• 제목/요약/키워드: 산란감쇠

검색결과 118건 처리시간 0.031초

Effect of $180^{\circ}$ Reconstruction in Myocardium SPECT($^{99m}Tc$-Tetrofosmin) ($^{99m}Tc$-테트로포스민를 이용한 심근 SPECT 영상 재구성에서 $180^{\circ}$의 유용성)

  • Choi Sung Wook;Ji Yong Ki;Park Hoon;Kim KE;Suk Jae Dong
    • Journal of The Korean Radiological Technologist Association
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    • 제29권1호
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    • pp.67-71
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    • 2003
  • Purpose : 201Tl Myocardium SPECT Test uses $180^{\circ}$ reorganization due to the energy diffusion decrease by backbone and muscles, but $^{99m}Tc$-Tetrofosmin Myocardium SPECT Test can get more information by $360^{\circ}$

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Ultrasonic Scatter and Compensation of Interfacial Crack due to Thickness Variation of Dissimilar Bonded Components (이종 접합부재의 두께 변화에 따른 계면균열의 초음파 산란 보정)

  • Park, Sung-Il;Chung, Nam-Yong;Jin, Yoon-Ho
    • Proceedings of the KSME Conference
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.25-30
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    • 2004
  • In this paper, the compensation of interfacial scatter due to adhesive layer and adherend thickness ratio variation was applied to improve measuring precision by calculating ultrasonic attenuation coefficient in the Al/Epoxy dissimilar bonded components. The optimum condition of theoretical value and experimental measuring accuracy by the ultrasonic method in the Al/Epoxy dissimilar bonded components have been investigated. From the experimental results, we proposed a measurement method of the interfacial crack lengths by the ultrasonic attenuation coefficient and discussed it.

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A study on the effectiveness to satellite communications due to Asian Dust (황사에 의하여 위성통신에 미치는 영향분석)

  • 홍완표;김학섭;전영신
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 한국해양정보통신학회 2004년도 춘계종합학술대회
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    • pp.55-58
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    • 2004
  • To analysis on the degradation of the satellite communication signal due to Asian dust that was appeared on Korean peninsula during March and April 2004, EIRPs of L, S, C, Ku and Ka frequency band of the downlink of satellite communication link were measured by Satellite Signal Monitoring Center located in lcheon, Korea. The measured results were compared to the measurement values of PM10 and OPC that were measured by the Korea Meteorological Administration.

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Spray Distribution Measurement at High Ambient Pressure (고압 환경 하에서의 분무 분포 측정)

  • Cho, Seong-Ho;Im, Ji-Hyuk;Yoon, Young-Bin;Choi, Seong-Man;Han, Young-Min
    • Journal of the Korean Society of Visualization
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    • 제6권1호
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    • pp.59-65
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    • 2008
  • Distribution of spray was measured. Optical Line Patternator (OLP) was used to measure the planar distribution of the spray from a swirl-coaxial type injector. Ambient pressure was varied and injection pressure was fixed in experiment. As ambient pressure increased, spray distribution was changed from hallow cone to solid cone shape, and spray angle was decreased. Limitation in measuring dense spray was found at high ambient pressure condition.

A Study on the Region based Transmission Estimation and Refinement for haze removal (안개 제거를 위한 영역별 전달량 계산과 정련 방법에 관한 연구)

  • Kim, Sang-Kyoon;Xiang, Xiang;Park, Soon-Young;Park, Jong-Hyun;Cho, Wan-Hyun
    • Proceedings of the Korea Information Processing Society Conference
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    • 한국정보처리학회 2012년도 추계학술발표대회
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    • pp.543-544
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    • 2012
  • 객체 추적 및 모니터링 시스템에서 안개와 같은 환경적 불완전 요소는 비전 처리 성능에 많은 영향을 준다. 특히 안개는 빛의 산란과 흡수에 의한 감쇠로 탐지 영역내의 물체의 색상이 비슷해지고 채도가 매우 떨어지게 되어 객체의 형태를 구별하기 어려워진다. 따라서 실외에서 신뢰할 수 있는 비전 처리를 위해서는 안개와 같은 환경적 불완전 요소의 제거가 필수라 할 수 있다.

The Dose Characteristics of Designed Ir-192 Micro-source for Brachytherapy (근접조사용 Ir-192 마이크로선원의 디자인과 선량 특성)

  • 최태진;김진희
    • Progress in Medical Physics
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    • 제14권2호
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    • pp.81-89
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    • 2003
  • The dose distributions of designed Ir-192 micro-source were investigated by dose computations which were accomplished by employing shape of encapsule material and thickness of the source for self-absorption. The computation dose derived from air-kerma rate (S$_{k}$ ) and dose rate constant (Λ) includes the anisotropy of dose distribution around the source. We got the dose rate constants in a water medium is 1.154 cGy h$^{-1}$ U$^{-1}$ . The size of the source was 0.5 mm in diameter and 3.5 mm in length and it was encapsuled in 1.1 mm$\Phi$${\times}$5.5 mm of stainless steel sealed with 0.3 mm of filter thickness. The tissue dose of reference point at 1.0 cm radial distance of the source axis was delivered 1.154 Uh$^{-1}$ (1.3167${\times}$10$^{-3}$ cGy/mCi-sec) from the S$_{k}$ 4.108U/mCi of Ir-192 source. The filtration effect contributed to air-kerma strength as exponential filtering effect of 86.2% in total attenuation, but self-absorption was 88.4% from radial dose distributions. In particular, the dose attenuations showed a rapid anisotropic distributions as 56% of reference dose along to $\pm$10 degrees from the tip of source axis and 50% for of that to source-cable direction. We persist in use the large diameter of applicator will avoid the dose anisotropy by the filtered attenuation effects along the axis of Ir-192 micro-source.

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Effect of Attenuation Correction, Scatter Correction and Resolution Recovery on Diagnostic Performance of Quantitative Myocardial SPECT for Coronary Artery Disease (감쇠보정, 산란보정 및 해상도복원이 정량적 심근 SPECT의 관상동맥질환 진단성능에 미치는 효과)

  • Hwang, Kyung-Hoon;Lee, Dong-Soo;Paeng, Jin-Chul;Lee, Myoung-Mook;Chung, June-Key;Lee, Myung-Chul
    • The Korean Journal of Nuclear Medicine
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    • 제36권5호
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    • pp.288-297
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    • 2002
  • Purpose: Soft tissue attenuation and scattering are major methodological limitations of myocardial perfusion SPECT. To overcome these limitations, algorithms for attenuation, scatter correction and resolution recovery (ASCRR) is being developed, while quantitative myocardial SPECT has also become available. In this study, we investigated the efficacy of an ASCRR-corrected quantitative myocardial SPECT method for the diagnosis of coronary artery disease (CAD). Materials and Methods: Seventy-five patients (M:F=51:24, $61.0{\pm}8.9$ years old) suspected of CAD who underwent coronary angiography (CAG) within $7{\pm}12$ days of SPECT(Group-I) and 20 subjects (M:F=10:10, age $40.6{\pm}9.4$) with a low likelihood of coronary artery disease (Group-II) were enrolled. Tl-201 rest/ dipyridamole-stress Tc-99m-MIBI gated myocardial SPECT was performed. ASCRR correction was peformed using a Gd-153 line source and automatic software (Vantage-Pro; ADAC Labs, USA). Using a 20-segment model, segmental perfusion was automatically quantified on both the ASCRR-corrected and uncorrected images using an automatic quantifying software (AutoQUANT; ADAC Labs.). Using these quantified values, CAD was diagnosed in each of the 3 coronary arterial territories. The diagnostic performance of ASCRR-corrected SPECT was compared with that of non-corrected SPECT. Results: Among the 75 patients of Group-I, 9 patients had normal CAG while the remaining 66 patients had 155 arterial lesions; 61 left anterior descending (LAD), 48 left circumflex (LCX) and 46 right coronary (RCA) arterial lesions. For the LAD and LCX lesions, there was no significant difference in diagnostic performance. In Group-II patients, the overall normalcy rate improved but this improvement was not statistically significant (p=0.07). However, for RCA lesions, specificity improved significantly but sensitivity worsened significantly with ASCRR correction (both p<0.05). Overall accuracy was the same. Conclusion: The ASCRR correction did not improve diagnostic performance significantly although the diagnostic specificity for RCA lesions improved on quantitative myocardial SPECT. The clinical application of the ASC-RR correction requires more discretion regarding cost and efficacy.

Multi-layered Gap Measurement on In-Vessel Cerium Retention Using Ultrasonic Wave Reflective Pattern Analysis and Frequency Diversity Signal Processing (초음파 반사 패턴과 주파수 대역 분할 신호처리를 이용한 다층구조인 노내 간극 측정)

  • Koo, Kil-Mo;Sim, Cheul-Mu;Kim, Jong-Hwan;Kim, Sang-Baik;Kim, Hee-Dong;Park, Chi-Seung
    • Journal of the Korean Society for Nondestructive Testing
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    • 제20권4호
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    • pp.314-321
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    • 2000
  • A gap between a $Al_2O_3/Fe$ thermite and lower head vessel is formed in the lower-plenum arrested vessel attack(LAVA) experiment which is the 1st phase study of simulation of naturally arrested vessel attack in vessel(SONATA-IV). The gap measurement using a conventional ultrasonic method would be lack of a reliability due to the structure complexity and the metallurgical grain size change of the lower head HAZ occurred by a thermite $Al_2O_3/Fe$ melt or a $Al_2O_3$ melt at $2300^{\circ}C$. The grain echoes having false signals and lower S/N ratio signals are detected due to a multiple scattering, a mode conversion and an attenuation of a ultrasonic resulted from at the interface of increased grain size zone. In this test, the signals pattern was classified to understand the behavior of the ultrasonic in a multi-layer specimen of solid-liquid-solid of assuming that the thermite and the lower head vessel is immersed. The polarity threshold algorithm of frequency diversity gives us the enhancement about 6dB of the ratio S/N.

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Analysis of Ferromagnetic Resonance Linewidth in Ni Thin Film Fabricated by Electrodeposition Method (전기 도금법으로 제작한 Ni 박막의 강자성 공명 선폭 분석)

  • Kim, Dong Young;Yoon, Seok Soo
    • Journal of the Korean Magnetics Society
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    • 제24권2호
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    • pp.60-65
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    • 2014
  • We obtained resonance field ($H_{res}$) and linewidth (${\Delta}H_{PP}$) from measured ferromagnetic resonance signal in the functions of polar angle (${\Theta}_H$) in Ni thin film of 240 nm thickness fabricated by electrodeposition method. The angular dependence of $H_{res}$ was well fitted with the calculated ones. We confirmed that the g-factor and effective demagnetization field were 2.18 and 445 emu/cc by the theoretical analysis of the resonance field, respectively. The angular dependence of ${\Delta}H_{PP}$ showed very large values at in-plane direction (${\Theta}_H=90^{\circ}$), which could not explained by the homogenous linewidth due to the Gilbert damping and inhomogeneous linewidth due to the angular variations and magnetization variations by the surface layer. Therefore, we considered the spin wave scattering (two magnon scattering) process in order to analyze the measured inhomogeneous linewidth, which was appeared in thicker film than the critical thickness of 50 nm. The defect medicated spin wave scattering played a key role in the electrodoposited Ni thin film of 240 nm thickness.

Improvement of non-negative matrix factorization-based reverberation suppression for bistatic active sonar (양상태 능동 소나를 위한 비음수 행렬 분해 기반의 잔향 제거 기법의 성능 개선)

  • Lee, Seokjin;Lee, Yongon
    • The Journal of the Acoustical Society of Korea
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    • 제41권4호
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    • pp.468-479
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    • 2022
  • To detect targets with active sonar system in the underwater environments, the targets are localized by receiving the echoes of the transmitted sounds reflected from the targets. In this case, reverberation from the scatterers is also generated, which prevents detection of the target echo. To detect the target effectively, reverberation suppression techniques such as pre-whitening based on autoregressive model and principal component inversion have been studied, and recently a Non-negative Matrix Factorization (NMF)-based technique has been also devised. The NMF-based reverberation suppression technique shows improved performance compared to the conventional methods, but the geometry of the transducer and receiver and attenuation by distance have not been considered. In this paper, the performance is improved through preprocessing such as the directionality of the receiver, Doppler related thereto, and attenuation for distance, in the case of using a continuous wave with a bistatic sonar. In order to evaluate the performance of the proposed system, simulation with a reverberation model was performed. The results show that the detection probability performance improved by 10 % to 40 % at a low false alarm probability of 1 % relative to the conventional non-negative matrix factorization.