• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.189-191
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• 2002

In the proton therapy using a gantry system, periodical verification of iso-center position is very important to assure precision of patient positioning system at any gantry angles in proton treatment. In the gantry system, there are three different types of iso-center; 1) in a geometrical view, 2) in an X-ray beam's eye view, 3) in a proton beam's eye view. Idealistically, they would be an identical point. They could, however, be different points. It may be a source of errors in patient positioning. At PMRC, we have established a system of verification for iso-center positions using a stainless ball of 2-cm in diameter and an imaging plate. This system provides the relation among a center of a patient target position, a center of proton irradiation field, and/or a center of X-ray field in accuracy of 50$\square$m in the 2) and 3) views, as images of a center of the stainless ball and a center of a 100 mm${\times}$100 mm-aperture brass collimator recorded on the imaging plate, which is setup at 1-cm behind the ball. In addition, it provides simultaneously the images of the ball and the collimator on an imaging intensifier (II), which is setup downstream of the proton or X-ray beam. We present a method of quality assurance (QA) for calibration of iso-center position in a rotation gantry system at PMRC and the performance of this system. A proton beam position on the 1$\^$st/ scatterer in the nozzle of the gantry affects less sensitive (reduced by a factor of 1/5) to the results of the iso-center position. The effect is systematically correctable. The effect of the nozzle (or the collimator) position is less than 0.5 mm at the maximum extraction (390 mm).

• Clinical and Experimental Pediatrics
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• 제61권7호
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• pp.226-230
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• 2018

Purpose: This pilot study assessed changes in the growth plate and growth rates in children during a 6-month period. Methods: The study included 31 healthy children (17 boys, 14 girls) under evaluation for growth retardation. Height, weight, bone age, insulin like growth factor-1 (IGF-1), and insulin like growth factor binding protein 3 (IGF-BP3) were measured at baseline and after 6 months. In addition, the diameter, thickness, and volume of the femoral and tibial growth plates were measured using magnetic resonance imaging. Results: The mean bone age in boys and girls was 11.7 and 10.7 years, respectively. In boys, height (z score) (-0.2 vs. 0.0), weight (z score) (0.8 vs. 1.1), body mass index (BMI) (z score) (1.27 vs. 1.5), IGF-1 (ng/mL) (343.6 vs. 501.8), and IGF-BP3 (ng/mL) (5,088.5 vs. 5,620.0) were significantly higher after 6 months. In girls, height (z score) (-1.0 vs. -0.7), weight (z score) (-0.5 vs. 0.1), BMI (z score) (-0.02 vs. 0.3), IGF-1 (ng/mL) (329.3 vs. 524.6), and IGF-BP3 (ng/mL) (4,644.4 vs. 5,593.6) were also significantly higher after 6 months. In both sexes, the mean diameter and volume of the femoral and tibial growth plates were significantly increased 6 months later. Conclusion: No significant correlation was found between changes in the growth plate and clinical parameters in children with growth retardation in this study, other than correlations of change in femoral diameter with weight and BMI. A larger, long-term study is needed to precisely evaluate the correlation between change in the growth plate and growth.

• 한국임상수의학회지
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• 제41권3호
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• pp.157-164
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• 2024

The standard radiation protection method in the angiography suite involves the use of a thyroid shield, a lead apron, and lead glasses. However, exposure to substantial amounts of ionizing radiation can cause cataracts, tumors, and skin erythema. A newly developed curtain-type radiation protection device consists of a curtain drape composed of a five-layer bismuth and lead acrylic head-shielding plate, with both bearing an equivalent 0.25 mm lead thickness. In this study, a quality assurance phantom was used as the patient to create radiation scatter from the radiographic source, and an anthropomorphic mannequin phantom was used as the interventionalist to measure the radiation dose at seven different anatomical locations. Thermoluminescent dosimeters were used to measure the radiation dose. The experimental groups consisted of all-sided or one-sided curtain set-ups, the presence or absence of a conventional shielding system, and the orientation of beam irradiation. Consequently, the curtain-type radiation protection device exhibited better radiation protection range and capabilities than conventional radiation protection systems, especially in safeguarding the forehead, eyes, arms, and feet, with minimal radiation exposure. Moreover, the mean shielding ratios of the conventional shielding system and curtain-type radiation protection device were measured at 51.94% and 93.86%, respectively. Additionally, no significant decrease in the radiation protection range or capability was observed, even with changes in the beam orientation or one-sided protection. Compared with a conventional shielding system, the curtain-type radiation protection device decreased radiation exposure doses and improved comfort. Therefore, it is a potential new radiation protection device for veterinary interventional procedures.

• Journal of Radiation Protection and Research
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• 제29권4호
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• pp.231-236
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• 2004

시료중의 방사능 분포를 영상으로 획득할 수 있는 2차원 디지털 방사선 검출기인 Imaging Plate(IP) 검출기는 주로 산업용 라디오그라피, 의료진단, X-선 회절실험 등에서도 광범위하게 사용되고 있다. 본 연구에서는 IP 검출기의 여러 종류의 방사선에 대한 높은 감도 우수한 공간 분해능, 넓은 선형범위와 스크린의 높은 균질성을 이용하여 시료중의 방사능을 측정할 수 있는 가능성에 대해 조사하였다. 먼저 IP 검출기를 이용하여 면적선원의 표면균질도 측정에 적용하였다. 상용 기준 면적선원$(^{241}Am)$의 방사능 분포에 대한 영상을 얻어서 표면 균질도를 비 파괴적이고 신속하게 측정하였다. 다음으로 IP 검출기를 극저준위 방사능 측정에 적용하여 방사능 측정가능성에 대해 연구하였다. 이를 위해 IP 검출기의 스크린 균질도, 배경방사선 차폐효과, 선형범위 조사, fading 시간을 조사하였다. 극저준위 방사능 측정을 위해 감자 바나나 무 당근에 포함되어 있는 $^{40}K$ 자연방사능을 선택하여 측정하였다. 기준선원을 사용하여 IP 효율교정을 수행하였다.

• 대한디지털의료영상학회논문지
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• 제8권1호
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• pp.33-38
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• 2006

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.242-242
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• 2003

• Current Optics and Photonics
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• 제5권1호
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• pp.8-15
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• 2021

An elliptical zone plate (EZP) array is important in off-axis optical systems because it provides two advantages. First, the residual beam and the main source are not focused in the same direction and second, the light from the observation plane is not reflected back towards the beam source. However, the fill factor of the previous EZP array was about 76% which was a little low. Hence, this EZP array could not collect the maximum amount of illumination light, which affected the overall optical performance of the lens array. In this study, we propose a new EZP array design with a 97.5% fill factor used in off-axis imaging system for enhancement of brightness and contrast. Then, direct laser lithography was used to fabricate the high fill factor EZP array by moving the XY linear stage of the system in a zigzag motion. The imaging properties of the proposed EZP array were experimentally verified at the focal plane and compared with the previous model.

• 한국광학회:학술대회논문집
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• 한국광학회 1997년도 Advance Program of 14th optics andquantum Electronics conference, 1997제14 회 광학 및 양자전자 학술 발표회 논문 요약집
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• pp.61-61
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• 1997

• Journal of information and communication convergence engineering
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• 제8권5호
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• pp.581-585
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• 2010

A grid was sandwiched between two cascaded imaging plates. Using a fan-beam X-ray tube and a single exposure scheme, the two imaging plates, respectively, recorded grid-less and grid type information of the object. Referring to the mathematical model of the Grid-less and grid technique, it was explained that the collected components whereas that of imaging plates with grid was of high together with large scattered components whereas that of imaging plate with grid was of low and suppressed scattered components. Based on this assumption and using a Gaussian convolution kernel representing the effect of scattering, the related data of the imaging plates were simulated by computer. These observed data were then employed in the developed post-processing estimation and restoration (kalman-filter) algorithms and accordingly, the quality of the resultant image was effectively improved.

• 비파괴검사학회지
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• 제29권4호
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• pp.338-343
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• 2009

토모그래피는 다중 빔을 이용하여 단면을 영상화하는 기법으로서 주로 의료진단 분야에서 인체의 단면 영상획득을 위해 응용되어지는 기법이다. 비파괴검사 분야에서도 단순한 시간영역 신호의 제시에서 탈피하여 검사자에게 영상을 제공함으로써 진단의 효율성을 높이고자 하는 추세이므로 이 기법은 많은 의미를 갖는다. 최근, 유도초음파를 이용한 평판 구조물의 진단 기법이 많은 주목을 받고 있어, 본 논문에서는 컴퓨터 기반 유도초음파 해석 기법과 토모그래피 영상화 기법을 기반으로 2차원 평판에 존재하는 결함 위치를 영상화하는 연구를 수행하였다. 이를 위해 경계요소법을 이용하여 판 구조물에 존재하는 결함이 유도초음파의 전파 양상에 미치는 영향을 해석하고 그 결과를 토모그래피 영상화 기법에 적용하여 평판의 결함 위치를 판별하고자 하였다. 그 결과, 토모그래피를 위해 사용되는 센서의 개수가 결함 검출 성능에 많은 영향을 미침을 확인할 수 있다.