aberration correction using region of interest based digital adaptive optics in Fourier domain OCT

      In this paper a numerical technique is presented to compensate for anisotropic optical aberrations, which are usually present across the lateral field of view in the out of focus regions, in high resolution optical coherence tomography and microscopy (OCT/OCM) setups. The recorded enface image field at different depths in the tomogram is digitally divided into smaller sub-regions or the regions of interest (ROIs), processed individually using subaperture based digital adaptive optics (DAO), and finally stitched together to yield a final image with a uniform diffraction limited resolution across the entire field of view (FOV). Using this method, a sub-micron ...

      Read Full Article
    14. Analyzing three-dimensional ultrastructure of human cervical tissue using optical coherence tomography

      Analyzing three-dimensional ultrastructure of human cervical tissue using optical coherence tomography

      During pregnancy, the uterine cervix is the mechanical barrier that prevents delivery of a fetus. The underlying cervical collagen ultrastructure, which influences the overall mechanical properties of the cervix, plays a role in maintaining a successful pregnancy until term. Yet, not much is known about this collagen ultrastructure in pregnant and nonpregnant human tissue. We used optical coherence tomography to investigate the directionality and dispersion of collagen fiber bundles in the human cervix. An image analysis tool has been developed, combining a stitching method with a fiber orientation measurement, to study axially sliced cervix samples. This tool was used to ...

      Read Full Article
    15. Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms

      Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms

      The fabrication of high-performance spherical gradient refractive index (S-GRIN) optics requires nondestructive metrology techniques to inspect the samples. We have developed an angular-scan, swept-source-based, Fourier-domain optical coherence tomography system centered at 1318 nm with 5 mm imaging depth capable of 180̊ polar scan and 360̊ azimuthal scan to investigate polymeric S-GRIN preforms. We demonstrate a method that enables simultaneous mapping of the group optical thickness, physical thickness, the radially-averaged group refractive index, and the transmitted wavefront of the S-GRIN preforms. The angular scan OCT imaging and metrology enables direct visualization, molding uniformity characterization, and optical property evaluations of the preforms ...

      Read Full Article
    16. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

      Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

      We provide a framework for compensating errors within passive optical quadrature demodulation circuits used in swept-source optical coherence tomography (OCT). Quadrature demodulation allows for detection of both the real and imaginary components of an interference fringe, and this information separates signals from positive and negative depth spaces. To achieve a high extinction (∼60 dB) between these positive and negative signals, the demodulation error must be less than 0.1% in amplitude and phase. It is difficult to construct a system that achieves this low error across the wide spectral and RF bandwidths of high-speed swept-source systems. In a prior work ...

      Read Full Article
    17. Line-field parallel swept source MHz OCT for structural and functional retinal imaging

      Line-field parallel swept source MHz OCT for structural and functional retinal imaging

      We demonstrate three-dimensional structural and functional retinal imaging with line-field parallel swept source imaging (LPSI) at acquisition speeds of up to 1 MHz equivalent A-scan rate with sensitivity better than 93.5 dB at a central wavelength of 840 nm. The results demonstrate competitive sensitivity, speed, image contrast and penetration depth when compared to conventional point scanning OCT. LPSI allows high-speed retinal imaging of function and morphology with commercially available components. We further demonstrate a method that mitigates the effect of the lateral Gaussian intensity distribution across the line focus and demonstrate and discuss the feasibility of high-speed optical angiography ...

      Read Full Article
    18. Depth-encoded synthetic aperture optical coherence tomography of biological tissues with extended focal depth

      Depth-encoded synthetic aperture optical coherence tomography of biological tissues with extended focal depth

      Optical coherence tomography (OCT) has proven to be able to provide three-dimensional (3D) volumetric images of scattering biological tissues for in vivo medical diagnostics. Unlike conventional optical microscopy, its depth-resolving ability (axial resolution) is exclusively determined by the laser source and therefore invariant over the full imaging depth. In contrast, its transverse resolution is determined by the objective’s numerical aperture and the wavelength which is only approximately maintained over twice the Rayleigh range. However, the prevailing laser sources for OCT allow image depths of more than 5 mm which is considerably longer than the Rayleigh range. This limits high ...

      Read Full Article
    19. Polarization sensitive optical frequency domain imaging system for endobronchial imaging

      Polarization sensitive optical frequency domain imaging system for endobronchial imaging

      A polarization sensitive endoscopic optical frequency domain imaging (PS-OFDI) system with a motorized distal scanning catheter is demonstrated. It employs a passive polarization delay unit to multiplex two orthogonal probing polarization states in depth, and a polarization diverse detection unit to detect interference signal in two orthogonal polarization channels. Per depth location four electro-magnetic field components are measured that can be represented in a complex 2x2 field matrix. A Jones matrix of the sample is derived and the sample birefringence is extracted by eigenvalue decomposition. The condition of balanced detection and the polarization mode dispersion are quantified. A complex field ...

      Read Full Article
    20. Spectral fractionation detection of gold nanorod contrast agents using optical coherence tomography

      Spectral fractionation detection of gold nanorod contrast agents using optical coherence tomography

      We demonstrate the proof of concept of a novel Fourier-domain optical coherence tomography contrast mechanism using gold nanorod contrast agents and a spectral fractionation processing technique. The methodology detects the spectral shift of the backscattered light from the nanorods by comparing the ratio between the short and long wavelength halves of the optical coherence tomography signal intensity. Spectral fractionation further divides the halves into sub-bands to improve spectral contrast and suppress speckle noise. Herein, we show that this technique can detect gold nanorods in intralipid tissue phantoms. Furthermore, cellular labeling by gold nanorods was demonstrated using retinal pigment epithelial cells ...

      Read Full Article
    21. Developing cross-correlation as a method for microvessel imaging using clinical intravascular optical coherence tomography systems

      Developing cross-correlation as a method for microvessel imaging using clinical intravascular optical coherence tomography systems

      Current clinical intravascular optical coherence tomography (IV-OCT) imaging systems have limited in-vivo flow imaging capability because of non-uniform catheter rotation and inadequate A-line scan density. Thus any flow-localisation method that seeks to identify sites of variation within the OCT image data-sets, whether that is in amplitude or phase, produces non-representative correlation (or variance) maps. In this study, both mean and the variation within a set of cross-correlation maps, for static OCT imaging was used to differentiate flow from nonflow regions. Variation was quantified by use of standard deviation. The advantage of this approach is its ability to image flow, even ...

      Read Full Article
    22. Simultaneous and localized measurement of diffusion and flow using optical coherence tomography

      Simultaneous and localized measurement of diffusion and flow using optical coherence tomography

      We report on the simultaneous and localized measurement of the diffusion coefficient and flow velocity based on the normalized autocorrelation function using optical coherence tomography (OCT). Our results on a flowing suspension of polystyrene spheres show that the flow velocity and the diffusion coefficient can be reliably estimated in a regime determined by the sample diffusivity, the local flow velocity, and the Gaussian beam waist. We experimentally demonstrate that a smaller beam waist results in an improvement of the velocity sensitivity at the expense of the precision and accuracy of the estimation of the diffusion coefficient. Further, we show that ...

      Read Full Article
    23. High resolution Fourier domain optical coherence tomography in the 2 μm wavelength range using a broadband supercontinuum source

      High resolution Fourier domain optical coherence tomography in the 2 μm wavelength range using a broadband supercontinuum source

      A 220 nm bandwidth supercontinuum source in the two-micron wavelength range has been developed for use in a Fourier domain optical coherence tomography (FDOCT) system. This long wavelength source serves to enhance probing depth in highly scattering material with low water content. We present results confirming improved penetration depth in high opacity paint samples while achieving the high axial resolution needed to resolve individual paint layers. This is the first FDOCT developed in the 2 μm wavelength regime that allows fast, efficient capturing of 3D image cubes at a high axial resolution of 13 μm in air (or 9 μm ...

      Read Full Article
    24. Full wave model of image formation in optical coherence tomography applicable to general samples

      Full wave model of image formation in optical coherence tomography applicable to general samples

      We demonstrate a highly realistic model of optical coherence tomography, based on an existing model of coherent optical microscopes, which employs a full wave description of light. A defining feature of the model is the decoupling of the key functions of an optical coherence tomography system: sample illumination, light-sample interaction and the collection of light scattered by the sample. We show how such a model can be implemented using the finite-difference time-domain method to model light propagation in general samples. The model employs vectorial focussing theory to represent the optical system and, thus, incorporates general illumination beam types and detection ...

      Read Full Article
    1-24 of 1198 1 2 3 4 ... 48 49 50 »
  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