• 천문학회보
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• 제31권2호
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• pp.28.1-28.1
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• 2006

• 대한디지털의료영상학회논문지
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• 제15권2호
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• pp.55-61
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• 2013

The purpose of this study is to evaluate image blurring according to variation of the ETL and propose the clinically appropriate ETL range. SIEMENS MAGNETOM Skyra 3.0T and 20 channel head coil were used for the study. MRI phantom was kept the lines horizontally to three direction(X,Y,Z) of the coil and T1, T2 weighted images that used the fast spin echo technique acquired. The ETL with increase of 10 was applied from 10 to 80. In addition, the ETL with increase of 1 was applied in the interval statistically significant differences occurred. And T1, T2 weighted images that used the conventional spin echo technique acquired to compare image blurring of the images that used the fast spin echo technique. The slope of lattice in the images was measured using Image J 1.47v program to evaluate image blurring. And image blurring was determined by the degree of the slope. The statistical significance of both techniques was evaluated by the Kruskal-Wallis test of the SPSS 17.0v. And the correlation of the ETL and image blurring was evaluated quantitatively by regression analysis. The slope of the T1, T2 weighted images that used fast spin echo technique decreased as contrasted with conventional spin echo technique. In the result of the Kruskal-Wallis test, the T1, T2 weighted images that used fast spin echo technique made a significant difference with conventional spin echo technique. Particularly, in the Tomhane' T2 test, the T1, T2 weighted images made a significant difference from ETL 22 and 31 respectively. In the result of the regression analysis, the R-squared of the T1, T2 weighted images are 0.762 and 0.793. It is difficult to apply the long ETL in the T1 weighted image caused by the short TR and multi-slices study. Therefore, clinical impact according to variation of the ETL is very slight in the T1 weighted images. But the application of the proper ETL is demanded in T2 weighted images using the fast spin echo technique in order to prevent image blurring.

• 한국멀티미디어학회논문지
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• 제19권2호
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• pp.200-208
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• 2016

Compressed sensing is a signal processing technique for efficiently acquiring and reconstructing in an under-sampled (i.e., under Nyquist rate) representation. A block compressed sensing with projected Landweber (BCS-SPL) framework is most widely known, but, it has high computational complexity at decoder side. In this paper, by introducing adaptive exit criteria instead of fixed exit criteria to SPL framework, an effective fast algorithm is designed in such a way that it can utilize efficiently the sparsity property in DCT coefficients during the iterative thresholding process. Experimental results show that the proposed algorithm results in the significant reduction of the decoding time, while providing better visual qualities than conventional algorithm.

• 천문학회보
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• 제38권2호
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• pp.88.2-88.2
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• 2013

Exploration of the wave-mode identification and its propagating property in the solar pore is desirable to study the energy transfer in the solar atmosphere. The Fast Imaging Solar Spectrograph (FISS) installed at the New Solar Telescope (NST) is a unique system that can do imaging of H-alpha and Ca II 8542 band simultaneously, which is quite suitable for studying of dynamics of chromosphere. In this study, we inspect a relationship between the cross-sectional area and intensity of the pore at continuum (-0.4 nm) near the Ca II line. We find coherent oscillations of the area and intensity. They shows out-of-phase (~ 180 degree difference) in photosphere, which implies that the oscillation is fast sausage mode. We also investigate a relationship between LOS velocities above the pore obtained from the Ca II and the Ha line cores, and find no significant difference of the phase (~10 degree) between the formation heights of the lines in chromosphere.

• 천문학회보
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• 제38권2호
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• pp.92.1-92.1
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• 2013

In this study, we examined chromospheric oscillation signatures in two solar active regions, a limb active region and a sunspot with a light bridge, observed by the Fast Imaging Solar Spectrograph (FISS) of the 1.6m New Solar Telescope (NST) at Big Bear Solar Observatory. The FISS is a slit spectrograph with a fast imaging capability and can observe the solar chromosphere in $H{\alpha}$ and Ca II $8542{\AA}$ bands simultaneously with high spectral resolutions. After dark and flat correction, we compensated for image rotation at the Coude focus and made image alignment. We estimated Doppler shifts over active regions using the bisector method and investigated the temporal and spatial fluctuations of Doppler shifts for some selected cases. And we obtain the power map by using the Lomb-Scargle periodogram technique to examine the oscillation power at different features. Finally, we will discuss our results and implications.

• 제어로봇시스템학회논문지
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• 제16권11호
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• pp.1044-1052
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• 2010

In this paper, a new realtime algorithm called the RTPBTD-HPDAF (Recursive Temporal Profile Base Target Detection with Highest Probability Data Association Filter) is presented for tracking fast moving small targets with IIR (Imaging Infrared) sensor systems. Spatial filter algorithms are mainly used for target in IIR sensor system detection and tracking however they often generate high density clutter due to various shapes of cloud. The TPBTD (Temporal Profile Base Target Detection) algorithm based on the analysis of temporal behavior of individual pixels is known to have good performance for detection and tracking of fast moving target with suppressing clutter. However it is not suitable to detect stationary and abruptly maneuvering targets. Moreover its computational load may not be negligible. The PTPBTD-HPDAF algorithm proposed in this paper for real-time target detection and tracking is shown to be computationally cheap while it has benefit of tracking targets with abrupt maneuvers. The performance of the proposed RTPBTD-HPDAF algorithm is tested and compared with the spatial filter with HPDAF algorithm for run-time and track initiation at real IIR video.

• Investigative Magnetic Resonance Imaging
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• 제19권1호
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• pp.19-30
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• 2015

Purpose: A new compressed sensing technique by iterative truncation of small transformed coefficients (ITSC) is proposed for fast cardiac CINE MRI. Materials and Methods: The proposed reconstruction is composed of two processes: truncation of the small transformed coefficients in the r-f domain, and restoration of the measured data in the k-t domain. The two processes are sequentially applied iteratively until the reconstructed images converge, with the assumption that the cardiac CINE images are inherently sparse in the r-f domain. A novel sampling strategy to reduce the normalized mean square error of the reconstructed images is proposed. Results: The technique shows the least normalized mean square error among the four methods under comparison (zero filling, view sharing, k-t FOCUSS, and ITSC). Application of ITSC for multi-slice cardiac CINE imaging was tested with the number of slices of 2 to 8 in a single breath-hold, to demonstrate the clinical usefulness of the technique. Conclusion: Reconstructed images with the compression factors of 3-4 appear very close to the images without compression. Furthermore the proposed algorithm is computationally efficient and is stable without using matrix inversion during the reconstruction.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.208-215
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• 2021

Cosmic-ray muon scattering tomography (MST) technology is a new radiation imaging technology with unique advantages. As the performance of its image reconstruction algorithm has a crucial influence on the imaging quality, researches on this algorithm are of great significance to the development and application of this technology. In this paper, a fast inspection algorithm based on clustering analysis for the identification of the existence of nuclear materials is studied and optimized. Firstly, the principles of MST technology and a binned clustering algorithm were introduced, and then several simulation experiments were carried out using Geant4 toolkit to test the effects of exposure time, algorithm parameter, the size and structure of object on the performance of the algorithm. Based on these, we proposed two optimization methods for the clustering algorithm: the optimization of vertical distance coefficient and the displacement of sub-volumes. Finally, several sets of experiments were designed to validate the optimization effect, and the results showed that these two optimization methods could significantly enhance the distinguishing ability of the algorithm for different materials, help to obtain more details in practical applications, and was therefore of great importance to the development and application of the MST technology.

• 한국산학기술학회논문지
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• 제14권9호
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• pp.4313-4319
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• 2013

본 연구는 흑혈류영상 획득에서 고속스핀에코기법의 신호소실 현상을 이용하여 검사시간을 최소화시켜 환자의 불편을 줄이고 진단적 가치를 유지하고자 하였다. 연구방법은 흑혈류영상을 획득한 환자 32명을 대상으로, 기존의 이중역전회복기법과 새로운 기법인 고속스핀에코기법을 각각 적용한 후, 기법에 따른 혈류의 신호소거 차이를 알아보기 위해 T1, T2 강조영상에서 내경동맥 내강의 SNR과 CNR을 비교 평가하였다. 연구결과, SNR은 고속스핀에코기법이 이중역전회복기법 보다 T1, T2 강조영상에서 11.49%(4.73), 13.66%(6.03) 낮았으며, CNR은 고속스핀에코기법이 T1 강조영상에서 8.69%(15.04) 높았고, T2 강조영상에서 7.55% (13.17) 낮았으나, 통계적 수준에서 두 기법간의 SNR과 CNR의 차이는 유의하지 않았다. 그러므로 흑혈류영상 획득 시 고속스핀에코기법을 이용한다면 진단적 가치는 유지하면서 검사시간을 최소화하여 환자의 불편을 줄일 수 있다고 판단된다.

• Investigative Magnetic Resonance Imaging
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• 제12권2호
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• pp.142-147
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• 2008

목적 : 본 연구는 핵자기공명 분광기를 개조한 미세영상 기법을 이용하여, 동물실험에 주류를 이루는 mouse를 대상으로, 0.1 mm 이내의 초고해상도 자기공명영상을 5분 정도 시간 안에 획득할 수 있는 방법을 개발하고자 하였다. 대상 및 방법 : 사용된 mouse는 C57BL/6로서 무게 50 그램 이내의 mouse를 사용하였다. 본 연구에 활용된 초전도 자석은 구경 89 mm, 4.7 T의 자기장 세기를 가진 수직형 자석이며, 사용된 샘플 코일의 직경은 30 mm 이고, 사용된 펄스시퀀스는 fast spin echo (FSE) 및 gradient echo (GE) 기법들이다. 결과 : 최적의 자기공명영상 파라미터를 확보하면서 2차원 영상으로서 수소밀도 및 T2 강조 영상을 획득하였다. 영상으로부터 mouse 뇌의 미세부분까지 상세히 해부학적 구조를 확인할 수 있었고, 또한 입체적인 정보를 획득하기 위하여 3D 영상도 부가적으로 획득하였다. 조영제를 이용한 dynamic contrast 연구에 3D 영상이 매우 유용하였다. 결론 : 본 연구를 통하여 mouse 뇌에 대한 고해상도 자기공명영상 획득을 위한 최적의 파라미터를 확보할 수 있었고, 또한 성공적인 자기공명영상도 획득하였다. 즉, 사람이나 다른 소동물뇌의 경우와 같이 mouse 뇌 조직의 다양한 부위의 미세부분을 확인할 수 있는 충분한 고해상도의 영상을 획득하였다. 최근 국내에서 mouse를 이용한 자기공명영상 연구가 시작되었으나 아직 초기단계라고 평가할 수 있고, mouse는 다른 동물에 비하여 취급/관리하기 쉬우므로 향후 mouse를 이용한 뇌 연구가 활성화 될 것으로 사료된다.