• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.43-49
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• 2007

Purpose: The aim of this study was the clinical implementation of IGRT using KV CBCT for setup correction in radiation therapy. Materials and Methods: We selected 9 patients (3 patient for each region; head, body, pelvis)and acquired 135 CBCT images with CLINAC iX (Varian medical system, USA). During the scan, the required time was measured. We analyzed the result in 3 direction; vertical, longitudinal, lateral. Results: The mean setup errors at the couch position of vertical, lateral, and longitudinal direction were 0.07, 0.12, and 0.1 cm in the head region, 0.3, 0.26, and 0.22 cm in the body region, 0.21, 0.18, and 0.15 cm in the pelvis region respectively. The mean time required for CBCT was $6{\sim}7$ minute. Conclusion: The CBCT on the LINAC provides the capacity for soft tissue imaging in the treatment position and real time monitoring during treatment delivery. With presented workflow, the setup correction within reasonable time for more accurate radiation therapy is possible. And it's image can be very useful for adaptive radiation therapy(ART) in the future with improved image quality.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.55-62
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• 2007

Purpose: Digital medical image commenced with an introduction of PACS has become more popular today in the radiation diagnosis and medical treatment and made great progress, in particular, for medical testing field, whereas it has made slow progress for radiation therapy area. In order to accommodate the current trend of digital from analog, a spherical type mechanical check device (SMCD) that is form of spherical differing from the existing form of flat or cube has been designed and tested its practicability to replace the part in mechanical check with digital image from QA operation. Materials and Methods: If the distance maintains constant between source(target) and image detector with constant distance to the center of spherical type mechanical check device(SMCD), the size will be shown as a constant image at all times regardless of its direction exposed. For the test, two accurate hemispheres are made and put together which results in a sphere of the equilateral circle. Results: It enables a variety of implementation of the existing mechanical check using digital image as follows: congruity level of radiation field and light field, size accuracy of radiation field and collimation field, gantry rotation isocenter check, collimation rotation isocenter check, room laser accuracy check, collimation rotation angle check, couch rotation angle check, and more. Conclusion: It has proved its practicability in checking isocenter congruity level as real time at the time of simultaneous rotation between gantry and couch that is applied to the non-coplanar field, which had been hard to apply as a device formed of existing flat or cube.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.2
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• pp.131-141
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• 2007

Purpose: Try to compare dose distribution and lung dose of radiation treatment plan of the breast cancer that used Irregular Surface Compensator (ISC) and treatment plan that used a wedge filter. Materials and Methods: Established a treatment plan to be distributed over 95% of prescription dose (5,040 cGy) of the two tangent-half fields that used a wedge filter and ISC at a breast organization as made to breast cancer patient having an irregular surfaces after surgery. Compared high dose area and DVH, and verified a treatment plan as used film with rectangular phantom. Results: Maximum dose point in breast tissue appeared to 107.5% in case of tangent-half fields Tx plan that used a wedge filter, and lung volumes exposed above 20 Gy by 7.63%. In case of ISC, maximum dose point in breast tissue appeared to 106.4%, and lung volumes exposed above 20 Gy by 6.5%. The film measurement results that used phantom, 105$\sim$110% high dose region was distributed to the upper part and both edges of phantom. However in case of ISC, appeared by 100$\sim$105% dose conformity distribution. Conclusion: In general, the Irregular Surface Compensator (ISC) can improve the dose conformity of breast tissues, as well as reduced hot spots in the lung and in the breast. Such an advantage by using ISC technique is more beneficial for patients who have more irregular surfaces after surgery.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.2
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• pp.77-82
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• 2007

Purpose: This study investigates peripheral dose from physical wedge and dynamic wedge system on a multileaf collimator (MLC) equipment linear accelerator. Materials and Methods: Measurments were performed using a 2D array ion chamber and solid water phantom for a 10$\times$10 cm, source-surface distance (SSD) 90 cm, 6 and 15 MV photon beam at depths of 0.5 cm, 5 cm through dmax. Measurments of peripheral dose at 0.5 cm and 5 cm depths were performed from 1 cm to 5 cm outside of fields for the dynamic wedge and physical wedge 15$^\circ$, 45$^\circ$. Dose profiles normalized to dose at the maximum depth. Results: At 6 MV photon beam, the average peripheral dose of dynamic wedge were lower by 1.4% and 0.1%. At 15 MV photon beam, the peripheral dose of dynamic wedge were lower by maximum 1.6%. Conclusion: This study showed that dynamic wedge can reduce scattered dose of clinical organ close to the field edge and reduced treatment time. The wedge systems produce significantly different peripheral dose that should be considered in properly choosing a wedge system for clinical use.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.240-249
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• 2001

A high speed ultra-compact lens with a diffractive optical element (DOE) is designed, which can be applied to mobile communication devices such as IMT2000, PDA, notebook computer, etc. The designed hybrid lens has sufficiently high performance of less than f/2.2, compact size of 3.3 mm (1st surf. to image), and wide field angle of more than 30 deg. compared with the specifications of a single lens. By proper choice of the aspheric and DOE surface which has very large negative dispersion, we can correct chromatic and high order aberrations through the optimization technique. From Seidel third order aberration theory and Sweatt modeling, the initial data and surface configurations, that is, the combination condition of the DOE and the aspherical surface are obtained. However, due to the consideration of diffraction efficiency of a DOE, we can choose only four cases as the optimization input, and present the best solution after evaluating and comparing those four cases. On the other hand, we also report dramatic improvement in optical performance by inserting another refractive lens (so-called, field flattener), that keeps the refractive power of an original DOE lens and makes the petzval sum zero in the original DOE lens system. ystem.

• Korean Journal of Social Welfare
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• v.68 no.4
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• pp.199-224
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• 2016

This study is a research that investigated organization of case management practice at a mental health center. For organization research of case management practice, this study applied the research method of Institutional Ethnography, and analyzed 'work knowledge' and 'texts' data which were obtained through field work that lasted 3 months with 11 study participants. The analysis is not interpretation of the researcher, but it is work that assembles 'work knowledge' of field workers until they reach discovering institutions that organize case management practice. As a result of this study, case management practice of the mental health center was being standardized as 'a service that is biased towards symptom management without comprehensive and continual resources links' by new public management theory, bio-medicine discussion, 'standardization policy', 'treatment rate improvement policy', 'performance-based budget system', 'performance evaluation system' and 'continual linkage policy', mediating texts. This is a different outcome from usefulness of case management that is claimed to support politically.

• Information Systems Review
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• v.9 no.1
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• pp.105-120
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• 2007

With the fast development of the Internet and the increasing dependence on information infrastructures, companies are faced with various information security threats such as information leakages, modifications, and information breaches. South Korea is one of the leading countries in the Internet usage, but is ranked relatively low when it comes to information security. In fact, many Korean firms have suffered financial losses and damaged corporate images from the information security breaches. However, because of the difficulties in quantifying the costs of the information security breaches, Korean companies tend to delay their investment decisions on information security. The purpose of this study is to measure the cost of information security breach and the economic value of security investment using the event study methodology. Our results show that the announcement of an information security breach negatively influenced the market value of the corresponding company. The effect was statistically significant at the significance level of p=0.05. The breached companies lose, on average, 0.86% of their market values on the day of the announcement - an average loss in market capitalization of $55 million. On the other hand, the investment on information security had no effect on the stock price or the market value of the firm.

• Childhood Kidney Diseases
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• v.2 no.2
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• pp.178-182
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• 1998

Purpose : The conventional Whitaker test assesses the renal pelvic pressure response to a constant infusion rate of 10 mL/min in adult and 5 mL/min in children. We evaluated whether the infusion rate,5 mL/min is appropriate during Whitaker test in children. Materials and Methods : The study included 3 children with unilateral hydronephrosis, whose diuretic renography results were equivocal to define the presence of urinary obstruction. The kidneys were perfused at increasing flow rates from lmL/min. Results : There were intrapelvic pressure increases $26\;cmH_2O$ at 3 mL/min, $50\;cmH_2O$ at 2 mL/min and $80\;cmH_2O$ at 3 mL/min infusion rate, respectively. There was no need to increase the infusion rate over 4 mL/min to get a positive Whitaker test. Conclusion : Our experience with Whitaker test at variable low flow rates (1-5 mL/min) confirmed its usefulness in differentiating obstructive from nonobstructive uropathy. We recommend the increasing infusion rate from 1 mL/min during Whitaker test in children.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.8 no.2
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• pp.137-142
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• 2005

Purpose: To evaluate the safety, efficacy and technical problems of the endoscopic balloon dilatation of esophageal anomalies in children. Methods: The medical records of 8 children treated by endoscopic balloon dilatation for esophageal anomalies over a 10-year period at Pusan National University Hospital were reviewed retrospectively. The balloon catheter (Maxforce TTS or CRE, Boston Scientific Co., USA) was positioned across the area of narrowing by direct visualization. The balloon was slowly inflated with normal saline to specified pressures for each balloon and maintained for 60 seconds and then deflated. After 60 seconds pause, the procedure was repeated with a larger sized balloon (increments of 1 mm for each subsequent dilation) till effective dilatation was confirmed by direct visualization without complications. Results: Three male and five female were included and their mean age was 4.2 years. A total of 27 (average of 3.2 per patient) dilatation were performed. Underlying diseases of patients are postoperative stricture of esophageal atresia in 3 cases, esophageal ring in 2 cases, achalasia, corrosive esophagitis and hypertensive LES in one case respectively. The size of initial dilating balloon was chosen on the basis of the diameter of the narrowing determined by endoscopy. The first dilation in patients with severe esophageal stricture was made with a 6 mm sized balloon. Complications observed were esophageal perforation and respiratory holding during the procedure in one case respectively. Successful outcome was seen in 6 patients (75%). Conclusion: Endoscopic balloon dilatation can provide a safe and effective mean of treating esophageal anomalies in children and should be considered the treatment of choice in the initial management of those cases.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.173-178
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• 2014

In this study, we introduce ASM-based face recognition classifier and its design methodology with the aid of 2-dimensional 2-directional hybird preprocessing algorithm. Since the image of face recognition is easily affected by external environments, ASM(active shape model) as image preprocessing algorithm is used to resolve such problem. In particular, ASM is used widely for the purpose of feature extraction for human face. After extracting face image area by using ASM, the dimensionality of the extracted face image data is reduced by using $(2D)^2$hybrid preprocessing algorithm based on LDA and PCA. Face image data through preprocessing algorithm is used as input data for the design of the proposed polynomials based radial basis function neural network. Unlike as the case in existing neural networks, the proposed pattern classifier has the characteristics of a robust neural network and it is also superior from the view point of predictive ability as well as ability to resolve the problem of multi-dimensionality. The essential design parameters (the number of row eigenvectors, column eigenvectors, and clusters, and fuzzification coefficient) of the classifier are optimized by means of ABC(artificial bee colony) algorithm. The performance of the proposed classifier is quantified through yale and AT&T dataset widely used in the face recognition.