1. 1-24 of 638 1 2 3 4 ... 25 26 27 »
    1. Contrast-enhanced optical coherence microangiography with acoustic-actuated microbubbles

      Contrast-enhanced optical coherence microangiography with acoustic-actuated microbubbles

      In this study, we propose to use gas-filled microbubbles (MBs) simultaneously actuated by the acoustic wave to enhance the imaging contrast of optical coherence tomography (OCT)-based angiography. In the phantom experiments, MBs can result in stronger backscattered intensity, enabling to enhance the contrast of OCT intensity image. Moreover, simultaneous application of low-intensity acoustic wave enables to temporally induce local vibration of particles and MBs in the vessels, resulting in time-variant OCT intensity which can be used for enhancing the contrast of OCT intensitybased angiography. Additionally, different acoustic modes and different acoustic powers to actuate MBs are performed and compared ...

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    2. Application of wearable optical coherence tomography (OCT) and Loop-mediated isothermal amplification (LAMP) techniques for In situ real-time field inspection of apple Marssonina blotch disease

      Application of wearable optical coherence tomography (OCT) and Loop-mediated isothermal amplification (LAMP) techniques for In situ real-time field inspection of apple Marssonina blotch disease

      Here we describe the possible application of optical coherence tomography (OCT) to inspect Marssonina coronaria infected apple blotch disease of in situ apple leaves. To fulfill the in situ field inspection requirement, we developed a compact wearable OCT system. For the confirmation of OCT results, simultaneous experiment was performed in realtime using loop-mediated isothermal amplification (LAMP), which is frequently used in agriculture. LAMP method was developed as an alternative approach for the inspection of disease. We performed field inspection for 30 consecutive days, and all the acquired results from both OCT and lamp were compared to confirm the correlation. A ...

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    3. A 3.4-mm beam diameter system for retinal imaging with OCT and adaptive optics

      A 3.4-mm beam diameter system for retinal imaging with OCT and adaptive optics

      We present an adaptive-optics optical coherence tomography (AO-OCT) system with 3.4-mm beam diameter. A deformable mirror is used for the correction of two radial Zernike orders (defocus, vertical and oblique astigmatism). The aberrations are corrected sequentially with a Shack-Hartmann wave-front sensor and the deformable mirror. This system fills a gap between a standard clinical 1.2-mm beam diameter OCT system and a 6-mm beam diameter AO-OCT system. We also present 8° by 8° en face OCT images from a patient with macular degeneration. This system has a 25 cm by 50 cm footprint, which makes it considerably smaller to ...

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      Mentions: Barry Cense
    4. Observation of elastic wave propagation near tissue surface using swept-source optical coherence tomography

      Observation of elastic wave propagation near tissue surface using swept-source optical coherence tomography

      Dynamic optical coherence elastography (OCE) is expected as new diagnostic technology of near tissue surface. However, few studies about shear wave propagation in inhomogeneous medium have been reported although human tissue is inhomogeneous medium. In this report, estimation of shear wave speeds and strain images of inhomogeneous medium were studied using swept-source optical coherence tomography (SS-OCT) system. Firstly, the shear wave speeds of four-layered chicken sample were measured. Secondly, OCT images of tissue mimicking phantoms, which included thread and aluminum wire were measured and strain distributions were calculated by PIV. Reflection and artifact of strain images were discussed.

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    5. Noninvasive imaging of oral mucosae with optical coherence tomography

      Noninvasive imaging of oral mucosae with optical coherence tomography

      In this study, a swept-source optical coherence tomography (OCT) system is developed for in vivo visualization of structural and vascular morphology oral mucosa. For simplification of optical probe fabrication, probe weight, and system setup, the body of the scanning probe is fabricated by a 3D printer to fix the optical components and the mechanical scanning device, and a partially reflective slide is attached at the output end of probe to achieve a common-path configuration. Aside from providing the ability of 3D structural imaging with the developed system, 3D vascular images of oral mucosa can be simultaneously obtained. Then, different locations ...

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    6. Dual illumination for cornea and retina imaging using spectral domain optical coherence tomography

      Dual illumination for cornea and retina imaging using spectral domain optical coherence tomography

      A dual illumination system is proposed for cornea and retina imaging using spectral domain optical coherence tomography (SD-OCT). The system is designed to acquire cornea and retina imaging with dual illumination with limited optics and using a single spectrometer. The beam propagation for cornea and retina imaging in dual illumination enables to acquire the images of different segments. This approach will reduce the imaging time for separate corneal and retinal imaging. The in vivo imaging of both the cornea and retina of a health volunteer shows the feasibility of the system for clinical applications.

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    7. Study on laser-assisted drug delivery with optical coherence tomography

      Study on laser-assisted drug delivery with optical coherence tomography

      The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. Nail plate divided into three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO 2 laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. Moreover, optical coherence tomography (OCT) is implemented for real-time monitoring of the laser–skin tissue interaction, sparing the patient from invasive surgical sampling procedure. Observations of drug diffusion through the induced ...

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    8. Multi-contrast imaging of human posterior eye by Jones matrix optical coherence tomography

      Multi-contrast imaging of human posterior eye by Jones matrix optical coherence tomography

      A multi-contrast imaging of pathologic posterior eyes is demonstrated by Jones matrix optical coherence tomography (Jones matrix OCT). The Jones matrix OCT provides five tomographies, which includes scattering, local attenuation, birefringence, polarization uniformity, and optical coherence angiography, by a single scan. The hardware configuration, algorithms of the Jones matrix OCT as well as its application to ophthalmology is discussed.

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    9. Ultra-high resolution polarization-sensitive optical coherence tomography for imaging of the retinal nerve fiber layer

      Ultra-high resolution polarization-sensitive optical coherence tomography for imaging of the retinal nerve fiber layer

      A spectrometer design with a multiple line line-scan camera and beam displacer is presented for ultra-high resolution optical coherence tomography measurements of the human retina at 840 nm. The beam displacer offsets the two orthogonal polarization states on the same line-scan camera, which reduces k-space mapping complexity, as data in both polarization channels can be mapped with the same procedure. Its coherence length is 2.8 μm in tissue (n = 1.38). Birefringence values of 1°/μm and higher were found in a circle with a radius of 2.5° eccentricity centered on the fovea, and in the raphe, pointing ...

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      Mentions: Barry Cense
    10. Ultra-deep imaging of optical coherence tomography in highly scattering media

      Ultra-deep imaging of optical coherence tomography in highly scattering media

      A time-domain optical coherence tomography system based on measuring the reflection matrix of back-scattered light is proposed for extended imaging depth into scattering media. A filtering operation is applied to the reflection matrix to preserve the back-scattered light with near-forward directions while discarding most of the multiple scattered light. A singular value decomposition is then carried out in the filtered matrix for principal component analysis, to remove the residual multi-scattered light. The results show the near-forward propagating single scattered light, which is mostly discarded in conventional OCT, can be separated computationally to increase the penetration depth of OCT.

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    11. External amplification of OCT swept-sources for challenging applications: from 10 mW to more than 120 mW

      External amplification of OCT swept-sources for challenging applications: from 10 mW to more than 120 mW

      For bioimaging applications, commercial swept-sources currently provide enough power (tens of milliwatts) insuring good imaging condition without damaging the tissues. For industrial applications, more power is needed since the amount of light collected can be very low due to challenging measurement conditions or due to poor sample reflectivity. To address this challenge, we explore three different setups to externally amplify the output of a commercial swept-source: a booster semiconductor optical amplifier (BOA), an erbium-doped fiber amplifier (EDFA) and a combination of both. These external amplification setups allow the exploration of emerging OCT applications without the need to develop new hardware.

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    12. Comparing an FFT filter for multiple reference optical coherence tomography (MR-OCT) with an Chebychev and an elliptic filter

      Comparing an FFT filter for multiple reference optical coherence tomography (MR-OCT) with an Chebychev and an elliptic filter

      Portable and low-cost optical coherence tomography (OCT) is increasingly used to improve the accuracy of point-of-care applications. The increasing research efforts to use photonics integrated circuits (PIC) is without doubts the future for highest packaging densities in miniature optical systems. MR-OCT is another technology that is using the advantages of well known CD/DVD-ROM technology to build miniaturized and low-cost OCT systems and may be more readily available before PICs reach their full potential. For MR-OCT it is essential to separate the the multiple signals originating from the multiple reflections of the partial mirror in the reference arm of Michelson ...

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    13. Noninvasive control of influence of polyethylene glycol on transport function of fluorescent colored liposomal nanoparticles

      Noninvasive control of influence of polyethylene glycol on transport function of fluorescent colored liposomal nanoparticles

      The studies were carried out on groups of clinically healthy mice line of outbred CD-1 stock. The model animals were divided into 2 groups and received experimental liposomal formulations. Using the method of fluorescence spectroscopy, we investigated the effectiveness of penetration into the circulatory system of fluorescently stained liposomes with polyethylene glycol (PEG) and without PEG when administered orally. Fluorescence channel with a fiber probe series of multifunctional laser non-invasive diagnostic system “LAKK-M” (SPE “LAZMA” Ltd, Russia) was used as the measuring equipment.

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    14. Monte-Carlo simulation of OCT structural images of human skin using experimental B-scans and voxel based approach to optical properties distribution

      Monte-Carlo simulation of OCT structural images of human skin using experimental B-scans and voxel based approach to optical properties distribution

      A method of optical coherence tomography (OCT) structural images reconstruction using Monte Carlo simulations is described. Biological object is considered as a set of 3D elements that allow simulation of media, structure of which cannot be described analytically. Each voxel is characterized by its refractive index and anisotropy parameter, scattering and absorption coefficients. B-scans of the inner structure are used to reconstruct a simulated image instead of analytical representation of the boundary geometry. Henye-Greenstein scattering function, Beer-Lambert-Bouguer law and Fresnel equations are used for photon transport description. Efficiency of the described technique is checked by the comparison of the simulated ...

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    15. Improving graph-based OCT segmentation for severe pathology in retinitis pigmentosa patients

      Improving graph-based OCT segmentation for severe pathology in retinitis pigmentosa patients

      Three dimensional segmentation of macular optical coherence tomography (OCT) data of subjects with retinitis pigmentosa (RP) is a challenging problem due to the disappearance of the photoreceptor layers, which causes algorithms developed for segmentation of healthy data to perform poorly on RP patients. In this work, we present enhancements to a previously developed graph-based OCT segmentation pipeline to enable processing of RP data. The algorithm segments eight retinal layers in RP data by relaxing constraints on the thickness and smoothness of each layer learned from healthy data. Following from prior work, a random forest classifier is first trained on the ...

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    16. An automated image processing method for classification of diabetic retinopathy stages from conjunctival microvasculature images

      An automated image processing method for classification of diabetic retinopathy stages from conjunctival microvasculature images

      The conjunctiva is a densely vascularized tissue of the eye that provides an opportunity for imaging of human microcirculation. In the current study, automated fine structure analysis of conjunctival microvasculature images was performed to discriminate stages of diabetic retinopathy (DR). The study population consisted of one group of nondiabetic control subjects (NC) and 3 groups of diabetic subjects, with no clinical DR (NDR), non-proliferative DR (NPDR), or proliferative DR (PDR). Ordinary least square regression and Fisher linear discriminant analyses were performed to automatically discriminate images between group pairs of subjects. Human observers who were masked to the grouping of subjects ...

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      Mentions: Mahnaz Shahidi
    17. Analysis of polygonal scanning heads: from industrial to high-end applications in swept sources for OCT

      Analysis of polygonal scanning heads: from industrial to high-end applications in swept sources for OCT

      An analysis of polygonal mirror (PM) scanning heads has been performed, in order to provide a tool for their optimal design. The theory developed brings under the same umbrella applications that range from industrial dimensional measurements to high-end biomedical imaging, for example for broadband laser sources swept in frequency for Swept Source Optical Coherence Tomography (SS-OCT). The different characteristic parameters of the PM scanning heads were considered in order to achieve a rigorous analysis: number of PM facets, inner radius of the PM, eccentricity of the PM pivot with regard to the incident fixed laser beam, distance from this beam ...

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    18. Collaborative SDOCT segmentation and analysis software

      Collaborative SDOCT segmentation and analysis software

      Spectral domain optical coherence tomography (SDOCT) is routinely used in the management and diagnosis of a variety of ocular diseases. This imaging modality also finds widespread use in research, where quantitative measurements obtained from the images are used to track disease progression. In recent years, the number of available scanners and imaging protocols grown and there is a distinct absence of a unified tool that is capable of visualizing, segmenting, and analyzing the data. This is especially noteworthy in longitudinal studies, where data from older scanners and/or protocols may need to be analyzed. Here, we present a graphical user ...

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    19. Longitudinal analysis of mouse SDOCT volumes

      Longitudinal analysis of mouse SDOCT volumes

      Spectral-domain optical coherence tomography (SDOCT), in addition to its routine clinical use in the diagnosis of ocular diseases, has begun to fund increasing use in animal studies. Animal models are frequently used to study disease mechanisms as well as to test drug efficacy. In particular, SDOCT provides the ability to study animals longitudinally and non-invasively over long periods of time. However, the lack of anatomical landmarks makes the longitudinal scan acquisition prone to inconsistencies in orientation. Here, we propose a method for the automated registration of mouse SDOCT volumes. The method begins by accurately segmenting the blood vessels and the ...

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    20. Extraction of membrane structure in eyeball from MR volumes

      Extraction of membrane structure in eyeball from MR volumes

      This paper presents an accurate extraction method of spherical shaped membrane structures in the eyeball from MR volumes. In ophthalmic surgery, operation field is limited to a small region. Patient specific surgical simulation is useful to reduce complications. Understanding of tissue structure in the eyeball of a patient is required to achieve patient specific surgical simulations. Previous extraction methods of tissue structure in the eyeball use optical coherence tomography (OCT) images. Although OCT images have high resolution, imaging regions are limited to very small. Global structure extraction of the eyeball is difficult from OCT images. We propose an extraction method ...

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    21. A spatially variant deconvolution method based on total variation for optical coherence tomography images

      A spatially variant deconvolution method based on total variation for optical coherence tomography images

      Optical Coherence Tomography (OCT) has a great potential to elicit clinically useful information from tissues due to its high axial and transversal resolution. In practice, an OCT setup cannot reach to its theoretical resolution due to imperfections of its components, which make its images blurry. The blurriness is different alongside regions of image; thus, they cannot be modeled by a unique point spread function (PSF). In this paper, we investigate the use of solid phantoms to estimate the PSF of each sub-region of imaging system. We then utilize Lucy-Richardson, Hybr and total variation (TV) based iterative deconvolution methods for mitigating ...

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    22. An intelligent despeckling method for swept source optical coherence tomography images of skin

      An intelligent despeckling method for swept source optical coherence tomography images of skin

      Optical Coherence Optical coherence tomography is a powerful high-resolution imaging method with a broad biomedical application. Nonetheless, OCT images suffer from a multiplicative artefacts so-called speckle, a result of coherent imaging of system. Digital filters become ubiquitous means for speckle reduction. Addressing the fact that there still a room for despeckling in OCT, we proposed an intelligent speckle reduction framework based on OCT tissue morphological, textural and optical features that through a trained network selects the winner filter in which adaptively suppress the speckle noise while preserve structural information of OCT signal. These parameters are calculated for different steps of ...

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    23. Inter-session repeatability of retinal layer thickness in optical coherence tomography

      Inter-session repeatability of retinal layer thickness in optical coherence tomography

      Reliable retinal layer thickness measurements using optical coherence tomography (OCT) are important to track the subtle retinal changes in longitudinal studies. A total of 10 eyes (5 healthy subjects, 40±13 years old) were enrolled to study the inter-session repeatability and identify the pitfalls affecting the reliabilities. Each eye was scanned using spectral domain OCT (Spectralis SDOCT, Heidelberg Engineering) for 3 sessions with 30 seconds rest in between. The first and second sessions were scanned independently and the third one was scanned with the first one as the baseline visit. Each session consisted of a confocal scanning laser ophthalmoscopy (cSLO ...

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    24. A comparative study of noise in supercontinuum light sources for ultra-high resolution optical coherence tomography at 1300 nm

      A comparative study of noise in supercontinuum light sources for ultra-high resolution optical coherence tomography at 1300 nm

      Supercontinuum (SC) light is a well-established technology, which finds applications in several domains ranging from chemistry to material science and imaging systems [1-2]. More specifically, its ultra-wide optical bandwidth and high average power make it an ideal tool for Optical Coherence Tomography (OCT). Over the last 5 years, numerous examples have demonstrated its high potential [3-4] in this context. However, SC light sources present pulse-to-pulse intensity variation that can limit the performance of any OCT system [5] by degrading their signal to noise ratio (SNR). To this goal, we have studied and compared the noise of several SC light sources ...

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    1-24 of 638 1 2 3 4 ... 25 26 27 »
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