• 한국의료질향상학회지
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• 제20권1호
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• pp.60-73
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• 2014

Objectives: This study aims at decreasing spatial dose rate through work improvement whilst spatial dose rate is the cause of increasing personal exposure dose which occurs in the process of handling radioisotope. Methods: From February 2013 until July 2013, divided into "before" and "after" the improvement, spatial dose rate in laboratory of nuclear medicine was measured in gamma image room, PET/CT-1 image room, and PET/CT-2 image room as its locations. The measurement time was 08:00, 12:00 and 17:00, and SPSS 21.0 USA was opted for its statistical analysis. Result: The spatial dose rate at distribution worktable, injection table, the entrance to the distribution room, and radioisotope storage box, which had showed high spatial dose rate, decreased by more than 43.7% a monthly average. The distribution worktable, that had showed the highest spatial dose rate in PET/CT-1 image room, dropped the rate to 42.3% as of July. The injection table and distribution worktable in the PET/CT-2 image room also showed the decline of spatial dose rate to 89% and 64.4%, respectively. Conclusion: By improving distribution process and introducing proper radiation shielding material, we were able to drop the spatial dose rate substantially at distribution worktable, injection table, and nuclide storage box. However, taking into account of steadily increasing amount of radioisotope used, strengthening radiation related regulations, and safe utilization of radioisotope, the process of system improvement needs to be maintained through continuous monitoring.

• Radiation Oncology Journal
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• 제38권1호
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• pp.52-59
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• 2020

Purpose: To evaluate and compare the feasibilities of magnetic resonance (MR) image-based planning using synthetic computed tomography (sCT) versus CT (pCT)-based planning in helical tomotherapy for prostate cancer. Materials and Methods: A retrospective evaluation was performed in 16 patients with prostate cancer who had been treated with helical tomotherapy. MR images were acquired using a dedicated therapy sequence; sCT images were generated using magnetic resonance for calculating attenuation (MRCAT). The three-dimensional dose distribution according to sCT was recalculated using a previously optimized plan and was compared with the doses calculated using pCT. Results: The mean planning target volume doses calculated by sCT and pCT differed by 0.65% ± 1.11% (p = 0.03). Three-dimensional gamma analysis at a 2%/2 mm dose difference/distance to agreement yielded a pass rate of 0.976 (range, 0.658 to 0.986). Conclusion: The dose distribution results obtained using tomotherapy from MR-only simulations were in good agreement with the dose distribution results from simulation CT, with mean dose differences of less than 1% for target volume and normal organs in patients with prostate cancer.

• Journal of Radiation Protection and Research
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• 제43권3호
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• pp.97-106
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• 2018

Background: A cargo container scanner using a high-energy X-ray generates a fan beam X-ray to acquire a transmitted image. Because the generated X-rays by LINAC may affect the image quality and radiation protection of the system, it is necessary to acquire accurate information about the generated X-ray beam distribution. In this paper, a diode-based multi-channel spatial dose measuring device for measuring the X-ray dose distribution developed for measuring the high energy X-ray beam distribution of the container scanner is described. Materials and Methods: The developed high-energy X-ray spatial dose distribution measuring device can measure the spatial distribution of X-rays using 128 diode-based X-ray sensors. And precise measurement of the beam distribution is possible through automatic positioning in the vertical and horizontal directions. The response characteristics of the measurement system were evaluated by comparing the signal gain difference of each pixel, response linearity according to X-ray incident dose change, evaluation of resolution, and measurement of two-dimensional spatial beam distribution. Results and Discussion: As a result, it was found that the difference between the maximum value and the minimum value of the response signal according to the incident position showed a difference of about 10%, and the response signal was linearly increased. And it has been confirmed that high-resolution and two-dimensional measurements are possible. Conclusion: The developed X-ray spatial dose measuring device was evaluated as suitable for dose measurement of high energy X-ray through confirmation of linearity of response signal, spatial uniformity, high resolution measuring ability and ability to measure spatial dose. We will perform precise measurement of the X-ray beamline in the container scanning system using the X-ray spatial dose distribution measuring device developed through this research.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.172-175
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• 1997

Outline contour is detected firstly to simulate dose distribution in radiation therapy planning system. In this paper, we developed automatic contour detection system using temporal and spatial relationships of image sequences. The low level image analysis involves the use of directional gradient edge operators and Laplacian operator. The High level portion of algorithm uses a knowledge-based strategy that incorporates fuzzy resoning method.

• 한국정보통신학회논문지
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• 제20권10호
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• pp.2001-2006
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• 2016

감마선 공간 탐지 장치는 감마선원을 스캔하여 영상화 한 후 스테레오 영상처리기술을 적용하여 탐지선원까지의 거리를 측정한다. 또한 실제 공간의 방사선원에 대한 분포 정보를 제공해 준다. 본 논문에서는 감마선 탐지장치가 3차원 공간상에서 장치로부터 선원을 찾기 위해 스캔하는 탐지 시간을 단축 시킬 수 있도록 감마선 탐지 고속화 알고리즘을 구현하였다. 그리고 감마선 조사 시험장에서 실험을 통해 그 성능을 검증하였다. 탐지시험 결과 고속 탐지를 위한 알고리즘을 적용할 경우 단일선원을 탐지할 경우 좌 우 스테레오 영상 획득 시보다 약 35% 의 탐지 시간을 단축시킬 수 있음을 확인하였다. 또한 사용자에게 방사선 공간분포 정보를 효율적으로 전달하기 위한 감마선원 분포의 입체 가시화를 구현하여 방사선원에 대한 정보를 제공할 수 있도록 하였다.

• Radiation Oncology Journal
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• 제3권1호
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• pp.59-64
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• 1985

Computation of three dimensional dose distribution using CT image and RT plan was applied to a case of pituitary adenoma. Algorithm was based on two dimensional Tissue Maximun Ratio model extended to the third dimension. The resulting isodose curve of transeverse, coronal and sagittal section was demonstrated. This RT plan allows computation of dose distribution in any arbitarily defined plane in addition to conventional cross sectional view.

• 한국의학물리학회지:의학물리
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• 제24권1호
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• pp.41-47
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• 2013

부피효과를 가지는 2차원 배열형 이온함으로부터 측정된 세기조절방사선치료의 선량분포와 부피효과를 가지지 않는 장치로부터 측정된 선량분포를 비교함으로써 이 효과가 측정결과에 미치는 영향에 대해 평가하였다. 조사면 크기에 따라 총 5개의 세기조절방사선치료계획을 5문 조사방식으로 가상의 팬톰에 시행하였다. 선량분포 측정은 매트릭스 팬톰, 빔 영상시스템, 필름 등 총 3가지 측정장치를 이용하였다. 측정된 값은 분석프로그램을 이용하여 전산화치료계획 시스템을 통해 획득된 선량분포와 비교하였다. 비교된 선량분포는 분석프로그램 상에서 상관계수와 감마값을 통해 측정장치의 부피효과 유무에 따른 차이를 분석한 결과 매트릭스 팬톰에서 최대 1.3% 이상으로 나타났다. 매트릭스 팬톰은 조사면의 크기가 작아질수록 내부의 이온함에 의해 부피효과가 커지게 되므로 다른 측정장치에 비해 더 큰 측정오차를 가지는 것으로 판단되었다.

• 대한방사선치료학회지
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• 제11권1호
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• pp.43-48
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• 1999

Purpose : For practical application of the MR image for stereotactic radiosurgery, the target point achieved by acquisition of MR image in a relatively homogeneous phantom has to agree with the actual isocenter of irradiation in real radiosurgery and the amount of distortion of the MR image should be known. Materials and Methods : A dosimetric film with a random target point was inserted into a radish vertically and horizontally on axis Z and they were fixed with a headring. After image acquisition by stereotactic radiosurgery planning system, we achieved stereotactic coordinate of the target point and examined irradiation using the coordinate acquired as isocenter. After the irradiation, the film in the radish was developed and processed and the degree of coincidence between the target point marked on the film and the center of the radiation distribution. In order to measure the degree of distortion of the MR image in a different way, an acryl phantom was made and punctures were made at intervals of 1 cm and a drop of oil was dropped into it. Then, it was inserted into the radish vertically and horizontally on axis Z to acquire the MR image. Each coordinate was achieved and the estimation of distortion of MR image was made both in vertical and horizontal directions Results : The film from the radio was developed and for the one inserted vertically on axis Z, there was a good coincidence in the discrepancy between the target point marked on the film and the center of the radiation distribution. For the one inserted horizontally, the discrepancy between them was under 0.5 mm. As a result of estimating distortion of MR image using acryl, the discrepancy was under 0.45 mm in the case of the phantom inserted vertically on axis Z, and that of the one inserted horizontally was 1.4 mm. Conclusion : We were able to confirm good coincidence in homogeneous phantom in actual treatment position of radiosurgery using the MR image and the discrepancy measured in the analysis of distortion of the MR image did not exceed the permissible level. Therefore, it was evident the system of the hospital is suitable for radiosurgery using MR image.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.328-328
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• 2007

Large area matrix-addressed image detectors are a recent technology for x-ray imaging with medical diagnostic and other applications. The imaging properties of x-ray pixel detectors depend on the quantum efficiency of x-rays, the generated signal of each x-ray photon and the distribution of the generated signal between pixels. In a phosphor coated detector the light signal is generated by electrons captured in the phosphor screen. In our study we simulated the lateral spread distributions for phosphor coupled detector by Monte Carlo simulations. Most simulations of such detectors simplify the setup by only taking the conversion layer into account neglecting behind. The Monte Carlo code MCNPX has been used to simulate the complete interaction and subsequent charge transport of x-ray radiation. This has allowed the analysis of charge sharing between pixel elements as an important limited factor of digital x-ray imaging system. The parameters are determined by lateral distribution of x-ray photons and x-ray induced electrons. The primary purpose of this study was to develop a design tool for the evaluation of geometry factor in the phosphor coupled optical imaging detector. In order to evaluate the spatial resolution for different phosphor material, phosphor geometry we have developed a simulation code. The developed code calculates the energy absorption and spatial distribution based on both the signal from the scintillating layer and the signal from direct detection of x-ray in the detector. We show that internal scattering contributes to the so-called spatial resolution drop of the image detector. Results from the simulation of spatial distribution in a phosphor pixel detector are presented. The spatial resolution can be increased by optimizing pixel size and phosphor thickness.

• 대한방사선기술학회지:방사선기술과학
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• 제11권2호
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• pp.3-15
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• 1988

When X-rays were projected into a patient, there occured the phenomena such as penetration, absorption and scattering etc. The penetrating rays were recorded on films as X-ray image used for diagnosis but scattered rays caused the radiation hazard both to the patient, specialist and technicians. The soft tissue includes many organs which are sensitive to the radiation and in may occupy $40{\sim}50%$ of body weight. Therefore X-rays should be carefully projected to the patient and it is strongly recommended to analyse the distribution of X-rays, when ever the patient is exposed to X-rays. In this study, the distribution of X-ray according to the thickness, the radiation field and the tube voltages (kVp) in soft tissue, the following results were obtained: 1. Total transmitted rays which kept the step with X-ray tube voltage (kVp) increased in proportion to the increasing of X-ray tube voltage. 2. The scattered ray rate in the total transmitted ray was not significantly found with X-ray tube voltage. 3. The affecting factors of the scattered ray rate in total transmitted ray were shown through the radiation field and the thickness. 4. The dose of scattered ray by the angle was observed more in direction of primary ray ($0^{\circ}$) and back scattering ($160^{\circ}$) than in direction of $90^{\circ}$. 5. The more the distance from phantom to the patient should be less distribution of scattered ray.