1. Articles from opticsinfobase.org

  2. 1-24 of 1114 1 2 3 4 ... 45 46 47 »
    1. Detection of plasmonic nanoparticles with full field-OCT: optical and photothermal detection

      Detection of plasmonic nanoparticles with full field-OCT: optical and photothermal detection

      Detecting the signal backscattered by nanoparticles immersed in highly scattering media such as biological tissue remains a challenge. In this article we report on the use of Full Field OCT (FF-OCT) to slice in depth in phantoms and in tissues in order a) to selectively observe the particles through the backscattered light at suitable wavelengths, and b) to detect the effects of the time-dependent response to full field optical heating through the strong absorption cross-section of these plasmonic nanoparticles. The analysis of the thermal wave behavior leads to the localization of the heat sources even when FF-OCT signals cannot reach ...

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    2. Quantitative measurements of strain and birefringence with common-path polarization-sensitive optical coherence tomography

      Quantitative measurements of strain and birefringence with common-path polarization-sensitive optical coherence tomography

      We demonstrate the first system for optical coherence tomography (OCT) that enables simultaneous measurement of quantitative birefringence and strain in biological samples using a common-path configuration. Owing to its superior phase stability, common-path polarization sensitive optical coherence tomography (CoPPSe-OCT) achieves a sub-nanometer displacement sensitivity of 0.52 nm at an SNR of 48 dB. We utilize CoPPSe-OCT to measure reflectance, birefringence, and strain for distinguishing burnt regions in a birefringent biological sample (chicken breast muscle).

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    3. Optical microcavity scanning 3D tomography

      Optical microcavity scanning 3D tomography

      A scanning optical microcavity is exploited to achieve lens-free 3D tomography of microfluidic channels. The microcavity, powered by a low-coherence source, is realized by approaching a cleaved fiber to few tens of micrometers over the sample. The interference of scattered waves inside the cavity shapes the transverse field distribution by focusing the beam and overcoming the diffraction limit due to the optical-fiber numerical aperture. The focusing effect is also preserved in the inner layers of the sample, allowing optical 3D tomography. Analysis of microfluidic channels was demonstrated through this noninvasive technique. Although the experimental setup recalls the well-known fiber-optic Fourier-domain ...

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    4. In vivo functional microangiography by visible-light optical coherence tomography

      In vivo functional microangiography by visible-light optical coherence tomography

      Although hemoglobin oxygen saturation (sO 2 ) in the microvasculature is an essential physiological parameter of local tissue functions, non-invasive measurement of microvascular sO 2 is still challenging. Here, we demonstrated that visible-light optical coherence tomography (vis-OCT) can simultaneously provide three-dimensional anatomical tissue morphology, visualize microvasculature at the capillary level, and measure sO 2 from the microvasculature in vivo . We utilized speckle contrast caused by the moving blood cells to enhance microvascular imaging. We applied a series of short-time inverse Fourier transforms to obtain the spectroscopic profile of blood optical attenuation, from which we quantified sO 2 . We validated the sO ...

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    5. Fully automated detection of diabetic macular edema and dry age-related macular degeneration from optical coherence tomography images

      Fully automated detection of diabetic macular edema and dry age-related macular degeneration from optical coherence tomography images

      We present a novel fully automated algorithm for the detection of retinal diseases via optical coherence tomography (OCT) imaging. Our algorithm utilizes multiscale histograms of oriented gradient descriptors as feature vectors of a support vector machine based classifier. The spectral domain OCT data sets used for cross-validation consisted of volumetric scans acquired from 45 subjects: 15 normal subjects, 15 patients with dry age-related macular degeneration (AMD), and 15 patients with diabetic macular edema (DME). Our classifier correctly identified 100% of cases with AMD, 100% cases with DME, and 86.67% cases of normal subjects. This algorithm is a potentially impactful ...

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    6. Automatic detection of bioresorbable vascular scaffold struts in intravascular optical coherence tomography pullback runs

      Automatic detection of bioresorbable vascular scaffold struts in intravascular optical coherence tomography pullback runs

      Bioresorbable vascular scaffolds (BVS) have gained significant interest in both the technical and clinical communities as a possible alternative to metallic stents. For accurate BVS analysis, intravascular optical coherence tomography (IVOCT) is currently the most suitable imaging technique due to its high resolution and the translucency of polymeric BVS struts for near infrared light. However, given the large number of struts in an IVOCT pullback run, quantitative analysis is only feasible when struts are detected automatically. In this paper, we present an automated method to detect and measure BVS struts based on their black cores in IVOCT images. Validated using ...

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    7. OCT 3-D surface topography of isolated human crystalline lenses

      OCT 3-D surface topography of isolated human crystalline lenses

      Quantitative 3-D Optical Coherence Tomography was used to measure surface topography of 36 isolated human lenses, and to evaluate the relationship between anterior and posterior lens surface shape and their changes with age. All lens surfaces were fitted to 6th order Zernike polynomials. Astigmatism was the predominant surface aberration in anterior and posterior lens surfaces (accounting for ~55% and ~63% of the variance respectively), followed by spherical terms, coma, trefoil and tetrafoil. The amount of anterior and posterior surface astigmatism did not vary significantly with age. The relative angle between anterior and posterior surface astigmatism axes was on average 36 ...

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    8. Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT)

      Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT)

      Enabled by the ultrahigh-speed all-optical wavelength-swept mechanism and broadband optical amplification, amplified optical time-stretch optical coherence tomography (AOT-OCT) has recently been demonstrated as a practical alternative to achieve ultrafast A-scan rate of multi-MHz in OCT. With the aim of identifying the optimal scenarios for MHz operation in AOT-OCT, we here present a theoretical framework to evaluate its performance metric. In particular, the analysis discusses the unique features of AOT-OCT, such as its superior coherence length, and the relationship between the optical gain and the A-scan rate. More importantly, we evaluate the sensitivity of AOT-OCT in the MHz regime under the ...

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    9. Visible light optical coherence correlation spectroscopy

      Visible light optical coherence correlation spectroscopy

      Optical coherence correlation spectroscopy (OCCS) allows studying kinetic processes at the single particle level using the backscattered light of nanoparticles. We extend the possibilities of this technique by increasing its signal-to-noise ratio by a factor of more than 25 and by generalizing the method to solutions containing multiple nanoparticle species. We applied these improvements by measuring protein adsorption and formation of a protein monolayer on superparamagnetic iron oxide nanoparticles under physiological conditions.

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    10. Axicon on a gradient index lens (AXIGRIN): integrated optical bench for Bessel beam generation from a point-like source

      Axicon on a gradient index lens (AXIGRIN): integrated optical bench for Bessel beam generation from a point-like source

      We propose and demonstrate a novel concept of a compact optical component aimed at transforming a point-like source into a Bessel beam. This component, called AXIGRIN, consists of an axicon fabricated at the end facet of a gradient index lens. It can be directly coupled to an optical fiber, a microscope objective, or vertical-external-cavity surface-emitting-laser to be used without preliminary adjustments, which is of practical interest for end users. This opens new avenues in domains, such as imaging, particle acceleration and manipulation, optical coherence tomography, data storage, laser cutting, etc. AXIGRIN also opens the perspective of using Bessel beams for ...

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    11. Line-field parallel swept source interferometric imaging at up to 1MHz

      Line-field parallel swept source interferometric imaging at up to 1MHz

      We present a novel medical imaging modality based on optical coherence tomography (OCT) that enables in vivo 3D tomography at acquisition rates up to 1 MHz. Line field parallel swept source interferometric imaging (LPSI) combines line-field swept source OCT with modulation of the interferometric signal in spatial direction for full range imaging. This method enables high speed imaging with cost-effective and commercially available technology. We explain the realization of the LPSI setup, acquisition, and postprocessing and finally demonstrate 3D in vivo imaging of human nail fold. To the best of our knowledge, sensitivity and depth penetration are competitive with respective ...

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    12. Differentiation of ex vivo human breast tissue using polarization-sensitive optical coherence tomography

      Differentiation of ex vivo human breast tissue using polarization-sensitive optical coherence tomography

      Successful treatment of breast cancer typically requires surgical removal of the tumor. Optical coherence tomography (OCT) has been previously developed for real-time imaging of the surgical margin. However, it can be difficult to distinguish between normal stromal tissue and cancer tissue based on scattering intensity and structure alone. Polarization-sensitive optical coherence tomography (PS-OCT) is sensitive to form birefringence of biological tissue. We report on the development of a high-speed PS-OCT system and imaging of ex vivo human breast tissue, showing enhanced contrast between healthy and cancerous tissues based upon collagen content confirmed with corresponding histology. These results demonstrate the feasibility ...

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    13. Interference enhancement in spectral domain interferometric measurements on transparent plate

      Interference enhancement in spectral domain interferometric measurements on transparent plate

      In spectral domain interferometry, the interference signal generated by directly reflected waves from the two surfaces of a sample plate under test is greatly enhanced by the blockage of those light waves reflected by the two arm mirrors in the Michelson interferometer. This sample surface-reflected interference signal, being the optical path length of the plate, is therefore identifiable directly from the Fourier-transformed interference spectrum. Consequently, the group refractive index and physical thickness of the plate can be obtained simultaneously without any prior information of them. Moreover, subsequent in situ angular scanning on the interference spectra helps to retrieve the wavelength-dependent ...

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    14. Real-time processing for frequency domain optical imaging based on field programmable gated arrays

      Real-time processing for frequency domain optical imaging based on field programmable gated arrays

      Fequency domain optical imaging (OFDI) provides high resolution and sensitivity. However, the speed of the data processing program in C language limits its application. A real-time imaging system of OFDI based on field programmable gate arrays (FPGAs) is proposed. It adopts a high-speed digitizer board PXI14400 from Signatec for interferometric data acquisition. The acquired data is processed in the user defined FPGA on board in real-time with a pipeline data processing algorithm. The algorithm eliminates the complex conjugate ambiguity, overcomes the swept laser source’s nonlinearity in k -space, and allows the data to be processed continuously. We also provide ...

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      Mentions: Signatec
    15. Surface imaging of metallic material fractures using optical coherence tomography

      Surface imaging of metallic material fractures using optical coherence tomography

      We demonstrate the capability of optical coherence tomography (OCT) to perform topography of metallic surfaces after being subjected to ductile or brittle fracturing. Two steel samples, OL 37 and OL 52, and an antifriction Sn–Sb–Cu alloy were analyzed. Using an in-house-built swept source OCT system, height profiles were generated for the surfaces of the two samples. Based on such profiles, it can be concluded that the first two samples were subjected to ductile fracture, while the third one was subjected to brittle fracture. The OCT potential for assessing the surface state of materials after fracture was evaluated by ...

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    16. Optical coherence Doppler tomography for quantitative cerebral blood flow imaging

      Optical coherence Doppler tomography for quantitative cerebral blood flow imaging

      Optical coherence Doppler tomography (ODT) is a promising neurotechnique that permits 3D imaging of the cerebral blood flow (CBF) network; however, quantitative CBF velocity (CBFv) imaging remains challenging. Here we present a simple phase summation method to enhance slow capillary flow detection sensitivity without sacrificing dynamic range for fast flow and vessel tracking to improve angle correction for absolute CBFv quantification. Flow phantom validation indicated that the CBFv quantification accuracy increased from 15% to 91% and the coefficient of variation (CV) decreased 9.3-fold;in vivo mouse brain validation showed that CV decreased 4.4-/10.8- fold for venular ...

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    17. Ultra-compact silicon photonic integrated interferometer for swept-source optical coherence tomography

      Ultra-compact silicon photonic integrated interferometer for swept-source optical coherence tomography

      We demonstrate an ultra-compact silicon integrated photonic interferometer for swept-source optical coherence tomography (SS-OCT). The footprint of the integrated interferometer is only 0.75 × 5     mm 2 . The design consists of three 2 × 2 splitters, a 13 cm physical length (50.4 cm optical length) reference arm, and grating couplers. The photonic integrated circuit was used as the interferometer of an SS-OCT system. The sensitivity of the system was measured to be − 62     dB with 115 μW power delivered to the sample. Using the system, we demonstrate cross-sectional OCT imaging of a layered tissue phantom. We also discuss potential improvements ...

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    18. Scalable multiplexing for parallel imaging with interleaved optical coherence tomography

      Scalable multiplexing for parallel imaging with interleaved optical coherence tomography

      We demonstrate highly parallel imaging with interleaved optical coherence tomography (iOCT) using an in-house-fabricated, air-spaced virtually-imaged phased array (VIPA). The air-spaced VIPA performs spectral encoding of the interferograms from multiple lateral points within a single sweep of the source and allows us to tune and balance several imaging parameters: number of multiplexed points, ranging depth, and sensitivity. In addition to a thorough discussion of the parameters and operating principles of the VIPA, we experimentally demonstrate the effect of different VIPA designs on the multiplexing potential of iOCT. Using a 200-kHz light source, we achieve an effective A-scan rate of 3 ...

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    19. True color scanning laser ophthalmoscopy and optical coherence tomography handheld probe

      True color scanning laser ophthalmoscopy and optical coherence tomography handheld probe

      Scanning laser ophthalmoscopes (SLOs) are able to achieve superior contrast and axial sectioning capability compared to fundus photography. However, SLOs typically use monochromatic illumination and are thus unable to extract color information of the retina. Previous color SLO imaging techniques utilized multiple lasers or narrow band sources for illumination, which allowed for multiple color but not “true color” imaging as done in fundus photography. We describe the first “true color” SLO, handheld color SLO, and combined color SLO integrated with a spectral domain optical coherence tomography (OCT) system. To achieve accurate color imaging, the SLO was calibrated with a color ...

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    20. Coherent signal composition and global phase determination in signal multiplexed polarization sensitive optical coherence tomography

      Coherent signal composition and global phase determination in signal multiplexed polarization sensitive optical coherence tomography

      We present an analysis of the structural image information acquired with polarization sensitive optical coherence tomography (PS-OCT). In PS-OCT a total of four channels of data are acquired: two orthogonal polarization state components for each of two incident polarization states by which the sample is interrogated. Up to recently, the structural information of the sample was obtained by incoherent summation of these four channels. The four channels can be represented as a Jones matrix for each data point acquired from a sample. We show that the Signal to Noise ratio of the structural information can be improved by 2.3 ...

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    21. Real-time dispersion-compensated image reconstruction for compressive sensing spectral domain optical coherence tomography

      Real-time dispersion-compensated image reconstruction for compressive sensing spectral domain optical coherence tomography

      In this work, we propose a novel dispersion compensation method that enables real-time compressive sensing (CS) spectral domain optical coherence tomography (SD OCT) image reconstruction. We show that dispersion compensation can be incorporated into CS SD OCT by multiplying the dispersion-correcting terms by the undersampled spectral data before CS reconstruction. High-quality SD OCT imaging with dispersion compensation was demonstrated at a speed in excess of 70 frames per s using 40% of the spectral measurements required by the well-known Shannon/Nyquist theory. The data processing and image display were performed on a conventional workstation having three graphics processing units.

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    22. Fully automated side branch detection in intravascular optical coherence tomography pullback runs

      Fully automated side branch detection in intravascular optical coherence tomography pullback runs

      Side branches in the atherosclerotic lesion region are important as they highly influence the treatment strategy selection and optimization. Moreover, they are reliable landmarks for image registration. By providing high resolution delineation of coronary morphology, intravascular optical coherence tomography (IVOCT) has been increasingly used for side branch analysis. This paper presents a fully automated method to detect side branches in IVOCT images, which relies on precise segmentation of the imaging catheter, the protective sheath, the guide wire and the lumen. 25 in-vivo data sets were used for validation. The intraclass correlation coefficient between the algorithmic results and manual delineations for ...

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    23. Dual modality optical coherence and whole-body photoacoustic tomography imaging of chick embryos in multiple development stages

      Dual modality optical coherence and whole-body photoacoustic tomography imaging of chick embryos in multiple development stages

      Chick embryos are an important animal model for biomedical studies. The visualization of chick embryos, however, is limited mostly to postmortem sectional imaging methods. In this work, we present a dual modality optical imaging system that combines swept-source optical coherence tomography and whole-body photoacoustic tomography, and apply it to image chick embryos at three different development stages. The explanted chick embryos were imaged in toto with complementary contrast from both optical scattering and optical absorption. The results serve as a prelude to the use of the dual modality system in longitudinal whole-body monitoring of chick embryos in ovo .

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    24. Three-dimensional optical coherence micro-elastography of skeletal muscle tissue

      Three-dimensional optical coherence micro-elastography of skeletal muscle tissue

      In many muscle pathologies, impairment of skeletal muscle function is closely linked to changes in the mechanical properties of the muscle constituents. Optical coherence micro-elastography (OCME) uses optical coherence tomography (OCT) imaging of tissue under a quasi-static, compressive mechanical load to map variations in tissue mechanical properties on the micro-scale. We present the first study of OCME on skeletal muscle tissue. We show that this technique can resolve features of muscle tissue including fibers, fascicles and tendon, and can also detect necrotic lesions in skeletal muscle from the mdx mouse model of Duchenne muscular dystrophy. In many instances, OCME provides ...

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    1-24 of 1114 1 2 3 4 ... 45 46 47 »
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