1. Articles from Shuichi Makita

    49-72 of 86 « 1 2 3 4 »
    1. Complex Conjugate Resolved Retinal Imaging by One-micrometer Spectral Domain Optical Coherence Tomography Using an Electro-optical Phase Modulator

      Complex Conjugate Resolved Retinal Imaging by One-micrometer Spectral Domain Optical Coherence Tomography Using an Electro-optical Phase Modulator
      Full-range spectral domain optical coherence tomography (SD-OCT) with a 1-μm band light source is shown here. The phase of the reference beam is continuously stepped while the probing beam scans the sample laterally (B-scan). The two dimensional spectral interferogram obtained is processed by a Fourier transform method to obtain a complex spectrum leading to a full-range OCT image. A detailed mathematical explanation of the complex conjugate resolving method utilized is provided. The system’s measurement speed was 7.96 kHz, the measured axial resolution was 9.6 μm in air and the maximum sensitivity 99.4 dB. To demonstrate the ...
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    2. Choroidal thickness measurement in healthy Japanese subjects by three-dimensional high-penetration optical coherence tomography

      Choroidal thickness measurement in healthy Japanese subjects by three-dimensional high-penetration optical coherence tomography

      Background We performed retinal and choroidal thickness mapping by three-dimensional high-penetration optical coherence tomography (OCT) and evaluated the choroidal thickness distribution throughout the macula in healthy eyes. Methods Forty-three eyes of 43 healthy Japanese volunteers were evaluated by 1060-nm swept-source OCT. The eyes were scanned with a three-dimensional raster scanning protocol, and the mean retinal and choroidal thicknesses of the posterior sectors were obtained. The sectors were defined by the Early Treatment Diabetic Study (ETDRS) layout. These data were compared by age (23–56 years), spherical equivalent refractive error (between +0.9 D and −10.3 D), and axial length ...

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    3. Enhanced imaging of choroidal vasculature by high-penetration and dual-velocity optical coherence angiography

      Enhanced imaging of choroidal vasculature by high-penetration and dual-velocity optical coherence angiography
      Dual-beam-scan Doppler optical coherence angiography (DB-OCA) with a 1-μm-wavelength probe is demonstrated for improved in vivo choroidal angiograms of the human eye. This method utilizes two scanning beams with spatial and temporal separation on the retina, and provides two measurable velocity ranges. The method achieves higher sensitivity to very low velocity flows than conventional Doppler optical coherence tomography. Moreover, longer wavelengths allowing greater penetration, enhanced visualization of choroidal vessels is verified with en-face projection images of the Doppler shift squared. Specifically, better choroidal vasculature visibility is achieved at a wavelength of 1 μm than at 840 nm.
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    4. Fast retinal layer identification for optical coherence tomography images

      Fast retinal layer identification for optical coherence tomography images

      Fast method for identifying the internal limiting membrane (ILM) and retinal pigment epithelium (RPE) from optical coherence tomography images is demonstrated. To avoid unnecessary increment of calculation time, a strong downsampling of the original data set is performed to reduce a number of processed pixels. In ILM segmentation, the obtained data cube is filtered with two different kinds of parameters and two estimates for the position of ILM is determined. A simple smoothness value is determined for both estimates and better estimate is used for future processing. A smaller portion of pixels around estimated ILM are extracted from the down ...

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    5. Three-dimensional visualization of ocular vascular pathology by optical coherence angiography in vivo

      Three-dimensional visualization of ocular vascular pathology by optical coherence angiography in vivo
      Purpose: To demonstrate the clinical application of a noninvasive, three-dimensional vascular-imaging technique called “Doppler optical coherence angiography (OCA)”. To evaluate the vascular architecture of polypoidal choroidal vasculopathy (PCV) using Doppler OCA. Methods: We prospectively examined the eyes of 4 healthy subjects and 15 PCV patients. Three-dimensional vascular-flow imaging was performed using high-speed, high-resolution, and high-penetration spectral-domain Doppler optical coherence tomography. Two-dimensional images of the retina, choroid, and vascular lesions were obtained simultaneously. Results: Distribution of blood flow detected by Doppler OCA imaging corresponded well with that by indocyanine angiographic imaging. PCV lesions were localized in the space between the retinal ...
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    6. Comprehensive in vivo micro-vascular imaging of the human eye by dual-beam-scan Doppler optical coherence angiography

      Comprehensive in vivo micro-vascular imaging of the human eye by dual-beam-scan Doppler optical coherence angiography
      Comprehensive angiography provides insight into the diagnosis of vascular-related diseases. However, complex microvascular networks of unstable in vivo organs such as the eye require micron-scale resolution in three dimensions and a high sampling rate to access a wide area as maintaining the high resolution. Here, we introduce dual-beam-scan Doppler optical coherence angiography (OCA) as a label-free comprehensive ophthalmic angiography that satisfies theses requirements. In addition to high resolution and high imaging speed, high sensitivity to motion for detecting tiny blood flow of microvessels is achieved by detecting two time-delayed signals with scanning of two probing beams separated on a sample ...
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    7. Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography

      Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography
      Polarization-sensitive optical coherence tomography (PS-OCT) is known to be advantageous because of its additional tissue-specific contrast of the anterior eye. So far, this advantage has been shown only qualitatively. We evaluate the improved visibility afforded by 3-D PS corneal and anterior eye segment OCT (PS-CAS-OCT) in visualizing the trabecular meshwork (TM) based on statistical evidences. A total of 31 normal subjects participated in this study. The anterior eye segments of both the eyes of the subjects are scanned using a custom-made PS-CAS-OCT and the standard-scattering OCT (S-OCT) and polarization-sensitive phase-retardation OCT (P-OCT) images are obtained. Three graders grade the visibility ...
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    8. Wettability characterization method based on optical coherence tomography imaging

      Wettability characterization method based on optical coherence tomography imaging
      A novel method for surface wetting characterization based on contact angle measurements is presented. Three dimensional structural imaging of a droplet on a substrate is performed using optical coherence tomography (OCT) which provides micrometer resolution images without contact with the sample. An automatic OCT intensity variation based, layer segmentation method was implemented to identify air-droplet, droplet-substrate and air-substrate interfaces. A glycerol droplet on a rough tilted glass substrate was used as a test sample to demonstrate the applicability of the proposed method for wetting characterization. Results show that the contact angle of any observation angle can be obtained. In addition ...
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    9. Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation

      Full-range polarization-sensitive swept-source optical coherence tomography by simultaneous transversal and spectral modulation
      Polarization-sensitive swept-source optical coherence tomography (PS-SS-OCT) is used to measure three-dimensional phase-retardation images of birefringent biological tissue in vivo. PS-SS-OCT with continuous source polarization modulation is used to multiplex the incident states of polarization in the signal frequency of each A-scan. Although it offers the advantage of measurement speed that is as high as that of standard SS-OCT, its disadvantage is low axial measurement range. To overcome this drawback, we employed the B-M-mode scan (BM-scan) method, which removes complex conjugate ambiguity by applying phase modulation along the transversal scanning direction. Since polarization modulation and BM-scan are applied in different scanning ...
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    10. Simultaneous high-resolution retinal imaging and high-penetration choroidal imaging by one-micrometer adaptive optics optical coherence tomography

      Simultaneous high-resolution retinal imaging and high-penetration choroidal imaging by one-micrometer adaptive optics optical coherence tomography
      Adaptive optics optical coherence tomography (AO-OCT) provides three-dimensional high-isotropic-resolution retinal images in vivo. We developed AO-OCT with a 1.03-μm probing beam and demonstrated high-penetration, high-resolution retinal imaging. Axial scans are acquired with a speed of 47,000 lines/s. AO closed loop is configured with a single deformable mirror. Seven eyes of 7 normal subjects were examined. Signal enhancement was found for all subjects. A rippled interface between nerve fiber layer and ganglion cell layer, boundary between ganglion cell layer and inner plexiform layer, and chorioscleral interface were identified. Simultaneous high-resolution and high-penetration choroidal imaging may be useful for ...
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    11. High-sensitive blood flow imaging of the retina and choroid by using double-beam optical coherence angiography

      High-sensitive blood flow imaging of the retina and choroid by using double-beam optical coherence angiography
      Wide-field and high-sensitive Doppler optical coherence angiography of the posterior human eye has been demonstrated. High-sensitive phase-resolved spectral-domain optical coherence tomography using the superluminescent diode with the central wavelength of 840 nm and bandwidth of 50 nm (FWHM) is developed. Two OCT signals with a time separation are acquired simultaneously with double sampling beams divided by using a Wollaston prism and a polarization-sensitive spectrometer consisting of two line scan cameras. The total power of two beams on the cornea is 700 µW. The line scan rate of cameras is 27 kHz and each OCT channel has the sensitivity of 93 ...
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    12. Tissue discrimination in anterior eye using three optical parameters obtained by polarization sensitive optical coherence tomography

      Tissue discrimination in anterior eye using three optical parameters obtained by polarization sensitive optical coherence tomography
      A tissue discrimination algorithm of polarization sensitive optical coherence tomography (PS-OCT) based on optical properties of tissue was developed. We calculated three dimensional (3D) feature vector (intensity, extinction coefficient, birefringence) obtained by PS-OCT. The tissue types of each pixel were discriminated according to positions of the feature vectors in 3D feature space. This algorithm was applied for discrimination of human anterior eye chamber. Conjunctiva, selera, trabecular meshwork (TM), cornea and uvea were well separated in the 3D feature space and discriminated in good contrast
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    13. Adaptive optics spectral domain optical coherence tomography with one-micrometer light source

      Adaptive optics spectral domain optical coherence tomography with one-micrometer light source
      Adaptive optics spectral domain optical coherence tomography (AO SD-OCT) has provided three-dimensional high isotropic resolution retinal images in vivo. In order to enhance the image quality of deep region of the eye, the alternative wavelength of 1-µm has been used for ophthalmic OCT. This study aims to develop AO SD-OCT with one-micrometer probe and demonstrated high penetration and high resolution retinal imaging. A broadband 1-µm SLD light source (Suplerlum) have the center wavelength of 1.03 µm and the spectral bandwidth of 106 nm. Axial scans were obtained by an InGaAs line scan camera with the speed of 47,000 ...
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    14. Adaptive optics retinal scanner for one-micrometer light source

      Adaptive optics retinal scanner for one-micrometer light source
      We developed an adaptive optics (AO) retinal scanner by using a light source with a center wavelength of 1-um. In a recent study on optical coherence tomography (OCT), it was proved that 1-um light provided higher image contrast of deep region of the eye than 840-nm light. Further, high lateral resolution retinal images were obtained with AO. In this study, we performed measurements on two normal subjects in the AO-SLO mode and analyzed its performance toward developing the AO-OCT. With AO correction, we found that the residual RMS wavefront error of ocular aberration was less than 0.1 μm. We ...
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    15. Parabolic BM-scan technique for full range Doppler spectral domain optical coherence tomography

      Parabolic BM-scan technique for full range Doppler spectral domain optical coherence tomography
      A full range spectral domain optical coherence tomography (SD-OCT) technique that relies on the linear phase modulation of one of the interferometer arms has been widely utilized. Although this method is useful, the mirror image elimination is not perfect for samples in which regions with high axial motion exist. In this paper, we introduce a new modulation pattern to overcome this mirror image elimination failure. This new modulation is a parabolic phase modulation in the transverse scanning direction, and is applied to the SD-OCT reference beam by an electro-optic modulator. Flow phantom and in vivo experiments demonstrate that for moving ...
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    16. Generalized Jones matrix optical coherence tomography: performance and local birefringence imaging

      Generalized Jones matrix optical coherence tomography: performance and local birefringence imaging
      Phase retardation imaging including local birefringence imaging of biological tissues is described by generalized Jones-matrix optical coherence tomography. The polarization properties of a local tissue can be obtained from two Jones matrices that are measured by backscattered lights from the front and back boundaries of the local tissue. The error in the phase retardation measurement due to background noise is analyzed theoretically, numerically, and experimentally. The minimum detectable phase retardation is estimated from numerical simulations. The theoretical analysis suggests that the measurements with two orthogonal input polarization states have the lowest retardation error. Local birefringence imaging is applied to the ...
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    17. Tissue discrimination in anterior eye using three optical parameters obtainedby polarization sensitive optical coherence tomography

      Tissue discrimination in anterior eye using three optical parameters obtainedby polarization sensitive optical coherence tomography

      We developed a tissue discrimination algorithm of polarization sensitive optical coherence tomography (PS-OCT) based on the optical properties of tissues. We calculated the three-dimensional (3D) feature vector from the parameters intensity, extinction coefficient, birefringence, which were obtained by PS-OCT. The tissue type of each pixel was determined according to the position of the feature vector in the 3D feature space. The algorithm was applied for discriminating tissues of the human anterior eye segment. The conjunctiva, sclera, trabecular meshwork (TM), cornea, and uvea were well separated in the 3D feature space, and we observed them with good contrast. The TM line ...

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    18. Automated segmentation of the macula by optical coherence tomography

      Automated segmentation of the macula by optical coherence tomography
      This paper presents optical coherence tomography (OCT) signal intensity variation based segmentation algorithms for retinal layer identification. Its main ambition is to reduce the calculation time required by layer identification algorithms. Two algorithms, one for the identification of the internal limiting membrane (ILM) and the other for retinal pigment epithelium (RPE) identification are implemented to evaluate structural features of the retina. Using a 830 nm spectral domain OCT device, this paper demonstrates a segmentation method for the study of healthy and diseased eyes.
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    19. Visualization of phase retardation of deep posterior eye by polarization-sensitive swept-source optical coherence tomography with1-µm probe

      Visualization of phase retardation of deep posterior eye by polarization-sensitive swept-source optical coherence tomography with1-µm probe
      Polarization-sensitive optical coherence tomography (PS-OCT) can measure cross-sectional and volumetric images of birefringence in fibrous tissues that provides additional contrast to the intensity images. In this study, we develop polarization-sensitive swept-source OCT (PS-SSOCT) at 1 μm for deep penetration of the sclera and lamina cribrosa in the posterior part of human eyes. A calibration method for polarization mode dispersion of a circulator, which is employed to conserve the optical power of the interferometer and achieve system sensitivity sufficient for retinal imaging is demonstrated. The A-scan rate, the axial resolution, and the sensitivity of the PS-SS-OCT are 28,000 Hz, 11 ...
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    20. Optical coherence angiography for the eye

      Optical coherence angiography for the eye
      A new technique for monitoring blood flow will help investigate eye functions and retinal disease. Poor blood supply is one of the main causes of several retinal diseases. Vascular disorders and impaired circulation are observed in major eye diseases that cause blindness, including age-related macular degeneration (AMD)1 and glaucoma.2 A noninvasive, 3D imaging tool for major vascular systems of the eye might be helpful for understanding and diagnosing eye diseases. Circulation abnormalities are typically diagnosed using fluorescence angiography, in which injected fluorescent dye is detected. However, this technique is invasive, may have side effects, and cannot be used ...
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    21. Multifunctional optical imaging reveals tissue properties of the anterior eye

      Multifunctional optical imaging reveals tissue properties of the anterior eye
      A combination of polarization and Doppler-flow imaging for optical coherence tomography enhances image contrast without sacrificing acquisition speeds. Corneal and anterior-segment optical coherence tomography (CAS-OCT) is an imaging mode used to obtain cross-sectional images of the anterior eye segment in a noncontact and noninvasive manner.1 CAS-OCT has been used in clinics for diagnosis and basic research of ocular diseases such as glaucoma. Although conventional OCT helps to visualize the distribution of backscattering intensities from tissues, unlike histological techniques it does not guarantee clear differentiation of individual tissues. To enhance the contrast of OCT images, the birefringence and Doppler flow ...
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    22. In vivo depth-resolved tissue contrast by local birefringence and differential optic axis orientation using polarization-sensitive swept-source optical coherence tomography

      Depth-resolved tissue contrast imaging using local polarization properties has been demonstrated in vivo with fiber-based polarization-sensitive swept-source optical coherence tomography. The local birefringence and differential optic axis orientation are calculated with an algorithm based on Jones ... [Proc. SPIE 7168, 71682H (2009)] published Fri Feb 20, 2009.
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    23. Automated retinal pigment epithelium identification from optical coherence tomography images

      Simple and robust method for identifying the retinal pigment epithelium (RPE) from optical coherence tomography images is demonstrated. At first, the maximum intensity value of each A-scans were determined and the depth position of those pixels are identified. The obtained 2D matrix is used as first ... [Proc. SPIE 7168, 716827 (2009)] published Fri Feb 20, 2009.
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    49-72 of 86 « 1 2 3 4 »
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    1. (85 articles) University of Tsukuba
    2. (85 articles) Yoshiaki Yasuno
    3. (84 articles) Shuichi Makita
    4. (34 articles) Masahiro Miura
    5. (25 articles) Masahiro Yamanari
    6. (20 articles) Tokyo Medical University
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    Automated segmentation of the macula by optical coherence tomography Tissue discrimination in anterior eye using three optical parameters obtainedby polarization sensitive optical coherence tomography Parabolic BM-scan technique for full range Doppler spectral domain optical coherence tomography Visibility of trabecular meshwork by standard and polarization-sensitive optical coherence tomography Enhanced imaging of choroidal vasculature by high-penetration and dual-velocity optical coherence angiography Optoretinography: optical measurements of human cone and rod photoreceptor responses to light Nodular skin lesions: correlation of reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) features OCT and Ophthalmology in the Age of Artificial Intelligence, Tuesday Oct 8, 2019 1:00P EDT Compensation for the Influence of Fluctuations in the Distance to the Object During Noncontact Probing in Spectral Domain Optical Coherence Tomography Pattern electroretinogram changes in patients with primary open-angle glaucoma in correlation with visual field and optical coherence tomography changes Objective evaluation of proliferative diabetic retinopathy using optical coherence tomography Repeatability of Cornea and Sublayer Thickness Measurements Using Optical Coherence Tomography in Corneas of Anomalous Refractive Status