• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.382-384
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• 2002

Filtered-Back-Projection technique is used in X-ray CT image reconstruction. This requires X-ray transmission data from all directions. As the transverse cross-section of the body is approximately 50 cm, transmitted X-rays in this direction are strongly attenuated. If X-ray transmission data in this direction is avoided, exposure to the patients seems to be reduced one 20th of usual value. Some alternative method has to be found for clinically sufficient image quality. New methods are under development and tentative results are reported that utilizes the principle of superposition.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.683-686
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• 2008

To diagnose vascular diseases from the viewpoint of hemodynamics, detailed quantitative hemodynamic information of related blood flows with a high spatial resolution of tens micrometer and a high temporal resolution in the order of millisecond were required. For investigating the hemodynamic phenomena of vascular circulatory diseases, a new diagnosing technique combining a medical radiography and PIV method was newly developed. This technique consisted of a medical X-ray tube, an X-ray CCD camera, a shutter module for double pulse-type X-ray source, and a synchronizer. Through several preliminary tests, the feasibility of the angiographic PIV technique was verified. For in-vivo measurements to real blood flows, we developed tracer microcapsules which were optimized to this system by encapsulating a contrast material of iodine with a matrix material of PVA (polyvinylpyrrolidone). In near future, the angiographic PIV technique would be useful for diagnosing hemodynamic phenomena of vascular diseases and for their early detection.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.305-310
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• 2004

The Hot Embossing Lithography(HEL) as a method for the fabrication of nanostructure with polymer is becoming increasingly important because of its simple process, low cost, high replication fidelity and relatively high throughput. In this study, we investigated the characteristics of hot embossing lithography as a nanoreplication technique. To grasp characteristics of nano patterning rheology by process parameters(embossing temperature, pressure and time), we have carried out various experiments by using the DVD(400nm pattern width) and Blu-ray nickel stamps(150nm pattern width). During the hot embossing process, we have observed the characteristics of the size effect. The quality of products made by hot embossing is affected by its cooling shrinkage. The demolding process at the glass transition temperature results in low quality because of the shrinkage of the polymer. Therefore, the quantification of the temperature condition is essential for the replication of high quality.

• Economic and Environmental Geology
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• v.25 no.1
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• pp.79-85
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• 1992

An Interpretation technique is presented to determine strike, dip, velocity and depth of 3-D planar layers from refraction or reflection traveltime curve. This interpretation technique determines the direction of emerging ray from the slope of the traveltime curve and traces the emerging ray to the refractor or reflector. The ray direction in the last layer is used to decide the normal vector to the refractor or reflector from whick its dip, strike and velocity are calculated. The vertical depth to the refractor or reflector is computed by using the intercept or zero-offset time and the ray direction in each layer. Some tests on the interpretation method are performed for the sysnthetic traveltimes generated in 3-D model layers and show that the paramerters of the model layers are accurately determined.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.917-919
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• 2017

본 연구에서는 X-ray 산란선 보정을 위한 신경망에서 학습기법의 세부 방법론을 고찰한다. 학습데이터의 생성 과정과 데이터의 표현 과정에서 X-ray 영상의 특성을 반영하여 다양한 방법을 제시하고 실험적으로 고찰하였다. 학습을 위한 계산량의 문제와 유효하지 않은 학습데이터로 인한 성능 저하를 개선하기 위하여 샘플링과정을 수행하고 로컬영역을 고려하는 학습데이터 생성방법을 제시하였다. 실제 동일 피사체에 대하여 그리드 장비를 사용한 영상과 비교한 실험 결과를 통하여 제안된 방법의 유용성을 평가하였다.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3153-3155
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• 1999

최근 수년간 의료영상분야는 국내외적으로 급격한 발전을 거듭하고 있다. 특히 자기공명영상장치 (Magnetic Resonance Imaging), X-ray CT(Computed Tomography)와 단층촬영장치는 인체내부를 비침습적(non-invasive)으로 영상화함으로써 해부학적인 질병진단에 많은 장점을 가지고 있다. 이와같은 단층영상 재구성에는 역매트릭스법(matrix inversion). 반복재구성법(interative method), 역투영 법(back-projection), 2차원 Fourier 변환법(2D FFT), 중첩재구성법(Filtered back-projection) 등의 다양한 알고리즘을 사용하고 있다. 본 연구에서는 X-ray CT에서의 단층영상재구성 기법 중 널리 사용되고 있는 Filtered Back Projection 기법의 연산순서도와 연산량을 분석하고 이를 시뮬레이션을 통하여 확인하고 실시간 영상재구성을 위하여 범용 Digital Signal Processor의 병렬처리시스템 구성에 기반된 최적 Architecture를 선정하고자 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.239-242
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• 2006

골다공증은 해면골의 골소주 두께 감소 및 파단에 기인한 전체적인 골질이 저하되는 질병이다. 골다공증을 예방과 조기진단을 하기 위해서는 골밀도를 측정하여야 한다. 보다 나은 이미지를 얻기 위해 Digital X-Ray로 골밀도를 측정하여 영상 처리하기 위한 방법을 제시한다. 먼저 디지털 센서에서 증감지와 렌즈간 거리가 가까워서 증감지의 중심과 주변부의 광 경로차이가 발생하므로 왜곡이 발생하는데 이를 균일화하여야 한다. 그리고 X-Ray장비의 조건에 따라 영상에 많은 차이를 보이므로 영상의 밝기를 보정하는 과정이 필수적이다.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.457-464
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• 2000

In this paper, we describe the results of various calculations performed for a design of the thickness gauges that use the gamma-ray backscattering method. The radiation source is assumed to be the $_{24}$1Am(60keV gamma-ray) and the detector is a single crystal scintillator in a cylindrical form. The source is located at the center of the detector with the collimator of a cylindrical shape. First, when gamma-rays are incident on a material with a constant angle, we compute the variations of the spectrum for the photons scattered into different angular intervals. Next, we compute for an optimal size for the collimator cylinder for a fixed detector size and an optimal distance from the detector to the material. Finally, we compute the number of observed photons for different thickness of two different materials, a plastic film and an Al foil.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.1181-1183
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• 2022

신생아 호흡곤란증후군(RDS, Respiratory Distress Syndrome)은 미숙아 사망의 주된 원인 중 하나이며, 이 질병은 빠른 진단과 치료가 필요하다. 소아의 x-ray 영상을 시각적으로 분석하여 RDS 의 판별을 하고 있으나, 이는 전문의의 주관적인 판단에 의지하기 때문에 상당한 시간적 비용과 인력이 소모된다. 이에 따라, 본 논문에서는 전문의의 진단을 보조하기 위해 심층 신경망을 활용한 소아 RDS/nonRDS 판별 방법을 제안한다. 소아 전신 X-ray 영상에 폐 영역 분할을 적용한 데이터 세트와 증강방법으로 추가한 데이터 세트를 구축하며, RDS 판별 성능을 높이기 위해 ImageNet 으로 사전학습된 DenseNet 판별 모델에 대해 구축된 데이터 세트로 추가 미세조정 학습을 수행한다. 추론 시 입력 X-ray 영상에 대해 MSRF-Net 으로 분할된 폐 영역을 얻고 이를 DenseNet 판별 모델에 적용하여 RDS 를 진단한다. 실험결과, 데이터 증강과 폐 영역을 분할을 적용한 판별 방법이 소아전신 X-ray 데이터 세트만을 사용하는 것과 비교하여 3.9%의 성능향상을 보였다.

• Nuclear Engineering and Technology
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• v.22 no.2
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• pp.101-107
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• 1990

The PIXE (Proton Induced X-ray Emission) method is applied to the quantitative analysis of trace elements in tap water, red wine, urine and old black powder samples. Sample irradiations are performed with a 1.202 MeV proton beam from the SNU 1.5-MV Tandem Van de Graaff accelerator, and measurements of X-ray spectra are made by the Si(Li) spectrometer To increase the sensitivity of analysis tap water is preconcentrated by evaporation method. As an internal standard, Ni powder is mixed with black powder sample and yttrium solution is added to the other samples. The analyses of the PIXE spectra are carried out by using the AXIL (Analytical X-ray Analysis by Iterative Least-squares) computer code, in which the routine for least-squares method is based on the Marquardt algorithm. The elements such as Mg, Al, Si, Ti, Fe and Zn are analyzed at sub-ppm levels in the tap water sample. In the red wine sample prepared without preconcentration. the element Ti is detected in the amount of 3ppm. In conclusion, the PIXE method is proved to be appropriate for the analysis of liquid samples by relative measurements using the internal standard. and is expected to be improved by the use of evaluated X-ray production cross-sections and the development of sample preparation techniques.