24 results on '"Cho, Nam Hyun"'
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2. Cochlear motion across the reticular lamina implies that it is not a stiff plate
- Author
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Cho, Nam Hyun and Puria, Sunil
- Published
- 2022
- Full Text
- View/download PDF
3. Differential transverse motion of individual outer hair cells measured in gerbil high-frequency region.
- Author
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Puria, Sunil, Cho, Nam Hyun, and Guinan, John
- Subjects
- *
HAIR cells , *GERBILS , *AUDIO frequency , *COCHLEA , *CYTOARCHITECTONICS - Abstract
The great sensitivity and frequency selectivity of mammalian hearing originates in the mechanical properties of the cochlea. Cochlear motions in response to sound are amplified using metabolic energy. The motor element of this cochlear amplification is presumed to be the outer hair cell (OHC), that expands and contracts lengthwise in response to a change in receptor potential at audio frequencies. How thousands of OHCs, acting through the local cytoarchitecture, work to achieve cochlear amplification is not fully understood. The properties of individual OHCs measured in micro-chamber environments are low-pass with a corner frequency of, at most, a few kHz. OHC corner frequencies within the cochlea have been estimated to be ∼3 kHz. Since in-vivo cochlear motion measurements show amplified frequency responses that extend up to many tens of kHz, but OHCs have corner frequencies of a few kHz, it has been suggested that OHCs are not active at the highest frequencies. How to reconcile these measurements has been a challenge. To address this, we made transverse cochlear motion measurements using a high-resolution optical-coherence-tomography (OCT) system at approximately the two ends of the OHC axial length: at the OHC bottom near the OHC-Deiter-Cell junction and at the OHC top near the reticular lamina. From these in-vivo measurements near the 42 kHz best frequency (BF) region of the gerbil cochlea, we determined the transverse differential response of OHCs. To remove phase from the traveling wave, we calculated the ratio of the RL motion to the motion at the OHC-Deiter-Cell junction. The OHC top-to-bottom phase difference was almost exactly ½-cycle at frequencies up to 35-40 kHz. As frequency increased above 40 kHz, the phase difference decreased until near BF there was very little phase difference. The OHC top-to-bottom amplitude ratio transitioned from the OHC top moving less than the bottom at low frequencies, to the OHC top moving more than the bottom, at about 30 kHz, which is approximately the frequency above which there is traveling-wave amplification. Our data show that OHCs had length changes at frequencies up to 50 kHz, more than a decade above their low-pass corner frequency in vitro. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
4. Quantitative assessment of touch-screen panel by nondestructive inspection with three-dimensional real-time display optical coherence tomography
- Author
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Cho, Nam Hyun, Park, Kibeom, Kim, Jae-Young, Jung, Yeongri, and Kim, Jeehyun
- Published
- 2015
- Full Text
- View/download PDF
5. Development of mechanistic–empirical design method for an asphalt pavement rutting model using APT
- Author
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Suh, Young-Chan, Cho, Nam-Hyun, and Mun, Sungho
- Published
- 2011
- Full Text
- View/download PDF
6. Development of a rutting performance model for asphalt concrete pavement based on test road and accelerated pavement test data
- Author
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Suh, Young-Chan and Cho, Nam-Hyun
- Published
- 2014
- Full Text
- View/download PDF
7. Development of Korea Airport Pavement Condition Index for Panel Rating.
- Author
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Cho, Nam-Hyun, Kwon, Hong-Joon, Suh, Young-Chan, and Kim, Jangrak
- Subjects
PAVEMENT maintenance & repair ,PAVEMENT management ,PAVEMENTS ,CONCRETE pavements ,ASPHALT pavements ,INTERNATIONAL airports - Abstract
Airports strive to prevent safety issues, such as foreign object debris (FOD), by pavement management using the pavement condition index (PCI). The index is used in decision-making processes for overall pavement maintenance and repair, such as the prevention of additional damage due to cracks and the like. However, considering the current situation in Korea where mostly mid-sized and large commercial airports exist, problems regarding direct applications of the existing PCI deduct value have been consistently pointed out. In addition, as the relationship between the PCI and whether maintenance and repair are required is unrealistic, there have been difficulties in communication between maintenance and repair staff and decision makers. Therefore, to resolve these problems, this study first analyzed the calculation procedure of the existing PCI and then redefined the main distress type of Korean airport pavements. In addition, a deduct value curve (DVC) in terms of the severity level for six main distress factors of asphalt pavements and eight main distress factors of concrete pavements and a corrected deduct value curve (CDVC) for multiple distresses in terms of the pavement form were developed using panel rating, which is an engineering approach, by forming an airport pavement expert panel. Finally, a Korea airport pavement condition index (KPCI) was proposed using the curves, and the field application results were compared against the existing PCI to examine the adequacy of the KPCI. As a result, the developed criteria showed an overall trend lower than existing PCI. Moreover, it was verified that this trend increases with worsening pavement condition. It appears that a more discriminating evaluation may be possible when determining pavement conditions by PCI results of the developed criteria. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
8. Wavelength-Filter Based Spectral Calibrated Wave number - Linearization in 1.3 mm Spectral Domain Optical Coherence
- Author
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Wijeisnghe, Ruchire Eranga Henry, Cho, Nam Hyun, Park, Kibeom, Shin, Yongseung, and Kim, Jeehyun
- Subjects
Astrophysics::Instrumentation and Methods for Astrophysics ,Article - Abstract
In this study, we demonstrate the enhanced spectral calibration method for 1.3 μm spectral-domain optical coherence tomography (SD-OCT). The calibration method using wavelength-filter simplifies the SD-OCT system, and also the axial resolution and the entire speed of the OCT system can be dramatically improved as well. An externally connected wavelength-filter is utilized to obtain the information of the wavenumber and the pixel position. During the calibration process the wavelength-filter is placed after a broadband source by connecting through an optical circulator. The filtered spectrum with a narrow line width of 0.5 nm is detected by using a line-scan camera. The method does not require a filter or a software recalibration algorithm for imaging as it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. One of the main drawbacks of SD-OCT is the broadened point spread functions (PSFs) with increasing imaging depth can be compensated by increasing the wavenumber-linearization order. The sensitivity of our system was measured at 99.8 dB at an imaging depth of 2.1 mm compared with the uncompensated case.
- Published
- 2013
9. Optical assessment of the in vivo tympanic membrane status using a handheld optical coherence tomography-based otoscope.
- Author
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Park, Kibeom, Cho, Nam Hyun, Jeon, Mansik, Lee, Sang Heun, Jang, Jeong Hun, Boppart, Stephen A., Jung, Woonggyu, and Kim, Jeehyun
- Subjects
- *
TYMPANIC membrane surgery , *DIAGNOSIS , *EAR examination , *ENDOSCOPES , *OTOSCOPES , *STATISTICS , *SURGICAL complications , *TYMPANIC membrane , *DATA analysis , *OPTICAL coherence tomography , *TYMPANIC membrane perforation , *IN vivo studies - Abstract
Objective: Conventional otoscopes and oto-endoscopes, which are used to examine the tympanic membrane (TM), do not provide tomographic information. Optical coherence tomography (OCT) non-invasively reveals the depth-resolved internal microstructure of the TM with very high spatial resolution. We designed this study to examine the TMs with middle ear diseases using a handheld otoscope employing 860nm spectral domain (SD)-OCT, combined with video camera and to demonstrate the clinical applicability of this system. Design: A total of 120 patients with otologic symptoms were enrolled. TM images were obtained using the handheld OCT-based otoscope (860nm central wave length, 15 lm axial resolution, 15 lm lateral resolution, and 7mm scanning range using relay lens). Both OCT and oto-endoscope images were compared according to the clinical characteristics such as perforation, retraction, and postoperative healing process. Results: The objective grade about the thickness of perforation margins and the accurate information about the extent of TM retraction that was not distinguishable by oto-endoscopic exam could be identified using this system. The postoperative healing process of TMs could be also followed using the OCT device. Conclusion: These analyses from the surgeon-oriented perspective suggest another useful application of the handheld OCT device. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
10. Human middle-ear muscle pulls change tympanic-membrane shape and low-frequency middle-ear transmission magnitudes and delays.
- Author
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Cho, Nam Hyun, Ravicz, Michael E., and Puria, Sunil
- Subjects
- *
EAR ossicles , *NECK muscles , *TYMPANIC membrane , *TRANSMISSION of sound , *OPTICAL coherence tomography , *ACOUSTIC localization - Abstract
• Tensor tympani and stapedius muscles were pulled in human cadaver temporal bones. • Muscle pulls reduced low-frequency middle-ear sound transmission and group delay. • Tensor tympani pull changed the tympanic membrane shape and umbo position. • Modulations of middle-ear delay by the muscles could aid sound localization. • Middle-ear muscles could help the brain align head-centered auditory and ocular-centered visual representations of the environment. The three-bone flexible ossicular chain in mammals may allow independent alterations of middle-ear (ME) sound transmission via its two attached muscles, for both acoustic and non-acoustic stimuli. The tensor tympani (TT) muscle, which has its insertion on the malleus neck, is thought to increase tension of the tympanic membrane (TM). The stapedius (St) muscle, which has its insertion on the stapes posterior crus, is known to stiffen the stapes annular ligament. We produced ME changes in human cadaveric temporal bones by statically pulling on the TT and St muscles. The 3D static TM shape and sound-induced umbo motions from 20 Hz to 10 kHz were measured with optical coherence tomography (OCT); stapes motion was measured using laser-Doppler vibrometry (LDV). TT pulls made the TM shape more conical and moved the umbo medially, while St pulls moved the umbo laterally. In response to sound below about 1 kHz, stapes-velocity magnitudes generally decreased by about 10 dB due to TT pulls and 5 dB due to St pulls. In the 250 to 500 Hz region, the group delay calculated from stapes-velocity phase showed a decrease in transmission delay of about 150 µs by TT pulls and 60 µs by St pulls. Our interpretation of these results is that ME-muscle activity may provide a way of mechanically changing interaural time- and level-difference cues. These effects could help the brain align head-centered auditory and ocular-centered visual representations of the environment. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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11. Bio-Photonic Detection and Quantitative Evaluation Method for the Progression of Dental Caries Using Optical Frequency-Domain Imaging Method
- Author
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Wijesinghe, Ruchire Eranga, Cho, Nam Hyun, Park, Kibeom, Jeon, Mansik, and Kim, Jeehyun
- Subjects
optical frequency domain imaging (OFDI) ,optical coherence tomography ,dental caries ,demineralization ,Bio-photonic detection - Abstract
The initial detection of dental caries is an essential biomedical requirement to barricade the progression of caries and tooth demineralization. The objective of this study is to introduce an optical frequency-domain imaging technique based quantitative evaluation method to calculate the volume and thickness of enamel residual, and a quantification method was developed to evaluate the total intensity fluctuation in depth direction owing to carious lesions, which can be favorable to identify the progression of dental caries in advance. The cross-sectional images of the ex vivo tooth samples were acquired using 1.3 μm spectral domain optical coherence tomography system (SD-OCT). Moreover, the advantages of the proposed method over the conventional dental inspection methods were compared to highlight the potential capability of OCT. As a consequence, the threshold parameters obtained through the developed method can be used as an efficient investigating technique for the initial detection of demineralization.
- Published
- 2016
- Full Text
- View/download PDF
12. Non-Destructive Inspection Methods for LEDs Using Real-Time Displaying Optical Coherence Tomography.
- Author
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Cho, Nam Hyun, Jung, Unsang, Kim, Suhwan, and Kim, Jeehyun
- Subjects
- *
LIGHT emitting diodes , *NONDESTRUCTIVE testing , *REAL-time computing , *OPTICAL coherence tomography , *FLUORESCENCE , *CCD cameras , *X-rays , *SPECTRUM analysis - Abstract
In this study, we report the applicability of two different Optical Coherence Tomography (OCT) technologies for inspecting Light Emitting Diode (LED) structures. Sectional images of a LED were captured using a Spectral Domain OCT (SD-OCT) system and a Swept Source OCT (SS-OCT) system. Their center wavelengths are 850 and 1,310 nm, respectively. We acquired cross-sectional two dimensional (2D) images of a normal LED and extracted sectional profiles to inspect possible wire disconnection that may be present in the LED manufacturing process. The SD-OCT and SS-OCT images were compared with each other in the same sample to study their advantages. The distribution of fluorescence material was observed more clearly with the SD-OCT of 850 nm wavelength, whereas the status of wire connection was clearer in the SS-OCT images with 1,310 nm wavelength. In addition, the volume of the fluorophore space was calculated from the OCT images. This is the first report that a nondestructive optical imaging modality such as OCT can be applied to finding screen defects in LED. We expect this method can improve the inspection efficacy over traditional inspection methods such as Charged Coupled Device (CCD) camera or X-ray instruments. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
13. Label‐free optical projection tomography for quantitative three‐dimensional anatomy of mouse embryo.
- Author
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Ban, Sungbea, Cho, Nam Hyun, Min, Eunjung, Bae, Jung Kweon, Ahn, Yujin, Shin, Sungwon, Park, Soo‐Ah, Lee, Yoonsung, and Jung, Woonggyu
- Abstract
Recent progress in three‐dimensional optical imaging techniques allows visualization of many comprehensive biological specimens. Optical clearing methods provide volumetric and quantitative information by overcoming the limited depth of light due to scattering. However, current imaging technologies mostly rely on the synthetic or genetic fluorescent labels, thus limits its application to whole‐body visualization of generic mouse models. Here, we report a label‐free optical projection tomography (LF‐OPT) technique for quantitative whole mouse embryo imaging. LF‐OPT is based on the attenuation contrast of light rather than fluorescence, and it utilizes projection imaging technique similar to computed tomography for visualizing the volumetric structure. We demonstrate this with a collection of mouse embryo morphologies in different stages using LF‐OPT. Additionally, we extract quantitative organ information applicable toward high‐throughput phenotype screening. Our results indicate that LF‐OPT can provide multi‐scale morphological information in various tissues including bone, which can be difficult in conventional optical imaging technique. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
14. Airport concrete pavement design by environmental and double dual tandem gear loadings.
- Author
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Lee, Jun-Hyeok, Kim, Yeon-Tae, Tonn, Sereyvattana, Cho, Nam-Hyun, and Jeong, Jin-Hoon
- Subjects
- *
CONCRETE pavements , *FINITE element method , *AIRPORTS , *REGRESSION analysis , *STATISTICS - Abstract
A method for designing an airport concrete pavement (ACP) that can withstand environmental loads as well as traffic loads is presented. Information on ACPs for which double dual tandem landing gears were used for design aircrafts was collected and the stresses induced on the slabs when environmental loads and traffic loads were simultaneously applied were predicted with the finite-element analysis program FeaFaa. In addition, a maximum tensile stress regression model of ACP slabs was developed using the statistical analysis program SPSS. When environmental and traffic loads were simultaneously applied, the maximum tensile stress obtained with the finite-element method was significantly different from that obtained using Westergaard's equation of edge loading only in traffic loads. Therefore, the fatigue model in the US Federal Aviation Administration's AC 150/5320-6E design method was corrected to be appropriate for this study. Using the stress regression model developed in this study and the corrected fatigue model, the thickness and joint spacing of existing ACP slabs were redesigned and compared with existing airport pavements. Previously, only the thickness of a slab was designed and the joint spacing was empirically determined. However, from the results of this study, a slab's thickness and joint spacing can be designed mechanistically. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
15. Future Directions of Optical Coherence Tomography in Otology: A Morphological and Functional Approach.
- Author
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Cho NH and Jang JH
- Published
- 2020
- Full Text
- View/download PDF
16. In Vivo Vibration Measurement of Middle Ear Structure Using Doppler Optical Coherence Tomography: Preliminary Study.
- Author
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Jeon D, Cho NH, Park K, Kim K, Jeon M, Jang JH, and Kim J
- Abstract
Objectives: Doppler optical coherence tomography (DOCT) is useful for both, the spatially resolved measurement of the tympanic membrane (TM) oscillation and high-resolution imaging. We demonstrated a new technique capable of providing real-time two-dimensional Doppler OCT image of rapidly oscillatory latex mini-drum and in vivo rat TM and ossicles., Methods: Using DOCT system, the oscillation of sample was measured at frequency range of 1-4 kHz at an output of 15 W. After the sensitivity of the DOCT system was verified using a latex mini-drum consisting of a 100 μm-thick latex membrane, changes in displacement of the umbo and contacted area between TM and malleus in normal and pathologic conditions., Results: The oscillation cycles of the mini-drum for stimulus frequencies were 1.006 kHz for 1 kHz, 2.012 kHz for 2kHz, and 3.912 kHz for 4 kHz, which means that the oscillation cycle of the mini-drum become short in proportional to the frequency of stimuli. The oscillation cycles of umbo area and the junction area in normal TM for frequencies of the stimuli showed similar integer ratio with the data of latex mini-drum for stimuli less than 4 kHz. In the case of middle ear effusion condition, the Doppler signal showed a tendency of attenuation in all frequencies, which was prominent at 1 kHz and 2 kHz., Conclusion: The TM vibration under sound stimulation with frequencies from 1 kHz to 4 kHz in normal and pathologic conditions was demonstrated using signal demodulation method in in vivo condition. The OCT technology could be helpful for functional and structural assessment as an optional modality.
- Published
- 2019
- Full Text
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17. In vivo 3D imaging of the human tympanic membrane using a wide-field diagonal-scanning optical coherence tomography probe.
- Author
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Park K, Cho NH, Jang JH, Lee SH, Kim P, Jeon M, Boppart SA, Kim J, and Jung W
- Abstract
A wide-field optical coherence tomography (OCT) probe was developed that adapts a diagonal-scanning scheme for three-dimensional (3D) in vivo imaging of the human tympanic membrane. The probe consists of a relay lens to enhance the lateral scanning range up to 7 mm. Motion artifacts that occur with the use of handheld probes were found to be decreased owing to the diagonal-scanning pattern, which crosses the center of the sample to facilitate entire 3D scans. 3D images could be constructed from a small number of two-dimensional OCT images acquired using the diagonal-scanning technique. To demonstrate the usefulness and performance of the developed system with the handheld probe, in vivo tympanic membranes of humans and animals were imaged in real time.
- Published
- 2017
- Full Text
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18. Optical coherence tomography for the diagnosis and evaluation of human otitis media.
- Author
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Cho NH, Lee SH, Jung W, Jang JH, Boppart SA, and Kim J
- Subjects
- Humans, Reproducibility of Results, Sensitivity and Specificity, Ear, Middle pathology, Otitis Media pathology, Tomography, Optical Coherence methods
- Published
- 2015
- Full Text
- View/download PDF
19. Evaluation of the usefulness of three-dimensional optical coherence tomography in a guinea pig model of endolymphatic hydrops induced by surgical obliteration of the endolymphatic duct.
- Author
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Cho NH, Lee JW, Cho JH, Kim J, Jang JH, and Jung W
- Subjects
- Animals, Calcium Chelating Agents, Cochlea anatomy & histology, Cochlea drug effects, Decalcification Technique, Ear, Inner, Edetic Acid, Endolymphatic Duct surgery, Endolymphatic Hydrops etiology, Evoked Potentials, Auditory, Brain Stem, Guinea Pigs, Image Processing, Computer-Assisted methods, Cochlea diagnostic imaging, Endolymphatic Hydrops diagnostic imaging, Imaging, Three-Dimensional methods, Tomography, Optical Coherence methods
- Abstract
Optical coherence tomography (OCT) has advanced significantly over the past two decades and is currently used extensively to monitor the internal structures of organs, particularly in ophthalmology and dermatology. We used ethylenediamine tetra-acetic acid (EDTA) to decalcify the bony walls of the cochlea and investigated the inner structures by deep penetration of light into the cochlear tissue using OCT on a guinea pig model of endolymphatic hydrops (EH), induced by surgical obliteration of the endolymphatic duct. The structural and functional changes associated with EH were identified using OCT and auditory brainstem response tests, respectively. We also evaluated structural alterations in the cochlea using three-dimensional reconstruction of the OCT images, which clearly showed physical changes in the cochlear structures. Furthermore, we found significant anatomical variations in the EH model and conducted graphical analysis by strial atrophy for comparison. The physical changes included damage to and flattening of the organ of Corti—evidence of Reissner's membrane distention—and thinning of the lateral wall. These results indicate that observation of EDTA-decalcified cochlea using OCT is significant in examination of gradual changes in the cochlear structures that are otherwise not depicted by hematoxylin and eosin staining.
- Published
- 2015
- Full Text
- View/download PDF
20. Lateral resolution enhancement using programmable phase modulator in optical coherence tomography.
- Author
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Shirazi MF, Cho NH, Jung W, and Kim J
- Subjects
- Equipment Design, Equipment Failure Analysis, Phantoms, Imaging, Reproducibility of Results, Sensitivity and Specificity, Image Enhancement instrumentation, Image Interpretation, Computer-Assisted instrumentation, Optical Devices, Signal Processing, Computer-Assisted instrumentation, Tomography, Optical Coherence instrumentation
- Abstract
Adaptive optics plays an important role in the correction of high-order aberrations to enhance lateral resolution. An OCT system coupled with a programmable phase modulator is designed to verify lateral resolution improvement. The Hamamatsu high-resolution, non-pixelized, optically addressed light modulator (PAL-SLM) PPM X7550 series is used to correct aberrations, utilizing a simple method based on phase information from OCT images. The advantages of this method are its high simplicity and low cost. A raster scanning technique is adopted to scan samples covered with scattering suspension. Metal lines covered with scattering suspension are imaged, and a respective correction is applied to remove the aberration. Results demonstrate an improvement in lateral resolution on metal grid samples.
- Published
- 2015
- Full Text
- View/download PDF
21. In vivo imaging of middle-ear and inner-ear microstructures of a mouse guided by SD-OCT combined with a surgical microscope.
- Author
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Cho NH, Jang JH, Jung W, and Kim J
- Subjects
- Animals, Disease Models, Animal, Ear Diseases surgery, Ear, Inner surgery, Ear, Middle surgery, Intraoperative Period, Mice, Diagnostic Imaging, Ear Diseases diagnosis, Ear, Inner pathology, Ear, Middle pathology, Microscopy instrumentation, Otologic Surgical Procedures, Tomography, Optical Coherence instrumentation
- Abstract
We developed an augmented-reality system that combines optical coherence tomography (OCT) with a surgical microscope. By sharing the common optical path in the microscope and OCT, we could simultaneously acquire OCT and microscope views. The system was tested to identify the middle-ear and inner-ear microstructures of a mouse. Considering the probability of clinical application including otorhinolaryngology, diseases such as middle-ear effusion were visualized using in vivo mouse and OCT images simultaneously acquired through the eyepiece of the surgical microscope during surgical manipulation using the proposed system. This system is expected to realize a new practical area of OCT application.
- Published
- 2014
- Full Text
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22. Development of real-time dual-display handheld and bench-top hybrid-mode SD-OCTs.
- Author
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Cho NH, Park K, Wijesinghe RE, Shin YS, Jung W, and Kim J
- Abstract
Development of a dual-display handheld optical coherence tomography (OCT) system for retina and optic-nerve-head diagnosis beyond the volunteer motion constraints is reported. The developed system is portable and easily movable, containing the compact portable OCT system that includes the handheld probe and computer. Eye posterior chambers were diagnosed using the handheld probe, and the probe could be fixed to the bench-top cradle depending on the volunteers' physical condition. The images obtained using this handheld probe were displayed in real time on the computer monitor and on a small secondary built-in monitor; the displayed images were saved using the handheld probe's built-in button. Large-scale signal-processing procedures such as k-domain linearization, fast Fourier transform (FFT), and log-scaling signal processing can be rapidly applied using graphics-processing-unit (GPU) accelerated processing rather than central-processing-unit (CPU) processing. The Labview-based system resolution is 1,024 × 512 pixels, and the frame rate is 56 frames/s, useful for real-time display. The 3D images of the posterior chambers including the retina, optic-nerve head, blood vessels, and optic nerve were composed using real-time displayed images with 500 × 500 × 500 pixel resolution. A handheld and bench-top hybrid mode with a dual-display handheld OCT was developed to overcome the drawbacks of the conventional method.
- Published
- 2014
- Full Text
- View/download PDF
23. Wavelength-Filter Based Spectral Calibrated Wave number - Linearization in 1.3 mm Spectral Domain Optical Coherence.
- Author
-
Wijeisnghe RE, Cho NH, Park K, Shin Y, and Kim J
- Abstract
In this study, we demonstrate the enhanced spectral calibration method for 1.3 μm spectral-domain optical coherence tomography (SD-OCT). The calibration method using wavelength-filter simplifies the SD-OCT system, and also the axial resolution and the entire speed of the OCT system can be dramatically improved as well. An externally connected wavelength-filter is utilized to obtain the information of the wavenumber and the pixel position. During the calibration process the wavelength-filter is placed after a broadband source by connecting through an optical circulator. The filtered spectrum with a narrow line width of 0.5 nm is detected by using a line-scan camera. The method does not require a filter or a software recalibration algorithm for imaging as it simply resamples the OCT signal from the detector array without employing rescaling or interpolation methods. One of the main drawbacks of SD-OCT is the broadened point spread functions (PSFs) with increasing imaging depth can be compensated by increasing the wavenumber-linearization order. The sensitivity of our system was measured at 99.8 dB at an imaging depth of 2.1 mm compared with the uncompensated case.
- Published
- 2013
24. Ultra-fast displaying Spectral Domain Optical Doppler Tomography system using a Graphics Processing Unit.
- Author
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Jeong H, Cho NH, Jung U, Lee C, Kim JY, and Kim J
- Subjects
- Humans, Imaging, Three-Dimensional, Rheology, Signal Processing, Computer-Assisted, Computer Graphics, Doppler Effect, Tomography, Optical methods
- Abstract
We demonstrate an ultrafast displaying Spectral Domain Optical Doppler Tomography system using Graphics Processing Unit (GPU) computing. The calculation of FFT and the Doppler frequency shift is accelerated by the GPU. Our system can display processed OCT and ODT images simultaneously in real time at 120 fps for 1,024 pixels × 512 lateral A-scans. The computing time for the Doppler information was dependent on the size of the moving average window, but with a window size of 32 pixels the ODT computation time is only 8.3 ms, which is comparable to the data acquisition time. Also the phase noise decreases significantly with the window size. Since the performance of a real-time display for OCT/ODT is very important for clinical applications that need immediate diagnosis for screening or biopsy. Intraoperative surgery can take much benefit from the real-time display flow rate information from the technology. Moreover, the GPU is an attractive tool for clinical and commercial systems for functional OCT features as well.
- Published
- 2012
- Full Text
- View/download PDF
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