정책분석에 있어서의 정책정보

윤석환 충남대학교 대학원 1990 論文集 Vol.11 No.-

For IoT Data Services Private Cloud Server [OnBiz Cube]

윤석환 대한전자공학회 2016 대한전자공학회 학술대회 Vol.2016 No.6

68Ga-DOTATOC PET/CT에서 Prompt Gamma Correction을 적용한 SUV의 평가

윤석환 한국방사선학회 2018 한국방사선학회 논문지 Vol.12 No.1

68Ga was eluted from a 68Ge/68Ga radionuclide generator. 68Ga decays into 68Zn, with a half life=67.8min. The decay is 88.9 % by β+ and 11.1 % by EC. The main β+ decay (87.7 %) is to the ground level of 68Zn and it is a pure positron emission branch. A small fraction decays β+ (1.2 %) into an excited level of 68Zn, which promptly decays into the ground level with a γ (1.077 Mev). This can constitute prompt gamma contamination in the PET data, if the 1.077 Mev γ has a scatter interaction in the patient, and generates a lower energy γ in coincidence with the positron annihilation pair. The purpose of this study was to evaluate standardized uptake value(SUV) before and after applying prompt gamma rays correction on 68Ga-DOTATOC PET/CT image. Fifty patient underwent PET/CT 1 hour after injection of the 68Ga-DOTATOC. The SUVmax and SUVmean of lesions and normal tissues (Pituitary, Lung, Liver, Spleen, Kidney, Intestine) were evaluated before and after applying prompt gamma correction on 68Ga-DOTATOC PET/CT image. Additionally, the SUVmax of each lesions and SUVmean of the soft tissues were measured on images. and target to background ratios (TBR) were calculated as quantitative indices. Among 15 patients, 25 of lesions (Pancreas, Liver, Thoracic Spine, Brain) with increased uptake on 68Ga-DOTATOC PET/CT image. SUVmax and SUVmean were increased in lesion site and normal tissue after prompt gamma rays correction. TBR was 51.51 ± 49.28 and 55.50 ± 53.12 before and after prompt gamma rays correction, respectively. (p<0.0001) 68Ga 방사성 핵종은 68Ge/68Ga 제너레이터에서 생산되는 양전자 방출핵종으로서 PET 검사에 이용되는 방사성 핵종이다. 68Ga은 67.8분의 반감기를 가지고 88.9 %의 β+ 붕괴와 11.1 %의 전자포획으로 68Zn으로 붕괴된다. β+ 붕괴 과정에서 87.7 %는 기저상태의 68Zn로 붕괴되며, 1.2 %는 여기상태의 68Zn로 붕괴된다. 여기상태의 68Zn은 1.077 Mev의 γ선을 방출하며 기저상태의 68Zn가 된다. 이때 방출되는 1.077 Mev의 γ선을 Prompt Gamma라 하며, Prompt Gamma-ray가 환자와 상호작용하게 되면 저에너지 γ선의 산란선이 발생되게 되는데 이 산란선이 PET의 동시계수 회로에 검출되어 질 수 있다. 이 연구의 목적은 68Ga을 이용하는 PET검사 중 신경내분비 종양진단에 사용되는 68Ga-DOTATOC PET/CT영상에 Prompt Gamma-ray 보정 전 후의 표준섭취계수(SUV)를 평가해 보고자 하였다. 68Ga-DOTATOC PET/CT를 시행한 15명의 환자에 대해서 병변부위(Pancreas, Liver, Thoracic Spine, Brain)와 정상으로 섭취되는 조직(Pituitary, Lung, Liver, Spleen, Kidney, Intestine)의 SUVmax와 SUVmean을 비교하였으며, 임상영상의 정량적 평가를 위해 Target to Background Ratio(TBR)을 산출하여 비교하였다. Prompt Gamma-ray 보정 후 Thoracic Spine을 제외한 병변부위와 Pituitary를 제외한 정상조직에서 SUVmax, SUVmean은 높은 값을 나타내었으며, TBR은 Prompt Gamma-ray 보정 전 후 각각 51.51±49.28, 55.50±53.12로 보정 후 높은 값을 나타냈다. (p<0.0001)

지리정보 데이터 압축률 향상을 위한 Run-Length/Byte-Packing 압축 알고리즘 설계 및 구현

윤석환,양승수,박석천,Yoon, Seok-Hwan,Yang, Seung-Su,Park, Seok-Cheon 한국정보통신학회 2017 한국정보통신학회논문지 Vol.21 No.10

최근 압축 알고리즘이 지리정보 데이터를 압축하기 위한 방법으로 가장 많이 사용되고 있다. 그러나 이와 같은 압축 알고리즘은 지리정보 데이터 압축에 실제 적용하기에는 지도 데이터의 연속성이 미흡하고, 단일 데이터로 압축할 수 없기 때문에 압축률이 저하된다는 문제점이 있다. 따라서 본 논문에서는 이러한 문제점을 개선하기 위해 압축 알고리즘들의 장점을 취합해 지리정보 데이터 압축을 가능하게 하고, 압축 및 복원 속도를 향상시킨 Run-Length/Byte-Packing 압축 알고리즘을 설계 및 구현하였다. 구현한 알고리즘을 평가한 결과 기존 압축 알고리즘에 비해 제안 알고리즘이 평균 약 5% 향상된 것을 확인하였으며, 압축률과 복원 속도가 향상되었다는 것을 확인하였다. Recently, a compression algorithm is widely used as a method for compressing geographic information data. However, such a compression algorithm has a problem that the continuity of the map data is insufficient to actually apply it to the geographic information data compression, and the compression rate is lowered because it can not be compressed into a single data. Therefore, in this paper, we have designed and implemented a Run-Length / Byte-Packing compression algorithm that enables compression of geographic information by combining the advantages of compression algorithms and improves compression and restoration speed. As a result of evaluating the implemented algorithm, it was confirmed that the proposed algorithm improved about 5% on average compared with the existing compression algorithm, and it was confirmed that the compression rate and the restoration speed were improved.

18F-FDG PET/CT 융합영상에서 영상 재구성 차이에 의한 MTV (Metabolic tumor volume) 평가

윤석환 한국융합학회 2018 한국융합학회논문지 Vol.9 No.1

FDG PET 영상에서 MTV는 종양의 전체 대사정도를 반영하여 종양의 체적을 나타낸다. 하지만 MTV는 영상재구성의 영향을 받게 된다. 본 연구의 목적은 팬텀실험을 통하여 영상재구성에 따라 SUVmax의 역치 값을 달리하여 실제 체적과 MTV의 상관관계를 평가해보고자 하였다. NEMA IEC Body 팬텀에 18F-FDG를 구와 배후 방사능의 비율(4:1, 8:1, 10:1, 20:1)이 되도록 주입 후 영상을 획득하였다. 획득한 영상에 4가지 방법(OSEM3D, OSEM3D+PSF, OSEM3D+TOF, OSEM3D+TOF+PSF)으로 영상을 재구성한 후 다양한 SUVmax 역치 값을 적용하여 MTV의 변화를 비교해 보았다. 전반적으로 SUVmax 역치 값이 증가 할수록 MTV가 감소하였으며, 구와 배후방사능 비율이 증가할수록 동일한 SUVmax 역치 값에서 MTV가 감소하였다. PSF와 TOF+PSF재구성영상에서 40% 역치 값, OSEM3D와 TOF 재구성 영상에서는 45% 역치 값을 적용하였을 때 팬텀의 실제체적과 MTV의 높은 상관관계를 보였다. 이번 연구결과를 통하여 영상재구성에 따라 MTV 측정에 기초적인 자료로 제공되어 질 것으로 사료된다. Recently, MTV(metabolic tumor volume) has been used as indices of the whole tumor FDG uptake on FDG PET image but it is influenced by image reconstruction. The purpose of this study was to evaluate the correlation between actual volume and metabolic tumor volume applying different SUVmax threshold for different reconstruction algorithm on phantom study. Measurement were performed on a Siemens Biograph mCT40 using a NEMA IEC body phantom containing different size six spheres filled with F18-FDG applying four SBRs (4:1, 8:1, 10:1, 20:1). Images reconstructed four algorithms (OSEM3D, OSEM3D+PSF, OSEM3D +TOF, OSEM3D+TOF+PSF) and MTV were measured with different SUVmax threshold. Overall, the use of increasing thresholds result in decreasing MTV. and increasing the signal to background ratio decreased MTV by applying same SUVmax threshold. The 40% SUVmax threshold gave the best concordance between measured and actual volume in PSF and PSF+TOF reconstruction image. and the 45% threshold had the best correlation between the volume measured and actual volume in OSEM3D and TOF reconstruction image. we believe that this study will be used when the measurement of MTV applying various reconstruction image.

자성나노입자와 자기력을 이용한 세포 조절

윤석환 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.4

상수도용 도복장간관의 용접 및 외부하중에 의한 응력 특성에 관한 연구(II) - 복합외부하중 및 후열처리에 따른 용접부의 응력분포 특성 -

윤석환,이승기,나석주,고명환 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.3

One of the major characteristics that affects the life of welded steel water pipes is the stress distribution caused by welding and external forces. Some studios have bean carried out on the residual stress of steel water pipes. But the results on the stress distributions by welding and complex external forces are rare, because real water pipes operate under the ground and many kinds of external forces act simultaneously on the joints. To understand the complex stress distributions of welded joints, therefore predictions by numerical or analytic methods are required. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Based on these results, stress distributions by welding and complex external forces are evaluated by adopting the same numerical method. The influence of some post weld heat treatments on residual stress distributions is also investigated.

농지 소유 및 이용 구조와 정책 논리

윤석환 (사)농정연구센터 2019 농정연구 Vol.68 No.-

클러스터링 성능평가: 신경망 및 통계적 방법

윤석환,신용백 한국기술사회 1996 技術士 Vol.29 No.2

This paper evaluates the clustering performance of a neural network and a statistical method. Algorithms which are used in this paper are the GLVQ(Generalized Loaming vector Quantization) for a neural method and the k -means algorithm for a statistical clustering method. For comparison of two methods, we calculate the Rand's c statistics. As a result, the mean of c value obtained with the GLVQ is higher than that obtained with the k -means algorithm, while standard deviation of c value is lower. Experimental data sets were the Fisher's IRIS data and patterns extracted from handwritten numerals.

치과 임플란트 치료를 위한 평행광 CT의 움직임 에러 수정

윤석환,김성균,허성주,곽재영,임재홍,노승준,전경택 대한구강악안면임플란트학회 2020 대한구강악안면임프란트학회지 Vol.24 No.2

The purpose of this study is to correct the errors that may occur because of the patients' movement during the CT scanning, and thus, to obtain more precise CT images, additionally to investigate the possible use of parallel Beam CT in the dental treatment. Materials and Methods: Applying the Radon transform using phantom image, the same image and the sinogram with the ones by CT scanning were obtained. The possible movement errors that patients may cause during the CT scan were given to the data images. The maximum width of errors was designed to reach 1 mm. The fixed point was identified in the errored CT projected images, and each projected image with errors was adjusted so that each fixed point is placed on the same axial plane, then the fixed point was traced on the sinogram. On the traced trajectory of the fixed point, the part deviated from the sinusoidal curve was modified using the Virtual Alignment Method. Results: The quality of reconstructed image was remarkably degraded when the movement errors were given. The movement errors were corrected by moving the fixed point to the center of sinogram and this relocation of fixed point did not cause any distortion of image or change of size. Conclusion: The movement errors during CT scanning were corrected using the fixed point inside of the image. The more precise CT images obtained through this method are expected to be of extensive application in the area of dental implantology.