1. Articles from Jin U. Kang

    1-24 of 102 1 2 3 4 5 »
    1. CNN-based CP-OCT sensor integrated with a subretinal injector for retinal boundary tracking and injection guidance

      CNN-based CP-OCT sensor integrated with a subretinal injector for retinal boundary tracking and injection guidance

      Significance: Subretinal injection is an effective way of delivering transplant genes and cells to treat many degenerative retinal diseases. However, the technique requires high-dexterity and microscale precision of experienced surgeons, who have to overcome the physiological hand tremor and limited visualization of the subretinal space. Aim: To automatically guide the axial motion of microsurgical tools (i.e., a subretinal injector) with microscale precision in real time using a fiber-optic common-path swept-source optical coherence tomography distal sensor. Approach: We propose, implement, and study real-time retinal boundary tracking of A-scan optical coherence tomography (OCT) images using a convolutional neural network (CNN) for ...

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    2. Stabilizing the phase of swept-source optical coherence tomography by a wrapped Gaussian mixture model

      Stabilizing the phase of swept-source optical coherence tomography by a wrapped Gaussian mixture model

      The phase of an optical coherence tomography (OCT) signal carries critical information about particle micro-displacements. However, swept-source OCT (SSOCT) suffers from phase instability problems due to trigger jitters from the swept source. In this Letter, a wrapped Gaussian mixture model (WGMM) is proposed to stabilize the phase of SSOCT systems. A closed-form iteration solution of the WGMM is derived using the expectation-maximization algorithm. Necessary approximations are made for real-time graphic processing unit implementation. The performance of the proposed method is demonstrated through ex vivo, in vivo, and flow phantom experiments. The results show the robustness of the method in different ...

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    3. Optical flow optical coherence tomography for determining accurate velocity fields

      Optical flow optical coherence tomography for determining accurate velocity fields

      Determining micron-scale fluid flow velocities using optical coherence tomography (OCT) is important in both biomedical research and clinical diagnosis. Numerous methods have been explored to quantify the flow information, which can be divided into either phase-based or amplitude-based methods. However, phase-based methods, such as Doppler methods, are less sensitive to transverse velocity components and suffer from wrapped phase and phase instability problems for axial velocity components. On the other hand, amplitude-based methods, such as speckle variance OCT, correlation mapping OCT and split-spectrum amplitude-decorrelation angiography, focus more on segmenting flow areas than quantifying flow velocities. In this paper, we propose optical ...

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    4. Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control

      Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control

      Significance: Selective retina therapy (SRT) selectively targets the retinal pigment epithelium (RPE) and reduces negative side effects by avoiding thermal damages of the adjacent photoreceptors, the neural retina, and the choroid. However, the selection of proper laser energy for the SRT is challenging because of ophthalmoscopically invisible lesions in the RPE and different melanin concentrations among patients or even regions within an eye. Aim: We propose and demonstrate SRT monitoring based on speckle variance optical coherence tomography (svOCT) for dosimetry control. Approach: M-scans, time-resolved sequence of A-scans, of ex vivo bovine retina irradiated by 1.7-μs duration laser pulses ...

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    5. Intraoperative Speckle Variance Optical Coherence Tomography for Tissue Temperature Monitoring During Cutaneous Laser Therapy

      Intraoperative Speckle Variance Optical Coherence Tomography for Tissue Temperature Monitoring During Cutaneous Laser Therapy

      Background: Tissue temperature monitoring during cutaneous laser therapy can lead to safer and more effective treatments. In this study, we investigate the use of speckle variance optical coherence tomography (svOCT) to monitor real-time temperature changes in the excised human skin tissue sample during laser irradiation. Methods: To accomplish this, we combined the pulse laser system with a reference-based svOCT system. To calibrate the svOCT, the ex-vivo human skin samples from three individuals with tissues collected from the arm, face, and back were heated with 1-degree increments. Additionally, linear regression was used to extract and evaluate the linear relationship between the ...

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    6. Ophthalmic laser system integrated with speckle variance optical coherence tomography for real-time temperature monitoring

      Ophthalmic laser system integrated with speckle variance optical coherence tomography for real-time temperature monitoring

      A commercial ophthalmic laser system (R;GEN, Lutronic Corp) was integrated with a swept-source optical coherence tomography (OCT) imaging system for real-time tissue temperature monitoring. M-scan OCT images were acquired during laser-pulse radiation, and speckle variance OCT (svOCT) images were analyzed to deduce temporal signal variations related to tissue temperature change from laser-pulse radiation. A phantom study shows that svOCT magnitude increases abruptly after laser pulse radiation and recovered exponentially, and the peak intensity of svOCT image was linearly dependent on pulse laser energy until it saturates. A study using bovine iris also showed signal variation dependence on the laser ...

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    7. Motion-compensated optical coherence tomography using envelope-based surface detection and Kalman-based prediction

      Motion-compensated optical coherence tomography using envelope-based surface detection and Kalman-based prediction

      We present an optical coherence tomography (OCT) imaging system that effectively compensates unwanted axial motion with micron-scale accuracy. The OCT system is based on a swept-source (SS) engine (1060-nm center wavelength, 100-nm full-width sweeping bandwidth, and 100-kHz repetition rate), with axial and lateral resolutions of about 4.5 and 8.5 microns respectively. The SS-OCT system incorporates a distance sensing method utilizing an envelope-based surface detection algorithm. The algorithm locates the target surface from the B-scans, taking into account not just the first or highest peak but the entire signature of sequential A-scans. Subsequently, a Kalman filter is applied as ...

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    8. Feasibility study: protein denaturation and coagulation monitoring with speckle variance optical coherence tomography

      Feasibility study: protein denaturation and coagulation monitoring with speckle variance optical coherence tomography

      We performed the feasibility study using speckle variance optical coherence tomography (SvOCT) to monitor the thermally induced protein denaturation and coagulation process as a function of temperature and depth. SvOCT provided the depth-resolved image of protein denaturation and coagulation with microscale resolution. This study was conducted using egg white. During the heating process, as the temperature increased, increases in the speckle variance signal was observed as the egg white proteins coagulated. Additionally, by calculating the cross-correlation coefficient in specific areas, denaturized egg white conditions were successfully estimated. These results indicate that SvOCT could be used to monitor the denaturation process ...

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    9. Optical coherence tomography systems and methods with magnitude and direction tracking of transverse motion

      Optical coherence tomography systems and methods with magnitude and direction tracking of transverse motion

      An optical coherence tomography (OCT) system having magnitude and direction of motion detection has a light source, and a scanning system arranged in an optical path of the light source. The scanning system is configured to scan an illumination beam of light in a spatial pattern around each of a plurality of points of interest of an object under observation for a corresponding plurality of instants of time in which each of the plurality of points of interest are displaced from each other due to motion of at least one of the OCT system or the object under observation. The ...

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    10. Ghost Reduction in CP-SSOCT Having Multiple References Using Fourier-Domain Shift and Sum

      Ghost Reduction in CP-SSOCT Having Multiple References Using Fourier-Domain Shift and Sum

      We propose, test, and validate a novel Fourier-domain-based method for ghost image artifacts reduction in a common-path SSOCT system having multiple adjacent reference planes. Common-path probes with imaging systems containing high-index sapphire ball or other lenses produce multiple fixed references due to Fresnel reflections from the lens surfaces. The multiple reference planes produce multiple and overlapping optical coherence tomography (OCT) images. Since such ghost artifacts are the result of the superposition of multiple identical images having different amplitudes and spatial shifts, one can correctly shift and sum the images in the Fourier-domain once the relative amplitude and lateral position between ...

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    11. Active depth-guding handheld micro-forceps for membranectomy based on CP-SSOCT

      Active depth-guding handheld micro-forceps for membranectomy based on CP-SSOCT

      In this study, we demonstrate a handheld motion-compensated micro-forceps system using common-path swept source optical coherence tomography with highly accurate depth-targeting and depth-locking for Epiretinal Membrane Peeling. Two motors and a touch sensor were used to separate the two independent motions: motion compensation and tool-tip manipulation. A smart motion monitoring and guiding algorithm was devised for precise and intuitive freehand control. Ex-vivo bovine eye experiments were performed to evaluate accuracy in a bovine retina retinal membrane peeling model. The evaluation demonstrates system capabilities of 40 um accuracy when peeling the epithelial layer of bovine retina.

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    12. Lateral distortion corrected optical coherence tomography system

      Lateral distortion corrected optical coherence tomography system

      A lateral-distortion corrected optical coherence tomography system. The system can include an optical coherence tomography sensor, a light source, a fiber-optic system arranged to provide a reference beam and an observation beam, an optical detection system arranged to receive combined light from the reference beam and the observation beam and to provide detection signals, and a data processing system arranged to communicate with the optical detection system and receive the detection signals. The data processing system can be configured to assemble an image corresponding to a scanning path by constructing a plurality of A-scans from the detection signals, determining displacement ...

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    13. Interferometric force sensor for surgical instruments

      Interferometric force sensor for surgical instruments

      A surgical tool system according to an embodiment of the current invention includes a surgical tool, and an interferometry system optically coupled to the surgical tool. The surgical tool includes a body section, a sensor section at least one of attached to or integral with the body section, and a surgical section at least one of attached to or integral with the sensor section at an opposing end of the sensor section from the body section. The sensor section comprises an interferometric optical sensor defining a reference distance that changes in response to at least one of a force or ...

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    14. Distortion corrected optical coherence tomography system

      Distortion corrected optical coherence tomography system

      An axial motion distortion-corrected optical coherence tomography system. The system can include an optical coherence tomography sensor, a light source, a fiber-optic system arranged to provide a reference beam and an observation beam, an optical detection system arranged to receive combined light from the reference beam and the observation beam and to provide detection signals, and a data processing system arranged to receive said detection signals, construct a plurality of A-scans from said detection signals, and construct one or more images from said plurality of A-scans. The data processing system can be configured to correct distortion in the images caused ...

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    15. Durable single mode fiber probe with optimized reference reflectivity

      Durable single mode fiber probe with optimized reference reflectivity

      A probe for a common path optical coherence tomography system includes a sheath having a proximal end and a distal end and defining a lumen therein, a single mode optical fiber disposed within the lumen of the sheath such that a portion of the single mode optical fiber extends beyond the distal end of the sheath. The single mode optical fiber has an end face for transmitting and receiving light. The probe also includes a layer of hardened epoxy encasing the portion of the single mode optical fiber that extends beyond the distal end of the sheath except for the ...

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    16. Fiber Optic Distal Sensor Controlled MICRO-MANIPULATION Systems And Methods

      Fiber Optic Distal Sensor Controlled MICRO-MANIPULATION Systems And Methods

      A motion-compensated cutting system includes a hand-held tool body, and an actuator connected to the tool body. A shaft of the actuator is movable relative to the tool body so that a distal end of a cutting implement attached to the shaft is axially movable relative to the tool body. An optical coherence tomography system includes an optical fiber with a distal end fixed relative to the distal end of the cutting implement. The system includes a control unit that can determine a position of the distal end of the cutting implement relative to a reference surface based on input ...

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    17. Motion-compensated optical coherence tomography system

      Motion-compensated optical coherence tomography system

      A motion-compensated optical coherence tomography system includes an optical coherence tomography sensor that includes a common-path optical fiber having an end for emitting light, reflecting reference light and receiving returned light for detection; a motion-compensation system attached to the common-path optical fiber and operable to move at least a portion of the optical fiber so as to compensate for motion between the end of the common-path optical fiber and an object being imaged; and a feedback control system configured to communicate with the optical coherence tomography sensor and the motion-compensation system. The feedback control system is configured to receive information ...

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    18. Accurate real-time depth control for CP-SSOCT distal sensor based handheld microsurgery tools

      Accurate real-time depth control for CP-SSOCT distal sensor based handheld microsurgery tools

      This paper presents a novel intuitive targeting and tracking scheme that utilizes a common-path swept source optical coherence tomography (CP-SSOCT) distal sensor integrated handheld microsurgical tool. To achieve micron-order precision control, a reliable and accurate OCT distal sensing method is required; simultaneously, a prediction algorithm is necessary to compensate for the system delay associated with the computational, mechanical and electronic latencies. Due to the multi-layered structure of retina, it is necessary to develop effective surface detection methods rather than simple peak detection. To achieve this, a shifted cross-correlation method is applied for surface detection in order to increase robustness and ...

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    19. Sapphire lens-based optical fiber probe for optical coherence tomography

      Sapphire lens-based optical fiber probe for optical coherence tomography

      A probe for an optical coherence tomography system according to an embodiment of the current invention includes a sheath having a proximal end and a distal end and defining a lumen therein, an optical fiber disposed at least partially within the lumen of said sheath, and a sapphire lens attached to the distal end of the sheath to form a fluid-tight seal to prevent fluid from entering the lumen of said sheath. The optical fiber has an end arranged in an optical path with the sapphire lens to provide optical coupling between the sapphire lens and the optical fiber.

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    20. Real-time 3D and 4D fourier domain doppler optical coherence tomography system

      Real-time 3D and 4D fourier domain doppler optical coherence tomography system

      An optical coherence tomography imaging system includes a Fourier domain optical coherence tomography sensor system, a signal processing system configured to communicate with the Fourier domain optical coherence tomography sensor system to receive detection signals therefrom and to provide imaging signals, and an image display system configured to communicate with the signal processing system to receive the imaging signals. The signal processing system includes a parallel processor configured to calculate structure information and Doppler information from the detection signals in real time such that the imaging signals provide a real time display of combined structure and flow of an object ...

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    21. Two-dimensional compressive sensing in spectral domain optical coherence tomography

      Two-dimensional compressive sensing in spectral domain optical coherence tomography

      In this paper, we proposed a novel compressive sensing (CS) method in spectral domain optical coherence tomography (SD OCT), which reconstructs B-scan image using a subset of the spectral data that is under-sampled in both axial and lateral dimensions. Thus a fraction of the A-scans for a B-scan are acquired; the spectral data of each acquired A-scan is under-sampled. Compared with the previous studies, our method further reduces the overall size of the spectral measurements. Experimental results show that our approach can obtain high quality B-scan image using 25% spectral data, which takes 50% number of A-scans and acquires 50 ...

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    22. Graphics processing unit-accelerated real-time compressive sensing spectral domain optical coherence tomography

      Graphics processing unit-accelerated real-time compressive sensing spectral domain optical coherence tomography

      In this paper, we systematically demonstrate two real-time CS SD OCT systems based on a conventional desktop having three GPUs. The first one takes fast Fourier transform (FFT) as the sensing technique and under-sampled linear wavenumber spectral sampling as input data, while the second one uses non-uniform fast Fourier transform (NUFFT) and under-sampled nonlinear wavenumber spectral sampling, respectively. The maximum reconstruction speed of 72k and 33.5k A-line/s were achieved for these two systems, respectively, with A-scan size 2048. It is >100 times faster than the C++ implementation and >400 times faster than the MATLAB implementation. Finally, we present ...

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    23. Injection-depth-locking axial motion guided handheld micro-injector using CP-SSOCT

      Injection-depth-locking axial motion guided handheld micro-injector using CP-SSOCT

      This paper presents a handheld micro-injector system using common-path swept source optical coherence tomography (CP-SSOCT) as a distal sensor with highly accurate injection-depth-locking. To achieve real-time, highly precise, and intuitive freehand control, the system used graphics processing unit (GPU) to process the oversampled OCT signal with high throughput and a smart customized motion monitoring control algorithm. A performance evaluation was conducted with 60-insertions and fluorescein dye injection tests to show how accurately the system can guide the needle and lock to the target depth. The evaluation tests show our system can guide the injection needle into the desired depth with ...

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    24. Postdoctoral position in Photonics and Optoelectronics at Johns Hopkins University

      Postdoctoral position in Photonics and Optoelectronics at Johns Hopkins University

      The Photonics and Optoelectronics Laboratory at the Johns Hopkins University is seeking outstanding candidates for a post-doctoral position in OCT area. Candidates with strong experimental background in optical coherence tomography with image processing are preferred. Candidates should have strong foundation in optical engineering, imaging, and mathematical methods. In addition, candidates should be experienced in computer programming and instrumentations. Candidates must hold PhD degree by July 1 2014. The successful applicant will work on development and application of high resolution, ultrafast optical coherence tomography for various medical applications. Applications can be submitted electronically as a single PDF document to: jkang@jhu ...

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    1-24 of 102 1 2 3 4 5 »
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