• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.913-915
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• 1996

This paper proposes the proper phase arrangement of transmission lines for reducing the zero sequence circulating current. It is a well-known fact that the zero sequence circulating currents are principally caused by the untranposed lines and numerical estimation method already has been established. In this paper, the circuit analysis for calculating the zero sequence circulating currents was performed on the existing 154kV four-circuit systems of KEPCO and the proper phase arrangement was determined.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.116-123
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• 2004

An experimental investigation was performed to study the characteristics of ER (Electro-Rheological) fluid flow in a horizontal rectangular tube with or without D.C volatage. To determine some characteristics of the ER flow. 2D PIV(Particle Image Velocimetry) technique is employed for velocity measurement. This research found the mean velocity distribution with 0 kV/mm. 1.0kV/mm and 1 5kV/mm for Re=0, 0.62, 1.29 and 2.26. When the strength of the electric field increased. the claster of ERF are clearly strong along the test tube and the flow rate decreased.

• The Journal of the Korea Contents Association
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• v.14 no.8
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• pp.233-242
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• 2014

The purpose of this study is to compare the reduction of the dose radioactivity by CARE kV with that of the Bismuth shielding. First, CT was performed with transparent materials, including a Bismuth shielder which is a well-known material for decreasing the dose of radiation. Moreover, we have estimated and compared the affects of the reduction of dose on eye lens, thyroid, breast and genitals. These steps aim to compare reactions with and without the application of the Rando phantom with PLD as well as with CARE kV or not. As a result, during the Brain angio scan, the dose of CARE kV set inspection test methods showed the least dose. Depending on whether we use CARE kV, which showed the effect of dose reduction by 63%. During the Carotid angio scan, the dose was increased by 13% by how to set CARE kV+Bismuth. During the Cardiac angio scan, which showed the effect of dose reduction by 31% by how to set CARE kV+Bismuth. During the Lower extremity angio scan, the dose was measured least by how to set up the whole Bismuth. Compared with CARE kV set of test methods, which showed the effect of dose reduction by 9%.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.157-165
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• 2012

Purpose: We evaluated usefulness of abdominal compressor for stereotactic body radiotherapy (SBRT) with unresectable hepatocellular carcinoma (HCC) patients and hepato-biliary cancer and metastatic liver cancer patients. Materials and Methods: From November 2011 to March 2012, we selected HCC patients who gained reduction of diaphragm movement >1 cm through abdominal compressor (diaphragm control, elekta, sweden) for HT (Hi-Art Tomotherapy, USA). We got planning computed tomography (CT) images and 4 dimensional (4D) images through 4D CT (somatom sensation, siemens, germany). The gross tumor volume (GTV) included a gross tumor and margins considering tumor movement. The planning target volume (PTV) included a 5 to 7 mm safety margin around GTV. We classified patients into two groups according to distance between tumor and organs at risk (OAR, stomach, duodenum, bowel). Patients with the distance more than 1 cm are classified as the 1st group and they received SBRT of 4 or 5 fractions. Patients with the distance less than 1 cm are classified as the 2nd group and they received tomotherapy of 20 fractions. Megavoltage computed tomography (MVCT) were performed 4 or 10 fractions. When we verify a MVCT fusion considering priority to liver than bone-technique. We sent MVCT images to Mim_vista (Mimsoftware, ver .5.4. USA) and we re-delineated stomach, duodenum and bowel to bowel_organ and delineated liver. First, we analyzed MVCT images to check the setup variation. Second we compared dose difference between tumor and OAR based on adaptive dose through adaptive planning station and Mim_vista. Results: Average setup variation from MVCT was $-0.66{\pm}1.53$ mm (left-right) $0.39{\pm}4.17$ mm (superior-inferior), $0.71{\pm}1.74$ mm (anterior-posterior), $-0.18{\pm}0.30$ degrees (roll). 1st group ($d{\geq}1$) and 2nd group (d<1) were similar to setup variation. 1st group ($d{\geq}1$) of $V_{diff3%}$ (volume of 3% difference of dose) of GTV through adaptive planing station was $0.78{\pm}0.05%$, PTV was $9.97{\pm}3.62%$, $V_{diff5%}$ was GTV 0.0%, PTV was $2.9{\pm}0.95%$, maximum dose difference rate of bowel_organ was $-6.85{\pm}1.11%$. 2nd Group (d<1) GTV of $V_{diff3%}$ was $1.62{\pm}0.55%$, PTV was $8.61{\pm}2.01%$, $V_{diff5%}$ of GTV was 0.0%, PTV was $5.33{\pm}2.32%$, maximum dose difference rate of bowel_organ was $28.33{\pm}24.41%$. Conclusion: Despite we saw diaphragm movement more than 5 mm with flouroscopy after use an abdominal compressor, average setup_variation from MVCT was less than 5 mm. Therefore, we could estimate the range of setup_error within a 5 mm. Target's dose difference rate of 1st group ($d{\geq}1$) and 2nd group (d<1) were similar, while 1st group ($d{\geq}1$) and 2nd group (d<1)'s bowel_organ's maximum dose difference rate's maximum difference was more than 35%, 1st group ($d{\geq}1$)'s bowel_organ's maximum dose difference rate was smaller than 2nd group (d<1). When applicating SBRT to HCC, abdominal compressor is useful to control diaphragm movement in selected patients with more than 1 cm bowel_organ distance.

• The korean journal of orthodontics
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• v.35 no.5 s.112
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• pp.388-397
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• 2005

The purpose of this study was to redefine the cephalometric landmarks in three-dimensional (3D) images, which are used in orthodontic cephalometric radiography, and to evaluate the reproducibility of each landmark for 3D cephalometric analysis. Eighteen CT scans were taken at the Department of Diagnostic Radiology at Seoul National University Dental Hospital and manipulated with V works 4.0(Cybermed Inc., Seoul, Korea). The coordinate system was established using 7 reference points, with no more than 4 points on the same plane. These 7 points were generated as a volume model, the voxel size of which was 4 by 4 by 2 (threshold value=639). The cephalometric landmarks were selected at the multiplanar reformation (MPR) window on the volume mode of V works 4.0. The selected landmarks were exported to V surgery (Cybermed Inc., Seoul, Korea) for the calculation of coordinate values. All the data were taken twice with a lapse of 2 weeks by one investigator The reproducibility of each landmark was $0.17\~1.21mm$ in the x axis, $0.30\~1.53mm$. In the y axis, and $0.27\~1.81mm$ in the z axis. In all three axes, the range of error was similar. These error ranges were acceptable with regards to the pixel space and slice thickness. The most reproducible points were 1 points which were selected on the basis of the volume model. The least reproducible points were J points that were defined by sutures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.6
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• pp.1046-1055
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• 1994

In this paper, to design high speed 1 line VRAM(Video RAM) suitable for image signal processing with ASIC(Application Specific IC) method, the VRAM memory core has been designed using 3-TR dual-port dynamic cell which has excellent access time and integration characteristics. High speed pipeline operation was attained by separating the first row from the subarray 1 memory core and the simultaneous I/Q operation for a selected single address was made possible by adopting data-latch scheme. Peripheral circuits were designed implementing address selector and 1/2V voltage generator. Integrated ASIC has been optimized using 1.5[ m] CMOS design rule.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.131-136
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• 2013

Purpose: Quantitative comparative evaluation of the difference in eye lens absorbed dose when measured by MVCT and kV-CBCT, though such a dose was not included in the original IMRT treatment plan for the nasopharyngeal cancer patient. Materials and Methods: We used CT (Lightspeed Ultra 16, General Electric, USA) against an Anderson rando phantom (Alderson Research Laboratories Inc, USA) and established the plan for tomotherapy treatment (Tomotherapy, Inc, USA) and linear accelerator treatment (Pinnacle 8.0, Philips Medicle System) for the achieved CT images on the same condition with the nasopharyngeal cancer patient treatment plan. Then, align the ther-moluminescence dosimeter (TLD100 Harshaw, USA) with the eye lens, shot the lens with Tomotherapy MVCT under 3 conditions (Fine, Normal, and Coarse), and shot both lenses with kV-CBCT under 2 conditions (Low Dose Head and Standard Dose Head) 3 times each. Results: When we analyzed the eye lens absorbed dose according to MVCT and kV-CBCT images by using both Tomotherapy and Pinacle 8.0, we achieved the following result; According to Tomotherapy MVCT, RT 0.8257 cGy in the Coarse mode, LT 0.8137 cGy, RT 1.089 cGy and LT 1.188 cGy in the Normal mode, and RT 2.154 cGy and LT 2.082 cGy in the Fine mode. According to Pinacle 8.0 kV-CBCT, RT 0.2875 cGy and LT 0.1676 cGy in the Standard Dose mode and RT 0.1648 cGy and LT 0.1212 cGy in the Low-Dose mode. In short, the MVCT result was significantly different from that of kV-CBCT, up to 20 times. Conclusion: We think kV-CBCT is more effective for reducing the amount of radiation which a patient is receiving during intensity modulated radiation treatment for other purposes than treatment than MVCT, when we consider the absorbed dose only from the viewpoint of image-guided radiation therapy. Besides, we understood the amount of radiation is too sensitive to the shooting condition, even when we use the same equipment.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.8
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• pp.47-54
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• 1998

With the increasing popularity of the use of large-volume image database in various application, it becomes imperative to build an efficient and fast retrieval system to browse through the entire database. We present a new method for a content-based image retrieval by using a variable block size and block matching algorithm. Proposed approach is reflecting image features that exploit visual cues such as color and space allocation of image and is getting the fast retrieval time by automatical convergence of retrieval times which adapt to wanting similarity value. We have implemented this technique and tested it for a database of approximately 150 images. The test shows that a 1.9 times fast retrieval time compare to J & V algorithm at the image retrieval efficiency 0.65 and that a 1.83 times fast retrieval time compare to predefined fixed block size.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.53-58
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• 2013

Purpose: To optimize correction method for SPECT/CT, image quality consisting of resolution and contrast was evaluated using three radioisotopes ($^{99m}Tc$, $^{201}Tl$ and $^{131}I$) and three different correction methods; attenuation correction (AC), scatter correction (SC) and both attenuation and scatter correction (ACSC). Materials and Methods: Images were acquired with a SPECT/CT scanner and a conventional CT protocol with an OESM reconstruction algorithm (2 iterations and 10 subsets). For resolution measurement, fixed radioactivity (2.22 kBq) was infused into a spatial resolution phantom and full width at half maximum (FWHM) was measured using a vendor-provided software. For contrast evaluation, radioactive source with a ratio of 1:8 to background was filled in a Flanged Jaszczak phantom and percent contrast (%) were calculated. All the parameters for image quality were compared with non-correction (NC) method. Results: As compared with NC, image resolution of all three isotopes were significantly improved by AC and ACSC, not by SC. In particular, ACSC showed better resolution than AC alone for $^{99m}Tc$ and $^{201}Tl$. Image contrast of all three radioisotopes in a sphere with the largest diameter were enhanced by all correction methods. ACSC showed the highest contrast in all three radioisotopes, which was the most accurate in $^{99m}Tc$ (85.9%). Conclusion: Image quality of SPECT/CT was improved in all the radioisotopes by CT-based attenuation correction methods, except SC alone. SC failed to improve resolution in any radioisotopes, but it was effective in contrast enhancement. ACSC would be the best correction method as it improved resolution in radioisotopes with low energy levels and contrast in radioisotope with low energy levels. However, in radioisotope with high energy level, AC would be better than ACSC for resolution improvement.

• Radiation Oncology Journal
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• v.29 no.2
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• pp.107-114
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• 2011

Purpose: To assess the degree and clinical impact of location error of the dens on the X-axis during radiotherapy to brain and head and neck tumors. Materials and Methods: Twenty-one patients with brain tumors or head and neck tumors who received three-dimensional conformal radiation therapy or intensity-modulated radiation therapy from January 2009 to June 2010 were included in this study. In comparison two-dimensional verification portal images with initial simulation images, location error of the nasal septum and the dens on the X-axis was measured. The effect of set-up errors of the dens was simulated in the planning system and analyzed with physical dose parameters. Results: A total of 402 portal images were reviewed. The mean location error at the nasal septum was 0.16 mm and at the dens was 0.33 mm (absolute value). Location errors of more than 3 mm were recorded in 43 cases (10.7%) at the nasal septum, compared to 133 cases (33.1%) at the dens. There was no case with a location error more than 5 mm at the nasal septum, compared to 11 cases (2.7%) at the dens. In a dosimetric simulation, a location error more than 5 mm at the dens could induce a reduction in the clinical target volume 1 coverage (V95: 100%${\rightarrow}$87.2%) and overdosing to a critical normal organ (Spinal cord V45: <0.1%${\rightarrow}$12.6%). Conclusion: In both brain and head and neck radiotherapy, a relatively larger set-up error was detected at the dens than the nasal septum when using an electronic portal imaging device. Consideration of the location error of the dens is necessary at the time of the precise radiation beam delivery in two-dimensional verification systems.