Brain CT에서 발생하는 선속경화현상 감소방안에 관한 연구

김현주(Kim, Hyun-Ju) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.12

연구는 Brain CT검사 시 영상에서 발생하는 선속경화현상의 원인과 감소방법을 알아보기 위하여 선속경화현상에 영향을 미치는 관전압, 관전류, 단면두께, 갠트리 각도, 기준선에 변화를 주었다. 사용한 장비로는 Somatom Sensation 16장비 로 Bone opaque head phantom을 이용 영상영향인자에 변화를 주어 스캔하였고 획득한 영상 데이터를 이용하여, CT값 분석을 이용한 정량적 분석과 CT영상평가표를 이용한 정성적 평가를 시행하였다. 정량적 분석결과 관전압은 140kVp일때 31.56±2.89HU로 측정되었고, 관전류의 경우 150mA에서 -3.87±0.12HU, 절편두께는 3mm에서 2.29±0.78HU로 측정되었으며 갠트리 각도에서 IOML이 13.31±1.03HU로 선속경화현상이 가장 적었다. 정성적 분석결과 대부분의 평가자들이 140kVp, 150mA, 3mm, IOML 또는 OML에서 스캔한 영상을 선속경화현상이 적게 발생한 영상으로 평가하였으며 모든 조건에서 변화 인자와 비교 시 통계학적으로 유의한 차이가 있었다.(P<0.05) 따라서, 임상적용 시 허용선량한도 범위 내에서 관전압은 높여 주고 관전류는 영상 화질 저하에 영향을 미치지 않는 범위 내에서 낮게 설정하며, 절편두께는 해상도 저하를 고려하여 얇은 절편두께를 사용하고, 갠트리 각도는 IOML 또는 OML을 이용한다면 선속경화현상에 의해 발생되어지는 인공물을 최소화시 켜 영상 판독자와 환자에게 보다 정확한 양질의 영상을 제공할 수 있을 것으로 사료된다. This study aim is occur in brain CT cause of beam hardening effect and reducing method, We will scan Bone opaque bead phantom on variation of image on the influence factor with equipment called ‘Samatom Senation 16’ with following listed herein : tube voltage, tube current, slice thickness, gantry angle, base line which affect beam-hardening effect. After that we are going to start Quantitative Analysis resulted in previous scanning and Qualitative Assessment with CT image sheet evaluation. result of quantitative analysis 140kVp 31.56±2.89HU on tube voltage, 150mA -3.87±0.12HU on tube current, 3mm on slice thickness, and 13.31±1.03HU IOML on gantry angle which was the least beam-hardening effect. Like Qualitative Analysis, we went through Qualitative Assessment and most of valuers got a result of 140kVp on tube voltage, 150mA on tube current, 3mm on slice thickness. As before valuers evaluated gantry angle that scanned image from IOML or OML was the least beam-hardening effect occured. There are meaningful differences when we compare all theses factors statistically(P<0.05). therefore We consider that Minimizing artifact that caused by beam-hardening effect can provide better quality of image to deciphers and patients. if we rise tube voltage in permissible dose limit, set tube current in a limit that does not effect to image quality, use slice thickness too thin enough to harm resolution, use IOML or OML on gantry angle.

On modeling coupling beams incorporating strain-hardening cement-based composites

Chung-Chan Hung,Yen-Fang Su 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.4

Existing numerical models for strain-hardening cement-based composites (SHCC) are short of providing sufficiently accurate solutions to the failure patterns of coupling beams of different designs. The objective of this study is to develop an effective model that is capable of simulating the nonlinear behavior of SHCC coupling beams subjected to cyclic loading. The beam model proposed in this study is a macro-scale plane stress model. The effects of cracks on the macro-scale behavior of SHCC coupling beams are smeared in an anisotropic model. In particular, the influence of the defined crack orientations on the simulation accuracy is explored. Extensive experimental data from coupling beams with different failure patterns are employed to evaluate the validity of the proposed SHCC coupling beam models. The results show that the use of the suggested shear stiffness retention factor for damaged SHCC coupling beams is able to effectively enhance the simulation accuracy, especially for shear-critical SHCC coupling beams. In addition, the definition of crack orientation for damaged coupling beams is found to be a critical factor influencing the simulation accuracy.

Computed tomographic beam-hardening artefacts: mathematical characterization and analysis

Park, Hyoung Suk,Chung, Yong Eun,Seo, Jin Keun Royal Society 2015 Philosophical transactions. Series A, Mathematical Vol.373 No.2043

<P>This paper presents a mathematical characterization and analysis of beam-hardening artefacts in X-ray computed tomography (CT). In the field of dental and medical radiography, metal artefact reduction in CT is becoming increasingly important as artificial prostheses and metallic implants become more widespread in ageing populations. Metal artefacts are mainly caused by the beam-hardening of polychromatic X-ray photon beams, which causes mismatch between the actual sinogram data and the data model being the Radon transform of the unknown attenuation distribution in the CT reconstruction algorithm. We investigate the beam-hardening factor through a mathematical analysis of the discrepancy between the data and the Radon transform of the attenuation distribution at a fixed energy level. Separation of cupping artefacts from beam-hardening artefacts allows causes and effects of streaking artefacts to be analysed. Various computer simulations and experiments are performed to support our mathematical analysis.</P>

Usefulness Evaluation of Application of Metallic Algorithm Reducing for Beam Hardening Artifact Occur in Typical Brain CT Image

Hyeon ju Kim(김현주) 한국방사선학회 2018 한국방사선학회 논문지 Vol.12 No.3

The study attempted to use computed tomography images to determine the usefulness of the reduction in the axial reduction algorithm in the event of a metallic artifacts reduction in the image of the beam-hardening effect, which is known as the most effective method of reducing metallic artifact reduction in the image and the reduction of the metal produced in this study. As a result, the result is increased to 140 kVp to reduce the value of the CT value by 0.02 to 0.05 %, resulting in decreased axial effect (P 〉 0.05). The CT value decreased from 12.4 to 26.9 % when applied to the reduction of the metallic. 12.4 to 26.9 % (p〈0.05). In addition, in the qualitative assessment by the clinical trial evaluation, it was assessed as 1.8 points after applying the MAR algorithm, In the resolution of resolution and contrast evaluations, the estimation of the decrease in metallic artifact effects was assessed as the metal was assessed to be scored 7.2 points after the MAR algorithm was evaluated. Therefore, in case of artifacts due to irreversible beam hardening effect, it is useful to reduce artifacts caused by beam hardening effect by using various methods derived from existing researches and scanning by applying the metal artifact reduction algorithm proposed in this experiment. 본 연구는 두부 인체모형 팬텀을 컴퓨터 단층촬영 장치를 이용하여 스캔 후 영상에서 발생한 선속경화 현상을 고관전압 적용 방법과 본 연구에서 적용한 금속인공물감소 알고리즘 적용 영상을 비교하여 금속 인공물감소 알고리즘 적용의 유용성을 알아보고자 하였다. 그 결과 관전압을 140 kVp로 높여 스캔 시 CT value가 0.02~0.05 % 감소하여 선속경화현상 감소 효과가 상대적으로 낮았으며(P〉0.05), 금속인공물감소 알고리즘 적용 시 CT value가 12.4~26.9 % 감소하여 선속경화현상 감소 효과에 상대적으로 의미가 있는 것으로 분석되었다(p〈0.05). 또한 임상영상평가표에 의한 정성적 평가에서도 인공물의 경우 MAR알고리즘 적용 후 1.8점으로 평가 되었고, 해상도 및 대조도 평가에서 MAR알고리즘 후 7.2점으로 평가되어 선속경 화현상 감소에 있어 금속인공물감소 알고리즘 적용이 의미가 있는 것으로 평가되었다. 따라서 불가항력적으로 발생하는 선속경화 현상에 의한 인공물의 경우 기존연구에서 도출한 다양한 방법과 더불어 본 실험을 통해 제시한 금속인공물 감소 알고리즘을 적용하여 스캔한다면 선속경화현상에 의해 발생한 인공물 감소에 유용할 것으로 사료된다.

머리 CT영상에서 흔히 발생하는 선속경화인공물 감소를 위한 금속인공물감소 알고리즘 적용의 유용성 평가

김현주 ( Hyeon Ju Kim ) 한국방사선학회 2018 한국방사선학회 논문지 Vol.12 No.3

본 연구는 두부 인체모형 팬텀을 컴퓨터 단층촬영 장치를 이용하여 스캔 후 영상에서 발생한 선속경화현상을 고 관전압 적용 방법과 본 연구에서 적용한 금속인공물감소 알고리즘 적용 영상을 비교하여 금속인공물감소 알고리즘 적용의 유용성을 알아보고자 하였다. 그 결과 관전압을 140 kVp로 높여 스캔 시 CT value가 0.02~0.05 % 감소하여 선속경화현상 감소 효과가 상대적으로 낮았으며(P>0.05), 금속인공물감소 알고리즘 적용 시 CT value가 12.4~26.9 % 감소하여 선속경화현상 감소 효과에 상대적으로 의미가 있는 것으로 분석되었다(p<0.05). 또한 임상영상평가표에 의한 정성적 평가에서도 인공물의 경우 MAR알고리즘 적용 후 1.8점으로 평가 되었고, 해상도 및 대조도 평가에서 MAR알고리즘 후 7.2점으로 평가되어 선속경화현상 감소에 있어 금속인공물감소 알고리즘 적용이 의미가 있는 것으로 평가되었다. 따라서 불가항력적으로 발생하는 선속경화 현상에 의한 인공물의 경우 기존연구에서 도출한 다양한 방법과 더불어 본 실험을 통해 제시한 금속인공물 감소 알고리즘을 적용하여 스캔한다면 선속경화현상에 의해 발생한 인공물 감소에 유용할 것으로 사료된다. The study attempted to use computed tomography images to determine the usefulness of the reduction in the axial reduction algorithm in the event of a metallic artifacts reduction in the image of the beam-hardening effect, which is known as the most effective method of reducing metallic artifact reduction in the image and the reduction of the metal produced in this study. As a result, the result is increased to 140 kVp to reduce the value of the CT value by 0.02 to 0.05 %, resulting in decreased axial effect (P > 0.05). The CT value decreased from 12.4 to 26.9 % when applied to the reduction of the metallic. 12.4 to 26.9 % (p<0.05). In addition, in the qualitative assessment by the clinical trial evaluation, it was assessed as 1.8 points after applying the MAR algorithm, In the resolution of resolution and contrast evaluations, the estimation of the decrease in metallic artifact effects was assessed as the metal was assessed to be scored 7.2 points after the MAR algorithm was evaluated. Therefore, in case of artifacts due to irreversible beam hardening effect, it is useful to reduce artifacts caused by beam hardening effect by using various methods derived from existing researches and scanning by applying the metal artifact reduction algorithm proposed in this experiment.

Capacity Magnification by Imposing Composite Action of Precast Concrete Flanged Girders

Hamdy M. Afefy,Nesreen M. Kassem,Salah El-Din F. Taher 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7

This paper presents an experimental study in order to verify the efficiency of different connecting techniques in improving thehorizontal shear resistance of composite concrete flanged beams. The studied composite beams consisted of precast concrete websinterconnected with precast concrete flanges. Different connecting techniques had been considered; namely, plain/reinforced Ultra-High-Performance Strain-Hardening Cementitious Composites (UHP-SHCC) shear pockets, UHP-SHCC shear buckets in the flangeaccommodated extended steel dowels from the web, unbonded internal steel fasteners and intermediate shear intrusions. Eightcomposite flanged beams incorporating different connecting techniques along with three reference beams; monolithic, successivelycast flanged beam and unconnected web/flange beams were prepared and tested up to failure under two cycles of non-reversalrepeated loading. Furthermore, the push-off test method was employed in order to determine the horizontal shear resistance of theused connecting techniques. Each technique came up with advantages and disadvantages. Therefore, it is a matter of compromise todecide the most appropriate technique according to the necessary criteria (ultimate capacity or ductility). Finally, the horizontal shearresistances were calculated based on the experimental findings and compared with the stipulated resistances in the ECP 203-2007and the ACI 318-14 design codes. It was found that the design codes’ values showed conservative results.

$CO_2$ 레이저 분산빔에 의한 표면경화가 구상흑연주철의 피로특성에 미치는 영향

박근웅,한유희,이상윤 한국레이저가공학회 1999 한국레이저가공학회지 Vol.2 No.2

This study has been performed to investigate into some effects of the output power and traverse speed of laser beam on the microstructures, hardness and fatigue resistance of the ductile iron surface-hardened by $CO_2$ laser defocussed beam. Optical micrographs have shown that with increasing the output power and decreasing the traverse speed, the martensite was coarsened and some retained austenite were appeared in ductile iron. The microstructures of hardening zone were composed of bull's eye and some nodular graphite dissolved structures by the effect of self quenching. Fatigue fracture characteristics of ductile iron have appeared in the high stress and low stress ranges. The fracture initiated at nodular graphites in the surface hardened layer due to the stress concentration caused by a notch effect. The interior graphite nodules were broken away or popped out during crack propagation. Fatigue test has shown that values of fatigue strength considerably increased with increasing output power at a given traverse speed.

Hybrid model-based and deep learning-based metal artifact reduction method in dental cone-beam computed tomography

허진,신영길,이호 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

Objective: To present a hybrid approach that incorporates a constrained beam-hardening estimator (CBHE) and deep learning (DL)-based post-refinement for metal artifact reduction in dental cone-beam computed tomography (CBCT). Methods: Constrained beam-hardening estimator (CBHE) is derived from a polychromatic X-ray attenuation model with respect to X-ray transmission length, which calculates associated parameters numerically. Deep-learning-based post-refinement with an artifact disentanglement network (ADN) is performed to mitigate the remaining dark shading regions around a metal. Artifact disentanglement network (ADN) supports an unsupervised learning approach, in which no paired CBCT images are required. The network consists of an encoder that separates artifacts and content and a decoder for the content. Additionally, ADN with data normalization replaces metal regions with values from bone or soft tissue regions. Finally, the metal regions obtained from the CBHE are blended into reconstructed images. The proposed approach is systematically assessed using a dental phantom with two types of metal objects for qualitative and quantitative comparisons. Results: The proposed hybrid scheme provides improved image quality in areas surrounding the metal while preserving native structures. Conclusion: This study may significantly improve the detection of areas of interest in many dentomaxillofacial applications.

CO₂ 레이저 분산빔에 의한 표면경화가 구상흑연주철에 피로특성에 미치는 영향

박근웅,이상윤,한유희 한국레이저가공학회 1999 한국레이저가공학회지 Vol.2 No.2

This study has been performed to investigate into some effects of the output power and traverse speed of laser beam on the microstructures, hardness and fatigue resistance of the ductile iron surface-hardened by CO₂ laser defocussed beam. Optical micrographs have shown that with increasing the output power and decreasing the traverse speed, the martensite was coarsened and some retained austenite were appeared in ductile iron. The microstructures of hardening zone were composed of bull's eye and some nodular graphite dissolved structures by the effect of self quenching. Fatigue fracture characteristics of ductile iron have appeared in the high stress and low stress ranges. The fracture initiated at nodular graphites in the surface hardened layer due to the stress concentration caused by a notch effect. The interior graphite nodules were broken away or popped out during crack propagation. Fatigue test has shown that values of fatigue strength considerably increased with increasing output power at a given traverse speed.

변형경화형 시멘트 복합체로 보-기둥 접합부가 보강된 전단항복형 철근콘크리트 보의 구조성능

장광수(Jang Gwang-Soo),송선화(Song Seon-Hwa),김윤수(Kim Yun-Su),김선우(Kim Sun-Woo),김용철(Kim Yong-Cheol),윤현도(Yun Hyun-Do) 대한건축학회 2008 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.28 No.1(구조계)

It has been shown that many reinforced concrete structures designed without seismic details have experienced brittle shear failures in the beam-column joint area and resulted in large permanent deformations and structural collapse. In this study, experimental investigations into the performance of exterior reinforced concrete beam-column joints strengthened with the strain-hardening cementitous composite(SHCC) reinforced under cyclic loading were presented. The properties of reinforcing fiber, as tensile strength, aspect ratio and elastic modulus, have great effect on the fracture behavior of SHCC. The research emphasis is on the mechanical properties of SHCC made in Polyvinyl alcohol(PVA), Polyethylene (PE), and how this affects the composite property, and ultimately its strain-hardening performance. Three beam-column joint specimens were tested to investigate behaviors of each specimen under cyclic load and to compare performances of seismic retrofit. According to the experimental study, the retrofit strengthened with the SHCC provides significant improvements of flexural capacity and ductility of beam-column joints originally built without seismic details.