• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.1-13
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• 2010

This paper describes a development of a fiber optic common-path optical coherence tomography (OCT) based imaging and guided system that possess ability to reliably identify optically transparent targets that are on the micron scale; ability to maintain a precise and safe position from the target; ability to provide spectroscopic imaging; ability to imaging biological target in 3-D. The system is based on a high resolution fiber optic Common-Path OCT (CP-OCT) that can be integrated into various mini-probes and tools. The system is capable of obtaining >70K A-scan per second with a resolution better than $3\;{\mu}m$. We have demonstrated that the system is capable of one-dimensional real-time depth tracking, tool motion limiting and motion compensation, oxygen-saturation level imaging, and high resolution 3-D images for various biomedical applications.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.192-193
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• 2020

In reinforced concrete adhesion studies, the demolition of the specimen is inevitably involved, and the studies conducted are limited to the macro load-displacement analysis. In order to establish an elaborate model for concrete bonding reinforced rebars, it is necessary to observe the rebar bonding behavior in the in-situ state. In this study, specially manufactured reinforcing bars, micro-UTM and 𝝁-computer tomography (𝝁CT) are used to observe reinforcing bars in the in-situ state. As a result of the monotonic pullout test of the processed reinforcing bar, maximum bond stress were shown to be 16.7MPa, which is slightly higher than the existing 10 to 12 MPa, and then the empty space inside the specimen in which the pullout test was conducted using 𝝁CT was confirmed. Through additional research, the fracture phenomenon of concrete excluding voids will be studied.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.74-77
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• 2011

We report a novel extension of 840 nm wavelength- based spectral domain optical tomography to in vivo/real-time human middle ear diagnosis. The system was designed to access the middle ear region with a specifically dedicated handheld probe. The real-time displaying feature was mandatory for in vivo imaging human subject with the handheld probe, and the system could provide about 20 frames per second for 2048 pixels by 1000 A-scans without using any graphics process units under the Labview platform. The inner ear structure of a healthy male volunteer was imaged with the developed system with the axial and lateral resolutions of $15\;{\mu}m$ and $30\;{\mu}m$, respectively. The application of the OCT technology to early diagnose otitis media(OM) is very promising and could be another extensive branch in the OCT field because it provides the depth resolved image including tympanic membrane (TM) and structures below TM whereas the conventional otoscope technique only gives asurface image of the TM.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.252-253
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• 2019

Corrosion of rebars in reinforced concrete structures is a major factor that shortens the life of the structure. As corrosion progresses, the adhesion between the concrete tissues and the rebar decreases and the cracks in the concrete due to the expansion of the oxide intensify. Although it is necessary to measure corrosion behavior of rebars inside the concrete to measure degradation of structures due to rebar corrosion, no studies have been conducted to measure corrosion of rebars in In-situ state. In this study, corrosion of rebars in reinforced concrete specimens was attempted to be quantified using micro-computer tomography. Since corrosion of concrete takes several months per 10mm of cover, accelerated corrosion techniques were applied. Accelerated corrosion on the specimen was conducted by applying a 10 V magnetic field to the buried rebar and external electrodes with the specimen submerged in a 10% calcium chloride solution. The experiment found that within two weeks, more than 40% of rebar reduction occurred, and the cracks in the radial cracks occurred through the concrete structure, leading to the transfer of the oxide produced through the cracks to the surface of the specimen.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.459-464
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• 2019

In order to minimize the radiation exposure dose of the thyroid site at dental cone-beam computer tomography, a protector using a Bolus was prepared, and the radiation shielding effect and the appropriateness of the image were evaluated. Using a dental cone-beam computed tomography (CBCT), a glass dosimeter was attached to the left and right sides of the thyroid for a dental radiation phantom, and the radiation dose was measured. The absorbed dose for each shield was measured by another method to 10 mm, 20 mm, and 30 mm-thickness, respectively. Eight evaluators evaluated whether or not the medical image is appropriate. When using a 30 mm Bolus shield at the left thyroid site, the resulting value is reduced by an average of $342.67{\mu}Gy$ by 20.7% from the average value of $431.22{\mu}Gy$ measured without using a Bolus shield, the right thyroid site In the case of using 30 mm Bolus shield, it showed a dose reduction effect of 21.9% with an average of $424.56{\mu}Gy$. The adequacy of the medical image was judged to be usable by both evaluators. In conclusion, the dental cone-beam computerized tomography can be used as a useful shielding material because it has a radiation shielding effect and it is possible to treat the diagnosis of the bolus protector in the thyroid without any obstruction shade in order to minimize the radiation dose.

• Journal of Sensor Science and Technology
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• v.21 no.3
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• pp.217-222
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• 2012

Optical coherence tomography(OCT) is a noninvasive optical imaging tool for biomedical applications. OCT can provide depth resolved two/three dimensional morphological images on biological samples. In this paper, we integrated an OCT system that was composed of an SLED(Superluminescent Light Emitting Diode, ${\lambda}_0$=1305 nm bandwith= 141 nm), a reference arm adopting a rapid scanning optical delay line(RSOD) to get high speed imaging, and a sample arm that used a micro electro mechanical systems(MEMS) scanning mirror. The sample arm contained a compact probe for imaging dental structures. The performance of the system was evaluated by imaging in-vivo human teeth with dental calculus, and the results indicated distinct appearance of dental calculus from enamel, gum or decayed teeth. The developed probe and system could successfully confirm the presence of dental calculus with a very high spatial resolution($6{\mu}m$).

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.3
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• pp.181-190
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• 1998

A computerized tomography system was developed using the X-ray source that has diameter of 5 micrometer. The system is used for the nondestructive testing of specimens with diameter below 20 mm. The convolution back projection algorithm was adopted for the reconstruction of cross sectional image, and the shape of the X-ray beam was let parallel beam or fan beam to compare each resultant image. Our CT system was constructed to operate based on the personal computer. The sectional images of the fabricated specimens were reconstructed and analyzed. The reconstructed images well coincided with real images taken with optical microscope and gave us enough reports on the defects in the ceramic specimen. The resolution of the system regarded as about $20{\sim}30$ micrometers.

• Imaging Science in Dentistry
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• v.48 no.1
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• pp.21-30
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• 2018

Purpose: To calculate the effective doses of cone-beam computed tomography (CBCT) using personal computer-based Monte Carlo (PCXMC) software (Radiation and Nuclear Safety Authority, Helsinki, Finland) and to compare the calculated effective doses with those measured using thermoluminescent dosimeters (TLDs) and an anthropomorphic phantom. Materials and Methods: An Alphard VEGA CBCT scanner (Asahi Roentgen Ind. Co., Kyoto, Japan) with multiple fields of view (FOVs) was used for this study. The effective doses of the scout and main projections of CBCT using 1 large and 2 medium FOVs with a height >10 cm were calculated using PCXMC and PCXMCRotation software and then were compared with the doses obtained using TLD-100 LiF and an anthropomorphic adult human male phantom. Furthermore, it was described how to determine the reference points on the Y- and Z-axes in PCXMC, the important dose-determining factors in this software. Results: The effective doses at CBCT for 1 large ($20.0cm{\times}17.9cm$) and 2 medium FOVs ($15.4cm{\times}15.4cm$ and $10.2cm{\times}10.2cm$) calculated by the PCXMC software were 181, 300, and $158{\mu}Sv$, respectively. These values were comparable (16%-18% smaller) to those obtained through TLD measurements in each mode. Conclusion: The use of PCXMC software could be an alternative to the TLD measurement method for effective dose estimation in CBCT with large and medium FOVs.

• Journal of radiological science and technology
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• v.39 no.1
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• pp.35-42
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• 2016

Room-temperature operating CdZnTe(CZT) material is an innovative radiation detector which could reduce the patient dose to one-tenth level of conventional CT (Computed Tomography) and mammography system. The pixel and pixel pitch in the imaging device determine the conversion efficiency of incident X-or gamma-ray and the cross-talk of signal, that is, image quality of detector system. The weighting potential is the virtual potential determined by the position and geometry of electrode. The weighting potential obtained by computer-based simulation in solving Poisson equation with proper boundaries condition. The pixel was optimized by considering the CIE (charge induced efficiency) and the signal cross-talk in CT detector system. The pixel pitch was 1-mm and the detector thickness was 2-mm in the simulation. The optimized pixel size and inter-pixel distance for maximizing the CIE and minimizing the signal cross-talk is about $750{\mu}m$ and $125{\mu}m$, respectively.

• Journal of Periodontal and Implant Science
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• v.47 no.1
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• pp.41-50
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• 2017

Purpose: The aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging. Methods: We evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically. Results: The detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than $100{\mu}m$. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform. Conclusions: We were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.