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조영 전후의 폐 CT 영상 정합을 위한 특징 기반의 비강체 정합 기법
이현준,홍영택,심학준,권동진,윤일동,이상욱,김남국,서준범,Lee, Hyun-Joon,Hong, Young-Taek,Shim, Hack-Joon,Kwon, Dong-Jin,Yun, Il-Dong,Lee, Sang-Uk,Kim, Nam-Kug,Seo, Joon-Beom 대한의용생체공학회 2011 의공학회지 Vol.32 No.3
In this paper, a feature-based registration technique is proposed for pre-contrast and post-contrast lung CT images. It utilizes three dimensional(3-D) features with their descriptors and estimates feature correspondences by nearest neighborhood matching in the feature space. We design a transformation model between the input image pairs using a free form deformation(FFD) which is based on B-splines. Registration is achieved by minimizing an energy function incorporating the smoothness of FFD and the correspondence information through a non-linear gradient conjugate method. To deal with outliers in feature matching, our energy model integrates a robust estimator which discards outliers effectively by iteratively reducing a radius of confidence in the minimization process. Performance evaluation was carried out in terms of accuracy and efficiency using seven pairs of lung CT images of clinical practice. For a quantitative assessment, a radiologist specialized in thorax manually placed landmarks on each CT image pair. In comparative evaluation to a conventional feature-based registration method, our algorithm showed improved performances in both accuracy and efficiency.
최근 10년간 천식환자에서 흡입 스테로이드제 처방 빈도와 중증 악화 빈도의추세 분석
노창석 ( Chang Suk Noh ),이재승 ( Jae Seung Lee ),송진우 ( Jin Woo Song ),김태범 ( Tae Bum Kim ),김남국 ( Nam Kug Kim ),조유숙 ( You Sook Cho ),이상도 ( Sang Do Lee ),문희범 ( Hee Bom Moon ),오연목 ( Yeon Mok Oh ) 대한결핵 및 호흡기학회 2011 Tuberculosis and Respiratory Diseases Vol.70 No.5
Background: Inhaled corticosteroids (CSs) are the most essential medication for asthma control. Many reports suggest that the usage of ICSs improves not only the control of asthma symptoms but also prevents exacerbation. We investigated whether increases in ICS prescriptions are associated with decreases in asthma exacerbation in the clinical practice setting. Methods: We retrospectively analyzed the database of adult asthma patients who had visited a tertiary referral hospital, the Asan Medical Center between January 2000 and December 2009. The number of emergency department (ED) visits, admissions, intensive care unit (ICU) care, deaths, and ICS prescriptions were analyzed to evaluate the time trend of asthma exacerbation as a function of the ICS prescription rate during the ten years. Results: The numbers of ED visits, admissions, and episodes of ICU care decreased during the ten years (p<0.001, p=0.033, p=0.001, respectively) while the number of ICS prescriptions increased (p<0.001). We found a correlation between the number of ICS prescriptions and the number of ED visits, admissions, or ICU care. For these outcomes, the correlation coefficients were r=-0.952, p<0.001; r=-0.673, p=0.033; r=-0.948, p<0.001, respectively. Conclusion: The number of ICS prescriptions increased during the past ten years while the number of asthma exacerbations decreased. Our results also showed a negative correlation between the ICS prescription rate and asthma exacerbation in the clinical practice setting. In other words, an increase in ICS prescription may be a major cause of a decrease in asthma exacerbations.
Kim, Nam-Kug,Park, Jae-Woo,Chang, Young-Il 대한치과교정학회 발행 2005 대한치과교정학회지 Vol.35 No.6
This study was performed to investigate the reproducibility of the horizontal and midsagittal planes, and to suggest a stable coordinate system for three-dimensional (3D) cephalometric analysis. Eighteen CT scans were taken and the coordinate system was established using 7 reference points marked by a volume model, with no more than 4 points on the same plane. The 3D landmarks were selected on V works (Cybermed Inc., Seoul, Korea), then exported to V surgery (Cybermed Inc., Seoul, Korea) to calculate the coordinate values. All the landmarks were taken twice with a lapse of 2 weeks. The horizontal and midsagittal planes were constructed and its reproducibility was evaluated. There was no significant difference in the reproducibility of the horizontal reference planes. But, FH planes were more reproducible than other horizontal planes. FH planes showed no difference between the planes constructed with 3 out of 4 points. The angle of infersection made by 2 FH planes, composed of both Po and one Or showed less than 1° difference. This was identical when 2 FH planes were composed of both Or and one Po. But, the latter cases showed a significantly smaller error. The reproducibility of the midsagittal plane was reliable with an error range of 0.61 to 1.93° except for 5 establishments (FMS-Nc, Na-Rh, Na-ANS, Rh-ANS, and FR-PNS). The 3D coordinate system may be constructed with 3 planes; the horizontal plane constructed by both Po and right Or; the midsagittal plane perpendicular to the horizontal plane, including the midpoint of the Foramen Spinosum and Nc; and coronal plane perpendicular to the horizontal and midsagittal planes, including point clinodale, or sella, or PNS. 본연구는 삼차원 두부 영상을 위치시키기 위한 좌표계를 구성하는 방법에 대한 제안하기 위해, CT data에서 기존의 두부방사선 계측사진에서 쓰이는 점들을 선정하고, 이를 바탕으로 수평, 수직평면의 안정성을 조사하였다. 서울대학교 치과병원에 내원한 환자 18명의 CT자료를 채득하였으며, 모든 환자는 서울대학교 병원 진단방사선과에서 촬영하였다. (Somatom Plus 4: Siemens, Eriange, Germany). V works for surgery 4.0 (Cybermed Inc., Seoul, Korea)을 이용하여 3차원 좌측표를 선정하고, 계측점을 선택하였다. 좌표축을 동일하게 설정하기 위해 7개의 점(reference point)을 4·4·2 pixel size의 voxel로 따로 표시하였다. 계측점을 선정한 후 V surgery (Cybermed Inc., Seoul, Korea)에서 각 점의 좌표값을 추출하였다. 각각의 점들은 2회 반복 선정한 후 점들을 조합하여 수평, 수직평면의 재현성을 평가한 결과 다음과 같은 결론을 얻었다 수평 기준면의 재현도는 S-CI평면을 제외하고는 통계적으로 유의한 차이를 보이지 않았으나, 사잇각은 FH평면이 가장 작게 나타났다. FH평면은 Po과 Or중 어느 3점을 선택하더라도, 통계적으로 유사한 재현도를 보였다. FH1과 FH2의 사잇각과 FH3과 FH4의 사잇각은 1° 이하의 적은 오차를 보이며, FH3과 FH4의 사잇각이 통계적으로 더 작은 차이를 보였다. 정중시상면의 재현도는 FMS-Nc, Na-Rh, Na-ANS, Rh-ANS, FR-PNS를 기준으로 설정한 경우를 제외하면, 0.61~1.93° 의 양호한 값을 보였다. 이상의 결과에 의하면 공간에서 정의되는 평면의 재현도는 평면을 정의하는 점 자체의 식별오차뿐 아니라, 각 점의 위치관게에도 영향을 받는 것을 알 수 있었다. 따라서, 안정적인 3차원 기준좌표계를 구성하려면 양측 Po과 편측 Or으로 구성되는 평면을 수평기준면으로, 수평면에 수직이고, Foramen Spinosum의 중점과 Nc를 포함하는 평면을 수직기준면으로, 수평면과 수직면에 수직이고, clinoidale나 sella, PNS를 지나는 평면을 전두면으로 설정하는 것이 바람직할 것으로 생각된다.
박재우,김남국,장영일 대한치과교정학회 2005 대한치과교정학회지 Vol.35 No.5
이 연구는 기존의 두부방사선사진에서 사용되었던 계측점들을 3차원으로 재구성한 CT자료에서 다시 정의하고, 그 점들의 재현도를 조사함으로써, 재현성이 높고 해부학적 특징을 잘 표현하는 점들을 제안하고자 시행하였다. 3차원 영상에서 상대적 좌표값을 구하기 위해 어느 4점도 같은 평면에 존재하지 않는 7개의 고정점을 선정하여 기준 좌표계를 설정하였다. V works 4.0 (Cybermed Inc., Seoul, Korea)을 이용하여 고정점과 Ⅰ점 설정을 위한 volume model (voxel size=4*4*2, threshold value = 639)을 형성한 후 계측점을 선택하였으며, 나머지 점들은 모두 volume mode의 MPR 창을 이용하여 선정하였다. 이렇게 선정한 계측점을 V surgery(Cybermed Inc., Seoul Korea)로 이출하여 각 점의 상대적 공간 좌표값을 구하였다. 모든 자료는 2주 간격으로 2번 측정한 후 재현도를 계산하였다. 각 계측점의 재현도는 x축 0.13~1.24mm. y축 0.23~1.53mm, z축 0.15~1.81mm로 유사한 범위를 보였다. 재현도가 우수한 것은 고정점을 이용한 I점이며 봉합에 의해 정의되는 J점의 재현도가 비교적 낮게 나타났다. 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 0.17~1.21 mm in the x axis, 0.30~1.53 mm in the y axis, and 0.27~1.81 mm 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 I points which were selected on the basis of the volume model. The least reproducible points were J points that were defined by sutures.