• Investigative Magnetic Resonance Imaging
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• 제23권1호
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• pp.38-45
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• 2019

Purpose: To demonstrate the high-resolution numerical simulation of the respiration-induced dynamic $B_0$ shift in the head using generalized susceptibility voxel convolution (gSVC). Materials and Methods: Previous dynamic $B_0$ simulation research has been limited to low-resolution numerical models due to the large computational demands of conventional Fourier-based $B_0$ calculation methods. Here, we show that a recently-proposed gSVC method can simulate dynamic $B_0$ maps from a realistic breathing human body model with high spatiotemporal resolution in a time-efficient manner. For a human body model, we used the Extended Cardiac And Torso (XCAT) phantom originally developed for computed tomography. The spatial resolution (voxel size) was kept isotropic and varied from 1 to 10 mm. We calculated $B_0$ maps in the brain of the model at 10 equally spaced points in a respiration cycle and analyzed the spatial gradients of each of them. The results were compared with experimental measurements in the literature. Results: The simulation predicted a maximum temporal variation of the $B_0$ shift in the brain of about 7 Hz at 7T. The magnitudes of the respiration-induced $B_0$ gradient in the x (right/left), y (anterior/posterior), and z (head/feet) directions determined by volumetric linear fitting, were < 0.01 Hz/cm, 0.18 Hz/cm, and 0.26 Hz/cm, respectively. These compared favorably with previous reports. We found that simulation voxel sizes greater than 5 mm can produce unreliable results. Conclusion: We have presented an efficient simulation framework for respiration-induced $B_0$ variation in the head. The method can be used to predict $B_0$ shifts with high spatiotemporal resolution under different breathing conditions and aid in the design of dynamic $B_0$ compensation strategies.

• 한국병원경영학회지
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• 제21권3호
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• pp.37-52
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• 2016

The purpose of this study was to analyze the job of Head hospital coordinators based on the DACUM(Developing A Curriculum) method. The contents of this study were to extract the duties, tasks and performance standards consisting of the job of a Head hospital coordinator and to investigate levels of importance, difficulties, frequency and entry level on each task, and to make out a job model of Head hospital coordinators. A DACUM committee(seven members) was composed to analyze the job of Head hospital coordinators and the committee members were totally nine : a facilitator, seven Head hospital coordinators and a recorder. This study was conducted in Seoul and Gyeonggi Province from August to December, 2015. The major findings of this study were as follows; first, a Head hospital coordinator is defined to be an expert to create values and culture of a hospital, plan and manage hospital's efficient management methods to maximize customer satisfaction and improve the management of a hospital. Second, the job of Head hospital coordinators was categorized into total nine duties and sixty eight tasks. Third, duties in the job of Head hospital coordinators were classified into organization of medical management planning, medical management analysis, medical service quality management, hospital marketing, hospital customer management, hospital human resource management, hospital organization management, hospital financial management and self development.

• 한국전자파학회논문지
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• 제9권6호
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• pp.776-787
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• 1998

835 MHz에서 동작하는 셀룰라 휴대폰에 의한 인체 두부내의 1 g 및 10 g 평균 비홉수율(specific absorption rate, SAR)을 해석한다. 사용되는 수치방법은 총 전자기장 유한차분 시간영역(finite-difference time-domain, FDTD) 기법이다. 전화기는 도체박스, 플라스틱 케이스 그리고 모노폴 안테나와 나선형 안테나 로 구성된 whip 안테나로 모의되었다. 공간 정밀도 3 mm의 이산적 인체두부 모델은 MRI(Magnetic Resonance Imaging), CT(computerized tomography) 그리고 해부학적 이미지에 기초한 것이다 안테나를 뽑은 전화기와 접은 전화기에 대한 근역장 및 원역장 복사 패턴이 분석되었다. SAR 평가를 위한 재현성 있는 기법을 제공하기 위해 조직내의 1 g 또는 10 g의 질량을 갖는 체적을 취하는 두 가지 방법을 제안하고 비교 한다.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.193-200
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• 2002

Simple spring-damper-mass models have been widely used to investigate whole-body vortical biodynamic response characteristics of the seated vehicle driver. Most previous models have not considered the effect of wobbling masses; i.e. heart, lungs, liver, intestine, etc. In this study, 4 -DOF seated driver model including one non-rigid mass representing wobbling visceral mass, 5-DOF model including intestine, and 10-DOF model including five lumbar vertebral masses were proposed. The model parameters were identified by a combinatorial optimization technique. simulated annealing method. The objective function was chosen as the sum of error between model response of seat-to-head transmissibility and driving point mechanical impedance and those of experimental data for subjects seated erect without backrest support. The model response showed a good agreement with the experimental response characteristics. Using a 10-DOF model, calculated resonance frequency of lumbar spine at 4Hz was matched well with experimental results of Panjabi et al.

• 한국산업보건학회지
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• 제7권1호
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• pp.87-98
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• 1997

In this study, subway train vibration has been measured to characterize the whole body vibration of Seoul subway lines for various human postures. Results show that the floor vibration level of the subway trains in the vertical direction is higher than that in other directions. At the standing human posture, vibration level of the head in the right-left direction are increased while that in the vertical direction is decreased. It is assumed that the different flexibility of the human body and the rolling motion of the subway trains are the main cause. At the sitting posture with back seat on, vibration level in the right and left direction at the human ischial tuberosities is lower than that in other directions. Results also show that there were little difference between back-seat on model and back-seat off model. Transmissibility analysis shows how the subway vibration affects the response of a human body.

• Asian Pacific Journal of Cancer Prevention
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• 제13권3호
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• pp.891-896
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• 2012

This study focused on infection rates and subtypes of human papillomavirus (HPV) in patients with oropharyngeal squamous cell carcinoma (OSCC), and the relationship between HPV status and prognosis of the disease. We evaluated sixty-six OSCC patients who met the enrollment criteria during the period from January 1999 to December 2009. The presence or absence of oncogenic HPV types in tumors was determined using the SPF10 LiPA25 assay. Overall survival (OS) and disease specific survival (DSS) for HPV positive and HPV negative patients were estimated using Kaplan-Meier analysis. The Cox regression model was applied for multivariate analysis. HPV-DNA was detected in 11(16.7%) of all specimens. Among them, 7 were type HPV-16, while other types were HPV-16/11, HPV-35, HPV-58/52, and HPV-33/52/54. Patients with HPV positive tumors were more likely to be female, non-smokers and non-drinkers (p=0.002, 0.001 and 0.001, respectively). After a median follow-up of 24.5 months, patients with HPV positive tumors had significantly better overall survival (HR=0.106[95%CI=0.014-0.787], p=0.016,) and disease specific survival (HR=0.121[95%CI=0.016-0.906], p=0.030). Patients with HPV positive OSCC have significantly better prognosis than patients with HPV negative tumors. HPV infection is an independent prognostic factor.

• 자동차안전학회지
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• 제4권2호
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• pp.37-43
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• 2012

The purpose of this research is to obtain and analyze dynamic responses from human volunteers for the development of the human-like mechanical or mathematical model for Korean males in automotive rear collisions. This paper focused on the introduction to a low-speed rear impact sled test involving Korean male subjects, and the accumulation of the motion of head and neck. A total of 50 dynamic rear impact sled tests were performed with 50 human volunteers, who are 30-50 year-old males. Each subject can be involved in only one case to prevent any injury in which he was exposed to the impulse that was equivalent to a low-speed rear-end collision of cars at 5-8 km/h for change of velocity, so called, ${\Delta}V$. All subjects were examined by an orthopedist to qualify for the test through the medical check-up of their necks and low backs prior to the test. The impact device is the pendulum type, tuned to simulate the crash pulse of a real vehicle. All motions and impulses were captured and measured by motion capture systems and pressure sensors on the seat. Dynamic responses of head and T1 were analyzed in two cases(5 km/h, 8 km/h) to compare with the results in the previous studies. After the experiments, human subjects were examined to check up any change in the post medical analysis. As a result, there was no change in MRI and no injury reported. Six subjects experienced a minor stiffness on their back for no more than 2 days and got back to normal without any medical treatment.

• 인터넷정보학회논문지
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• 제9권3호
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• pp.91-101
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• 2008

본 논문에서는 구성요소와 그들 간의 유연한 연결을 가진 인체 모델로 인체를 추적하기 위한 구성요소 기반 확률 전파를 제안한다. 인체는 사람의 동작을 추적하는데 필요한 6개의 인체 부위로 나뉘는데, 머리, 몸통, 왼팔, 오른팔, 왼발, 오른발 등이다. 제안하는 추적 방법은 인체 전체의 실루엣을 추적하지 않는 것이 아니라 구성요소로 이루어진 인체모델을 이용하여 인체의 각 부위를 개별적으로 추적하게 된다. 제안된 인체 추적 시스템은 유아의 동작 교육에 적용되는데, 균형잡기, 앙감질, 뛰기, 걷기, 회전하기, 구부리기, 뻗기와 같은 동작을 추적하는데 이용된다. 제안하는 시스템은 인체 모델의 각 부위를 개별적으로 탐지하고 움직임을 추적하여 평균 97%의 추적율을 획득하였다.

• 한국광학회지
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• 제12권6호
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• pp.512-518
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• 2001

본 논문에서는 Head Mounted Display(HMD)용 광학계의 기하학적인 특징과 회절광학소자를 이용한 HMD용 광학계 설계의 개념에 대해 논의하였다. 사용자가 영상을 볼 때 편안함을 갖도록 HMD용 광학계는 경량화, 소형화 및 고해상도를 만족해야 한다. 이러한 요구조건들을 만족시키기 위해 본 논문에서는 회절광학소자와 양면 비구면화를 적용하여 색수차와 단색수차를 보정하였다. 또한 인간의 눈을 모델링하여 일반화한 모형안을 HMD용 광학계의 설계 및 성능평가에 적용하였다.

• 한국방사선학회논문지
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• 제11권5호
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• pp.361-370
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• 2017

Brain MRI 검사에서는 영상을 얻기 위해 RF Pulse를 인체에 조사하게 되는데 이때 조사된 RF Pulse 에너지의 상당 부분은 우리 몸에 그대로 흡수되게 되고 이로 인해 인체 온도가 상승하게 되는데 노출 정도에 따라 인체에 영향을 주게 된다. 이러한 RF Pulse 에너지는 MRI 장비의 발전으로 인해 자기장의 세기가 1.5 Tesla에서 3 Tesla, 3 Tesla에서 7 Tesla로 높아지는 시점에서 자기장의 세기 변화에 따른 두부 전체의 SAR와 온도의 변화를 알아보고 위의 결과가 치아 임플란트 사용 여부에 따른 결과의 차이를 알아보기 위해 연구를 시작하게 되었다. 실험은 인체 두부 모델에 1.5 Tesla MRI 장비에서 발생되는 64 MHz RF Pulse 주파수, 3.0 Tesla MRI 장비에서 발생되는 128 MHz RF Pulse 주파수, 7 Tesla MRI 장비에서 발생되는 298 MHz RF Pulse 주파수를 조사하고 위의 실험을 치아 임플란트를 사용하였을 때와 사용하지 않았을 때로 나누어 XFDTD 프로그램을 사용하여 머리 주변의 SAR와 체온의 변화를 각각 실험하였다. 치아 임플란트를 하지 않았을 때보다 치아 임플란트를 하였을 때 SAR값은 7T의 RF Pulse 주파수 256MHz에서 최대 약 5800배의 차이를 나타냈으며 주파수가 증가할수록 치아 임플란트 사용으로 인한 SAR값의 차이는 크게 나타났다. 치아 임플란트를 하지 않았을 때보다 치아 임플란트를 하였을 때 두부전체의 온도변화는 2배에서 최대 4배 가까운 온도 상승을 나타내었다. 또한 RF Pulse 주파수가 증가할수록 SAR값은 증가하지만, 두부 전체의 온도는 감소하였는데 이는 주파수가 증가할수록 파장이 작을수록 인체표면에 흡수되는 양이 많아지기 때문이다. 향후 치아 임플란트 유무와 RF Pulse 주파수의 세기 변화로 인한 이상 반응 요인에 대한 연구를 통해 인체의 생리적 연구와 생화학적 연구 등 인체에 대한 영향과 관련하여 연구가 필요하다고 하겠다.