• Journal of Biomedical Engineering Research
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• v.27 no.3
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• pp.110-116
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• 2006

Finite element method (FEM) provides several advantages over other numerical methods such as boundary element method, since it allows truly volumetric analysis and incorporation of realistic electrical conductivity values. Finite element mesh generation is the first requirement in such in FEM to represent the volumetric domain of interest with numerous finite elements accurately. However, conventional mesh generators and approaches offered by commercial packages do not generate meshes that are content-adaptive to the contents of given images. In this paper, we present software that has been implemented to generate content-adaptive finite element meshes (cMESHes) based on the contents of MR images. The software offers various computational tools for cMESH generation from multi-slice MR images. The software named as the Content-adaptive FE Mesh Generation Toolbox runs under the commercially available technical computation software called Matlab. The major routines in the toolbox include anisotropic filtering of MR images, feature map generation, content-adaptive node generation, Delaunay tessellation, and MRI segmentation for the head conductivity modeling. The presented tools should be useful to researchers who wish to generate efficient mesh models from a set of MR images. The toolbox is available upon request made to the Functional and Metabolic Imaging Center or Bio-imaging Laboratory at Kyung Hee University in Korea.

• Journal of radiological science and technology
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• v.26 no.1
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• pp.83-89
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• 2003

The accurate measurement of the femoral anteversion is very important to the practice of orthopedic and osteotomy. It is measured by means of the axis of head and neck of the femur and the knee axis. At the present time, widely used computed tomography method of measuring anteversion on femoral necks of patients. Measurement by the manual method and image viewer of computed tomography to determine the anteversion of femoral head were carried out on both femurs. In September and October 2002, 5 patients 28 to 36 years of age were randomly selected from Seoul National University Hospital. The purpose of this paper was to introduce a new method to measure femoral anteversion angle utilizing PACS image viewer program in the MR imaging. Significant difference was observed between the right and left side the image viewer measurement of femoral anteversion. In conclusion, MR imaging very usefulness in the measured the angle of the femoral anteversion.

• The Korean Journal of Nuclear Medicine
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• v.32 no.5
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• pp.414-424
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• 1998

Purpose: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. Materials and Methods: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. Results: Using our newly developed method, robust extraction of head boundary was possible and spatial registration was successfully performed. Mean displacement error was less than 2.0 mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. Conclusion: Our refined technique could practically enhance the performance of automated three dimensional coregistration.

• Progress in Medical Physics
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• v.28 no.4
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• pp.190-196
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• 2017

For the $ViewRay^{(R)}$ system (ViewRay Inc., Cleveland, OH, USA) which is representative of magnetic resonance (MR) guided radiotherapy machine, it is important to evaluate effectiveness of AAPM's TG-51 protocol and the effect of the magnetic field on absolute dosimetry. In order to measure the absolute dose, MR-compatible chamber and water phantom system manufactured in this study were used. The materials of the water phantom system were plastic of polymethyl methacrylate (PMMA) and non-ferrous materials. Due to the inherent feature of the $ViewRay^{(R)}$, all Co-60 sources are not located at gantry angle of $0^{\circ}$ while being located at gantry angle of $90^{\circ}$. For this reason, absolute dosimetry was performed based on the measurements in solid water phantom (SWP) and water which determine the SWP to water correction factor. For evaluation of output constancy with gantry angle, measurements were made with ionization chamber inserted in cylindrical water-equivalent phantom. For measured doses in water, the values of dose deviation according to a reference dose of 200 cGy for Head 1, Head 2 and Head 3 were -0.27%, -0.45% and -0.22%, respectively. For measured doses in SWP, the values of dose deviation according to a reference dose of 200 cGy for Head 1, Head 2 and Head 3 were -1.91%, -2.07% and -1.84%, respectively. All values of dose measured in SWP tended to be less than those measured in water by -1.63%. With the reference gantry angles of $0^{\circ}$ and $90^{\circ}$, the maximum values of deviation for Head 1, Head 2 and Head 3 were 0.48%, 1.06% and 0.40%, respectively. The measurement agreement is within the range of results obtainable for conventional treatment machines. The low strength of the magnetic field does not affect dose measurements. Using the SWP to water correction factor, absolute doses for $ViewRay^{(R)}$ system can be measured.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.28-35
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• 2017

Recently, conventional hydraulic car lift systems face the technological limitations due to a lack of height control. The demand for height controllability is required in many tasks such as wheel alignment, and requires compensation for the structural deformation of the lift caused by irregular load distribution. In order to resolve this limitation of the conventional car lift, in this work, a new type of a hydraulic vehicle lift using a magneto-rheological (MR) valve system is proposed and analyzed. Firstly, the dynamic model of vehicle lift is formulated to evaluate control performance; subsequently, an MR valve is designed to obtain the desired pressure drop required in the car lift. Next, a proportional-integral-derivative (PID) controller is formulated to achieve accurate control of the lifting height and then computer simulations are undertaken to show accurate height control performances of the proposed new car lift system.

• Smart Media Journal
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• v.11 no.9
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• pp.81-93
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• 2022

In an era where non-face-to-face meetings become common, eXtended Reality(XR) is rapidly developing and filling areas that are not satisfied in online meetings based on existing photos/video method. In particular, general users are also able to easily access and use HMD-type mixed reality devices. However, the basic operations applied in HMD-type in Mixed Reality(MR) with hands as the main input tool do not have a standardized system, and each manufacturer operates in a separate response to each other's hand movements. Therefore, this study considered that a systematic hand motion matching system considering the usability and efficiency of operations performed in mixed reality was necessary, and conducted a study to clarify this. First, the basic operation performed in the MR environment and its attributes were investigated, and at the same time, the structure of the hand and the attributes of the possible hand movements were identified. Based on the identified properties, it is intended to present a system that can intuitively and efficiently match basic operation properties in the MR environment with subtle operation properties according to the structure/context of the hand.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.77-77
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• 2003

CT와 MRI의 단면 영상을 대상으로 영상분할 (Image segmentation)과 Image registration방법을 이용하여 인체 모델을 개발 하고자 한다. 우선 인체의 Head와 Neck부분의 CT와 MR 영상을 얻어 뼈, 근육, 인대, 그리고 그 밖의 장기의 해부학적 영상 특징을 분석하였다. 인체의 Head와 Neck 부분에 대한 CT와 MR 영상에 대해 각 부위별로 ROI(region-of-interrest)를 설정하였고, 각 volxel 마다 3차원 좌표를 계산할 수 있는 소프트웨어를 개발하였다. 특히 각 해부학적 영상에서 부위별로 CT 번호를 분석하고, pulse sequence에 따른 MRI 영상의 부위별 특정을 분석하였다. 이 분석한 자료를 바탕으로 영상 분할을 하였다. 영상 분할전에 각종 잡음(noise) 제거 및 영상 분할을 효과적으로 처리하기 위해 기본적인 영상처리 (filtering)를 구현하였고, 대조도(contrast) 및 밝기(brightness)를 조절할 수 있게 프로그램을 구현하였다. 영상 분할 방법 중 선(line) 및 에지(edge) 의 검출 방법, 문턱치화(threshold) 방법, 영역확대(region growing) 방법으로 영상 분할을 해봄으로써 우리의 인체 모델링 개발에 가장 적합한 영상 분할 알고리듬 방법을 찾도록 시도하였다. 결과적으로 말하면, 한가지 방법의 알고리듬을 쓰는 것보다는 인체의 부위에 따라 두 가지 이상의 알고리듬 방법을 쓰는 것이 원하고자 하는 부위를 영상 분할하는데 더 효과적이다는 것을 알게 되었다. 우리의 연구 과제에서는 영역확대(region growing) 방법과 문턱치화 방법, 모드법(피크니스, 밸리)의 알고리듬을 이용하여 영상 분할을 한 결과 우리가 얻고자 하는 인체 부위별 중 근육과 뼈를 구별하는데는 별 무리가 없었으나, 인대 및 기타 장기를 구별하는데는 어려움을 겪게 되었다. 이후에 좀더 알고리듬을 연구하여 이번 연구에서 구별하기 어려운 장기 부분도 구별 할 수 있도록 노력하겠다.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.4
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• pp.410-416
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• 2001

Objective: Disc displacement may affect the joint space narrowing between condylar head and glenoid fossa. This study was designed to evaluate the correlation between the joint space change and the severity of anterior disc displacement. Materials and Methods: Two hundreds temporomandibular joints MR images of TMD patients(170 joints) and asymptomatic volunteers(30 joints) were evaluated for this purpose. Anterior disc displacement was divided into 3 stages(normal, little to mild, and moderate to severe displacement) based on sagittal images, then joint spaces were measured at medial, central and lateral parts of condyle head on coronal MR images, respectively The joint spaces of 3 groups divided according to the severity of anterior disc displacement were compared. Results: The reduction of joint space was related to the severity of the anterior disc displacement at lateral, medial side and especially at center Conclusion: The temporomandibular joint space was affected by the severity of the anterior disc displacement.

• Investigative Magnetic Resonance Imaging
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• v.16 no.1
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• pp.55-66
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• 2012

Purpose : During brain MRI scanning, subject's head motion can adversely affect MRI images. To minimize MR image distortion by head movement, we developed an optical tracking system to detect the 3-D movement of subjects. Materials and Methods: The system consisted of 2 CCD cameras, two infrared illuminators, reflective sphere-type markers, and frame grabber with desktop PC. Using calibration which is the procedure to calculate intrinsic/extrinsic parameters of each camera and triangulation, the system was desiged to detect 3-D coordinates of subject's head movement. We evaluated the accuracy of 3-D position of reflective markers on both test board and the real MRI scans. Results: The stereo system computed the 3-D position of markers accurately for the test board and for the subject with glasses with attached optical reflective marker, required to make regular head motion during MRI scanning. This head motion tracking didn't affect the resulting MR images even in the environment varying magnetic gradient and several RF pulses. Conclusion: This system has an advantage to detect subject's head motion in real-time. Using the developed system, MRI operator is able to determine whether he/she should stop or intervene in MRI acquisition to prevent more image distortions.

• Journal of Ginseng Research
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• v.44 no.4
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• pp.563-569
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• 2020

Background: White ginseng consists of the roots and rhizomes of the Panax species, and red ginseng is made by steaming and drying white ginseng. While red ginseng has both polar and nonpolar ginsenosides, previous studies showed white ginseng to have only polar ginsenosides. Because nonpolar ginsenosides are formed through the manufacture of red ginseng from white ginseng, researchers have generally thought that nonpolar ginsenosides do not exist in white ginseng. Methods: We developed a simultaneous quantitative method for six nonpolar ginsenosides in white ginseng using reverse-phase high-performance liquid chromatography coupled with integrated pulsed amperometric detection. The nonpolar ginsenosides of white ginseng were extracted for 4 h under reflux with 50% methanol. Results: Using the gradient elution system, all target components were completely separated within 50 min. Nonpolar ginsenosides were determined in the rhizome head (RH), main root (MR), lateral root, and hairy root (HR) of 6-year-old white ginseng samples obtained from several regions (Geumsan, Punggi, and Kanghwa). The total content in the HR of white ginseng was 37.8-56.8% of that in the HR of red ginseng. The total content in the MR of white ginseng was 5.9-24.3% of that in the MR of red ginseng. In addition, the total content in the RH of white ginseng was 28.5-35.8% of that in the HR of red ginseng Conclusion: It was confirmed that nonpolar ginsenosides known to be specific components of red ginseng were present at substantial concentrations in the HR or RH of white ginseng.