• 제목/요약/키워드: phantom model

검색결과 246건 처리시간 0.025초

An Optimized Mass-spring Model with Shape Restoration Ability Based on Volume Conservation

  • Zhang, Xiaorui;Wu, Hailun;Sun, Wei;Yuan, Chengsheng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제14권4호
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    • pp.1738-1756
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    • 2020
  • To improve the accuracy and realism of the virtual surgical simulation system, this paper proposes an optimized mass-spring model with shape restoration ability based on volume conservation to simulate soft tissue deformation. The proposed method constructs a soft tissue surface model that adopts a new flexion spring for resisting bending and incorporates it into the mass-spring model (MSM) to restore the original shape. Then, we employ the particle swarm optimization algorithm to achieve the optimal solution of the model parameters. Besides, the volume conservation constraint is applied to the position-based dynamics (PBD) approach to maintain the volume of the deformable object for constructing the soft tissue volumetric model base on tetrahedrons. Finally, we built a simulation system on the PHANTOM OMNI force tactile interaction device to realize the deformation simulation of the virtual liver. Experimental results show that the proposed model has a good shape restoration ability and incompressibility, which can enhance the deformation accuracy and interactive realism.

Precise System Models using Crystal Penetration Error Compensation for Iterative Image Reconstruction of Preclinical Quad-Head PET

  • Lee, Sooyoung;Bae, Seungbin;Lee, Hakjae;Kim, Kwangdon;Lee, Kisung;Kim, Kyeong-Min;Bae, Jaekeon
    • Journal of the Korean Physical Society
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    • 제73권11호
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    • pp.1764-1773
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    • 2018
  • A-PET is a quad-head PET scanner developed for use in small-animal imaging. The dimensions of its volumetric field of view (FOV) are $46.1{\times}46.1{\times}46.1mm^3$ and the gap between the detector modules has been minimized in order to provide a highly sensitive system. However, such a small FOV together with the quad-head geometry causes image quality degradation. The main factor related to image degradation for the quad-head PET is the mispositioning of events caused by the penetration effect in the detector. In this paper, we propose a precise method for modelling the system at the high spatial resolution of the A-PET using a LOR (line of response) based ML-EM (maximum likelihood expectation maximization) that allows for penetration effects. The proposed system model provides the detection probability of every possible ray-path via crystal sampling methods. For the ray-path sampling, the sub-LORs are defined by connecting the sampling points of the crystal pair. We incorporate the detection probability of each sub-LOR into the model by calculating the penetration effect. For comparison, we used a standard LOR-based model and a Monte Carlo-based modeling approach, and evaluated the reconstructed images using both the National Electrical Manufacturers Association NU 4-2008 standards and the Geant4 Application for Tomographic Emission simulation toolkit (GATE). An average full width at half maximum (FWHM) at different locations of 1.77 mm and 1.79 mm are obtained using the proposed system model and standard LOR system model, which does not include penetration effects, respectively. The standard deviation of the uniform region in the NEMA image quality phantom is 2.14% for the proposed method and 14.3% for the LOR system model, indicating that the proposed model out-performs the standard LOR-based model.

경직장초음파를 이용한 전립선 볼륨측정 시의 위치 연구: 전립선모형 제작과 실험 (Location Studies of Prostate Volume Measurement by using Transrectal Ultrasonography: Experimental Study by Self-Produced Prostate Phantom)

  • 김연민;윤준;변일균;이후민;김형균
    • 대한방사선기술학회지:방사선기술과학
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    • 제38권4호
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    • pp.437-442
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    • 2015
  • 전립선의 정확한 볼륨측정은 전립선암과 전립선비대의 진단, 치료 결정 및 예후 판정에 있어서 중요한 역할을 한다. 또한, 전립선암 선별검사에 사용하고 있는 혈청전립선특이항원(serum prostate-specific antigen)은 전립선의 볼륨과 서로 높은 상관관계를 보이기 때문에 이를 평가하기 위해서는 정확한 볼륨을 아는 것이 중요하다. 기존의 전립선 측정법이 다양하게 제시되고 있으나 전립선 모형 별 측정법에 대한 연구는 없었다. 본 연구에서는 다양한 모형의 팬텀을 제작하고 초음파를 이용하여 볼륨을 알아본 후 모형 별 측정위치를 찾아 새로운 측정방법을 제시하고자 한다. 초음파 검사를 통해 특징적인 전립선 모양 6개를 선정하였다. 이를 횡단과 종단영상을 참고하여 전립선 모형 6개를 제작하였다. 최적의 측정위치에서 각각 3회씩 반복측정 후 실제볼륨과 측정볼륨간의 유의성을 알아보기 위하여 Wilcoxon 부호순위 검정을 실시하였다. p값은 0.05이하일 때 유의한 것으로 정하였다. Axial 영상에서 돌출부위를 제외하고 안쪽으로 두고, Longitudinal 영상에서는 base와 apex의 오목한 부분에 측정 점을 놓았을 때 실제 전립선 크기와 일치도가 높았다. 실제볼륨과 측정볼륨간의 유의성은 p값 0.156으로 통계적으로 유의한 차이가 없었다. 전립선 axial 영상에서 전립선 이행대의 돌출이 심할 경우 돌출부위를 배제하고 측정하는 것이 실제 볼륨에 가까웠다. 또한 longitudinal영상에서는 apex부분이 가늘고 길어질 경우에 끝부분이 아닌 안쪽으로 측정 점을 잡아 그 점을 기준으로 타원을 그려 볼륨을 측정하는 것이 실제 볼륨에 가장 가까웠다.

모델식의 2차 근사에 의한 정량적인 초음파 단층 촬영 알고리즘 (A Quantitative Ultrasound Tomography Algorithm Via the Second Order Approximation of the Model Equation)

  • 김환우;김영길
    • 전자공학회논문지B
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    • 제29B권11호
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    • pp.16-21
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    • 1992
  • The validity of the application of the second-order Born equation to the ultrasound tomography algorithm is studied by comparing the scattered fields computed using the first-order Born equation, the first-order Rytove equation, and the second-order Born equation. The second-order Born equation turns out to provide more desirable results than the other two equations for a certain group of test objects. Phantom images with resolutions upto 1 pixel$\times$1 pixel are satisfactorily reconstructed using the second-order Born equation. It is shown that when the view angle is limited, good resonstruction results are also obtained using multi-frequency incident fields.

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ESTIMATION OF LOCAL LIQUID FILM THICKNESS IN TWO-PHASE ANNULAR FLOW

  • Lee, Bo-An;Yun, Byong-Jo;Kim, Kyung-Youn;Kim, Sin
    • Nuclear Engineering and Technology
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    • 제44권1호
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    • pp.71-78
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    • 2012
  • In many semi-empirical analyses of flow boiling heat transfer, an annular flow is often assumed as a model flow and the local liquid film thickness is a key parameter in the analysis. This work considers a simple electrical conductance technique to estimate the local liquid film thickness in two-phase annular flows. In this approach, many electrodes are mounted flush with the inner wall of the pipe. Voltage differences between two neighboring electrodes for concentric annular flows with various liquid film thicknesses are obtained before the main experiments and logged in a look-up table. For an actual application in the annual flow, voltage differences of neighboring electrodes are measured and then corresponding local film thicknesses are determined by the interpolation of the look-up table. Even though the proposed technique is quite simple and straightforward, the numerical and static phantom experiments support its usefulness.

Damage prediction of RC containment shell under impact and blast loading

  • Pandey, A.K.
    • Structural Engineering and Mechanics
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    • 제36권6호
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    • pp.729-744
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    • 2010
  • There is world wide concern for safety of nuclear power installations after the terrorist attack on World Trade Center in 2001 and several other civilian structures in the last decade. The nuclear containment structure in many countries is a double shell structure (outer shell a RCC and inner a prestressed concrete). The outer reinforced concrete shell protects the inner shell and is designed for external loading like impact and blast. A comparative study of non-linear response of reinforced concrete nuclear containment cylindrical shell subjected to impact of an aircraft (Phantom) and explosion of different amounts of blast charges have been presented here. A material model which takes into account the strain rate sensitivity in dynamic loading situations, plastic and visco-plastic behavior in three dimensional stress state and cracking in tension has been developed earlier and implemented into a finite element code which has been validated with published literature. The analysis has been made using the developed software. Significant conclusions have been drawn for dissimilarity in response (deflections, stresses, cracks etc.) of the shell for impact and blast loading.

Automated 2D/3D Image Matching Technique with Dual X-ray Images for Estimation of 3D In Vivo Knee Kinematics

  • Kim, Yoon-Hyuk;Phong, Le Dinh;Kim, Kyung-Soo;Kim, Tae-Seong
    • 대한의용생체공학회:의공학회지
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    • 제29권6호
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    • pp.431-435
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    • 2008
  • Quantitative information of a three dimensional(3D) kinematics of joint is very useful in knee joint surgery, understanding how knee kinematics related to joint injury, impairment, surgical treatment, and rehabilitation. In this paper, an automated 2D/3D image matching technique was developed to estimate the 3D in vivo knee kinematics using dual X-ray images. First, a 3D geometric model of the knee was reconstructed from CT scan data. The 3D in vivo position and orientation of femoral and tibial components of the knee joint could be estimated by minimizing the pixel by pixel difference between the projection images from the developed 3D model and the given X-ray images. The accuracy of the developed technique was validated by an experiment with a cubic phantom. The present 2D/3D image matching technique for the estimation of in vivo joint kinematics could be useful for pre-operative planning as well as post-operative evaluation of knee surgery.

주관적 촉감 재현을 위한 Haptic System의 Stiffness Model에 관한 연구 (Research on presentation of subjective tactile sensation by stiffness model of haptic system)

  • 이윤정;황민철;현혜정;김영주;김종화;박준석
    • 한국HCI학회:학술대회논문집
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    • 한국HCI학회 2007년도 학술대회 1부
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    • pp.863-868
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    • 2007
  • 본 연구는 Haptic System의 물리적 stiffness(N/mm)와 사용자의 주관적 촉감정보(단단하다, 무르다)의 상관성에 관한 것이다. tangible media와 같은 컨텐츠의 촉감을 실감나게 표현하기 위해서는 사용자가 주관적으로 느끼는 힘의 강도가 haptic system에 매핑이 되어야 한다. 따라서 사용자의 주관적인 힘의 강도와 haptic system의 물리적 stiffness간에 상관성 연구가 필요하다. 본 연구에서는 물리적 특성을 결정하고 하드웨어와 소프트웨어를 연동시켜 촉감을 모델링하는 haptic 렌더링을 통해 정량화된 외부의 자극(변화)에 대해 사람이 심리적으로 느끼고 있는 감각을 정량화하여 입력 자극과의 관계를 밝히고자 팬텀을 이용해 두 번의 실험을 실시하였다. 먼저 haptic system에서 사용자가 힘의 차이를 느낄 수 있는 stiffness의 해상도를 측정하고, 그에 따라 나뉘어진 해상도 별로 촉감에 대한 주관적인 평가를 하였다. ANOVA결과에 따르면 haptic system의 물리적 stiffness와 사용자의 주관적 촉감정보간에 유의한 상관관계가 분석되었으며 회귀분석을 실시하여 유의한 정도를 회귀 방정식으로 도출하였다. 따라서tangible media를 이용한 실감적인 촉감 컨텐츠를 재현하는 기술에 본 연구결과가 유용하게 사용되리라 기대된다.

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실험계획 법에 의한 혈중 글루코즈 측정 시 타 성분의 영향 분석 (Influence of Other Blood Components in Predicting Glucose Concentration using Design of Experiment)

  • 김연주;윤길원;전계진
    • 대한의용생체공학회:의공학회지
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    • 제22권6호
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    • pp.497-502
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    • 2001
  • 혈액 속의 글루코즈 농도를 측정 시 타 성분이 미치는 영향을 분석하였다. 이를 위하여 헤모글로빈을 포함한 총 5 가지의 주요 성분을 이용하여 혈액 팬텀을 만들었으며 글루코즈의 배음대역을 포함하는 1500 ~ 1850nm의 흡수스펙트럼을 측정하여 농도 추정 모델을 세웠다. 농도 예측은 다변량통계분석 모델인 부분최소자승회귀분석을 이용하였다 다른 성분들이 글루코즈 측정에 있어 미치는 영향은 실험계획법을 적용한 인자 분석에 의하여 조사하였다. 트리 글라이세라이드는 영향을 미치지 않는 것으로 나타났으며. 알부민과 글로불린의 경우 적은 범위의 영향을 주는 것으로 나타났다 하지만 헤모글로빈의 영향은 큰 것으로 나타나 글루코즈 측정에 있어 헤모글로빈의 농도 보상이 필요한 것으로 판명되었다.

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확장된 쐐기조사야에 의한 조직산란계수의 변화 (The Variation of PSF Induced Enlarged Wedged Fields)

  • 이정우;조화섭;박성렬
    • 대한방사선치료학회지
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    • 제10권1호
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    • pp.97-101
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    • 1998
  • In recent days, although many kinds of beam modifiers are developing and using for clinical purposes in accordance with progressing medical engineering, physical wedges are preferred to use as a beam modifier by a lot of institutions until now because of cost, complexities of dosimetry and mechanical uncertainties. According to progressing technology, available field size of wedge is more enlarger than that of old model LINAC. Because field size dependence of wedged fields increases in new model LINAC, we was trying to know that how much different PSFs are in enlarged wedged fields compared with open fields. In small or middle size of fields($4{\times}4{\sim}15{\times}15cm$), there are only a few percents of PSF variation between open and wedged fields. But there are $2{\sim}8\%\;variations\;in\;relatively\;large\;fields(20{\times}20{\sim}30{\times}40cm)$.

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