• 대한디지털의료영상학회논문지
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• 제5권1호
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• pp.46-63
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• 2002

This thesis describes the effective interfacing methods of PACS Modality based on the system installation and operating experiences. PACS(Picture Archiving and Communication Systems) is a system for medical image archiving and communication using large storage device and high-speed network. The standard communication protocol of PACS is DICOM(Digital Imaging and Communication in Medicine) based on TCP/IP and point-to-point protocol. However, there are many Non-DICOM Modalities and DICOM Modalities having problems. First, we had interfaced almost modalities, Fuji CR, GE CT, MRI, Angio, Fluoro, Phillips Angio, Shimadzu Fluoro, Ultrasound PACS, with the main PACS in the Seoul S Hospital as large scale hospital. And we manipulated the intelligent image distribution and the CT, MRI Interfaces never experienced before in the Anyang J Hospital and the Chungju C Hospital as mid or small scale hospital. Technically, we developed both the DICOM Interface and the Non-DICOM Interface. At the last, the DICOM Worklist and the DICOM Print Interface were implemented in the Seoul B Hospital, the Bucheon SJ Hospital and the Seoul K Hospital independently with PACS. The Oracle, Sybase and MS-SQL are used as database, and UNIX, Macintosh, MS Windows as operating systems. And the Visual C++ and UNIX C are the main programming tools. We have used UTP, coaxial and fiber optic Gable under 10/100 mbps LAN for networking.

• 천문학회보
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• 제38권1호
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• pp.63.2-63.2
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• 2013

We have investigated the EUV coronal jets observed by Solar Dynamic Observatory (SDO) / Atmospheric Imaging Assembly (AIA). From the Heliophysics Events Knowledgebase (HEK), we consider all recorded 40 EUV jets in $171{\AA}$ from May 2010 to July 2011 and use 19 jets whose location can be clearly identified, excluding limb events because of the ambiguity of their positions. According to the positions of their roots, these coronal jets are classified into two types: bright point jet (BPJ, 9 jets) and active region boundary jet (ABJ, 10 jets). BPJs are located at the top of bright points and ABJs at the boundaries of active regions. There are significant differences in speed and size between two types. Here the speed and size of a jet are assumed to be its maximum values in the case that the jet has several ejections. The average speed and size of 9 BPJs are about 110 km/s and 69,000km, respectively. The average speed and size of 10 ABJs are about 660 km/s and 194,000 km, respectively. The speed distribution of ABJs has two peaks at about 270 km/s and 1700 km/s. It is very interesting to note that three ABJs have very high speeds larger than 1600 km/s and they are all composed of a group of recurrent jets with low and high speed at the same location. In addition, we are investigating these events in other wavelengths and compare their characteristics.

• Applied Microscopy
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• 제50권
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• pp.25.1-25.11
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• 2020

Scanning acoustic microscopy (SAM) or Acoustic Micro Imaging (AMI) is a powerful, non-destructive technique that can detect hidden defects in elastic and biological samples as well as non-transparent hard materials. By monitoring the internal features of a sample in three-dimensional integration, this technique can efficiently find physical defects such as cracks, voids, and delamination with high sensitivity. In recent years, advanced techniques such as ultrasound impedance microscopy, ultrasound speed microscopy, and scanning acoustic gigahertz microscopy have been developed for applications in industries and in the medical field to provide additional information on the internal stress, viscoelastic, and anisotropic, or nonlinear properties. X-ray, magnetic resonance, and infrared techniques are the other competitive and widely used methods. However, they have their own advantages and limitations owing to their inherent properties such as different light sources and sensors. This paper provides an overview of the principle of SAM and presents a few results to demonstrate the applications of modern acoustic imaging technology. A variety of inspection modes, such as vertical, horizontal, and diagonal cross-sections have been presented by employing the focus pathway and image reconstruction algorithm. Images have been reconstructed from the reflected echoes resulting from the change in the acoustic impedance at the interface of the material layers or defects. The results described in this paper indicate that the novel acoustic technology can expand the scope of SAM as a versatile diagnostic tool requiring less time and having a high efficiency.

• 한국가시화정보학회지
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• 제19권3호
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• pp.15-21
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• 2021

In this study, we investigated the dynamics of a droplet impacting rough hydrophobic surfaces through high-speed imaging. Micrometer-sized structures with grooves and pillars were fabricated on smooth Polydimethylsiloxane (PDMS) surfaces by laser ablation. We used Newtonian and non-Newtonian liquid droplets to study the drop impact dynamics. De-ionized water and aqueous glycerin solutions were used for the Newtonian liquid droplet. The solutions of xanthan gum in water were prepared to provide elastic property to the Newtonian droplet. We found that the orientation of the surface structures affected the maximal spreading diameter of the droplet due to the degree of slippage. During the droplet retraction, the dynamic receding contact angles were measured to be around 90° or less. It resulted in the formation of the micro-capillary bridges between the receding droplet and the surface structures. Then, the rupture of the capillary bridge led to the formation of micrometer-sized droplets on top of the surface structures. The size of the microdroplets was found to increase with increasing the impacting velocity and viscosity of the Newtonian liquid droplets. However, the size of the isolated microdroplets decreased with enhancing the elasticity of the droplets, and the size of the non-Newtonian microdroplets was not affected by the impacting velocity.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.763-764
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• 2013

A three-dimensional image capturing device and its signal processing algorithm and apparatus are presented. Three dimensional information is one of emerging differentiators that provides consumers with more realistic and immersive experiences in user interface, game, 3D-virtual reality, and 3D display. It has the depth information of a scene together with conventional color image so that full-information of real life that human eyes experience can be captured, recorded and reproduced. 20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system prototype are presented[1,2]. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of 20MHz high-speed micro-optical image modulator, so called 'optical resonator'. The high speed image modulation is obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical resonance cavity which maximizes the magnitude of optical modulation[3,4]. The optical resonator is specially designed and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the object to capture a depth image (Figure 1). Suggested novel optical resonator enables capturing of a full HD depth image with depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture 14Mp color and full HD depth images, simultaneously (Figure 2,3). The resulting high definition color/depth image and its capturing device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical resonator design, fabrication, 3D camera system prototype and signal processing algorithms.

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.27-32
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• 2008

This paper describes a contact atomic force microscope (AFM) that can be used for high-speed precision measurements of microstructured surfaces. The AFM is composed of an air-bearing X stage, an air-bearing spindle with the axis of rotation in the Z direction, and an AFM probe unit. The traversing distance and maximum speed of the X stage are 300 mm and 400 mm/s, respectively. The spindle has the ability to hold a sample in a vacuum chuck with a maximum diameter of 130 mm and has a maximum rotation speed of 300 rpm. The bandwidth of the AFM probe unit in an open loop control circuit is more than 40 kHz. To achieve precision measurements of microstructured surfaces with slopes, a scanning strategy combining constant height measurements with a slope compensation technique is proposed. In this scanning strategy, the Z direction PZT actuator of the AFM probe unit is employed to compensate for the slope of the sample surface while the microstructures are scanned by the AFM probe at a constant height. The precision of such a scanning strategy is demonstrated by obtaining profile measurements of a microstructure surface at a series of scanning speeds ranging from 0.1 to 20.0 mm/s.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.220-220
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• 2013

Surface-normal transmission electro-absorption modulator (EAM) are attractive for high-definition (HD) three-dimensional (3D) imaging application due to its features such as small system volume and simple epitaxial structure [1,2]. However, EAM in order to be used for HD 3D imaging system requires uniform modulation performance over large area. To achieve highly uniform modulation performance of EAM at the operating wavelength of 850 nm, it is extremely important to remove the GaAs substrate over large area since GaAs material has high absorption coefficient below 870 nm which corresponds to band-edge energy of GaAs (1.424 eV). In this study, we propose and experimentally demonstrate a transmission EAM in which highly selective backside etching methods which include lapping, dry etching and wet etching is carried out to remove the GaAs substrate for achieving highly uniform modulation performance. First, lapping process on GaAs substrate was carried out for different lapping speeds (5 rpm, 7 rpm, 10 rpm) and the thickness was measured over different areas of surface. For a lapping speed of 5 rpm, a highly uniform surface over a large area ($2{\times}1\;mm^2$) was obtained. Second, optimization of inductive coupled plasma-reactive ion etching (ICP-RIE) was carried out to achieve anisotropy and high etch rate. The dry etching carried out using a gas mixture of SiCl4 and Ar, each having a flow rate of 10 sccm and 40 sccm, respectively with an RF power of 50 W, ICP power of 400 W and chamber pressure of 2 mTorr was the optimum etching condition. Last, the rest of GaAs substrate was successfully removed by highly selective backside wet etching with pH adjusted solution of citric acid and hydrogen peroxide. Citric acid/hydrogen peroxide etching solution having a volume ratio of 5:1 was the best etching condition which provides not only high selectivity of 235:1 between GaAs and AlAs but also good etching profile [3]. The fabricated transmission EAM array have an amplitude modulation of more than 50% at the bias voltage of -9 V and maintains high uniformity of >90% over large area ($2{\times}1\;mm^2$). These results show that the fabricated transmission EAM with substrate removed is an excellent candidate to be used as an optical shutter for HD 3D imaging application.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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• pp.69-72
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• 2000

This paper shows the more improved design of MRI receiver compared to conventional one based on Elscint Spectrometer. At first, the low-cost ADC is 16 bits, 3MHz sampling A/D converter Comparing to conventional one with signal bits of 14 bits, this device with those of 16 bits helps getting Improved the image resolution improved. If frequency is designed centering around 7.6 MHz to be satisfied in 10 MHz of maximum input bandwidth of ADC. For 1st demodulation, fixed IF is used for the purpose of the implementing multi nuclei system. Control parts & partial digital parts are integrated on one chip(FPGA). In DDC(Digital Down Converter), we got required bandwidth of LPF by controlling its decimation rate. With above considerations, we designed optimal receiver for high resolution imaging to be implemented through PC interface & experimental test of receiver of MRI after receiver's fabrication.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.569-574
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• 1998

This paper presents a two-paralleled 4 quadrant DC chopper type PWM power conversion circuit in order to generate a gradient magnetic field in the Magnetic Resonance Imaging (MRI) system. This power amplifier is connected in parallel with the conventional 4-quadrant DC chopper using IGBTs at their inputs/outputs to realize further high-power density, high speed current tracking control, and to get a low switching ripple amplitude in a controlled current in the Gradient Coils (GCs). Moreover, the power conversion circuit has to realize quick rise/fall response characteristics in proportion to various target currents in GCs. It is proposed in this paper that a unique control scheme can achieve the above objective. DSP-based control systems realize a high control facility and accuracy. It is proved that the new control system will greatly enlarge the diagnostic target and improve the image quality of MRI.

• Journal of Korean Neurosurgical Society
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• 제60권5호
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• pp.485-497
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• 2017

Surgical treatment of the degenerative disc disease has evolved from traditional open spine surgery to minimally invasive spine surgery including endoscopic spine surgery. Constant improvement in the imaging modality especially with introduction of the magnetic resonance imaging, it is possible to identify culprit degenerated disc segment and again with the discography it is possible to diagnose the pain generator and pathological degenerated disc very precisely and its treatment with minimally invasive approach. With improvements in the optics, high resolution camera, light source, high speed burr, irrigation pump etc, minimally invasive spine surgeries can be performed with various endoscopic techniques for lumbar, cervical and thoracic regions. Advantages of endoscopic spine surgeries are less tissue dissection and muscle trauma, reduced blood loss, less damage to the epidural blood supply and consequent epidural fibrosis and scarring, reduced hospital stay, early functional recovery and improvement in the quality of life & better cosmesis. With precise indication, proper diagnosis and good training, the endoscopic spine surgery can give equally good result as open spine surgery. Initially, endoscopic technique was restricted to the lumbar region but now it also can be used for cervical and thoracic disc herniations. Previously endoscopy was used for disc herniations which were contained without migration but now days it is used for highly up and down migrated disc herniations as well. Use of endoscopic technique in lumbar region was restricted to disc herniations but gradually it is also used for spinal canal stenosis and endoscopic assisted fusion surgeries. Endoscopic spine surgery can play important role in the treatment of adolescent disc herniations especially for the persons who engage in the competitive sports and the athletes where less tissue trauma, cosmesis and early functional recovery is desirable. From simple chemonucleolysis to current day endoscopic procedures the history of minimally invasive spine surgery is interesting. Appropriate indications, clear imaging prior to surgery and preplanning are keys to successful outcome. In this article basic procedures of percutaneous endoscopic lumbar discectomy through transforaminal and interlaminar routes, percutaneous endoscopic cervical discectomy, percutaneous endoscopic posterior cervical foraminotomy and percutaneous endoscopic thoracic discectomy are discussed.