34,471 research outputs found
DOI resolution measurement and error analysis with LYSO and APDs
No full textSpatial resolution degradation in PET occurs at the edge of Field Of View (FOV) due to parallax error. To improve spatial resolution at the edge of FOV, Depth-Of-Interaction (DOI) PET has been investigated and several methods for DOI positioning were proposed. In this paper, a DOI-PET detector module using two 8 x 4 array avalanche photodiodes (APDs) (Hamamatsu, S8550) and a 2cm long LYSO scintillation crystal was proposed and its DOI characteristics were investigated experimentally. In order to measure DOI positions, signals from two APDs were compared. Energy resolution was obtained from the sum of two APDs' signals and DOI positioning error was calculated. Finally, an optimum DOI step size in a 2 cm long LYSO were suggested to help to design a DOI-PET. (c) 2008 Elsevier B.V. All rights reserved
Continuous Depth-Of-Interaction Resolution Measurement and Error Analysis with LYSO two APDs
No full text양전자방출단층촬영장치에서 고체형 검출기의 연속적 상호작용 깊이 결정에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 원자력및양자공학과, 2007.2, [ v, 41 p. ]PET is a nuclear imaging technique that measures the spatial and temporal distribution of compounds labeled with a positron emitting radionuclide introduced into a subject to be determined non-invasively. Spatial resolution degradation occurs at the edge of Field Of View (FOV) due to parallax error. To improve spatial resolution at the edge of FOV, Depth-Of-Interaction (DOI) PET has been investigated and there are several methods for DOI positioning.
Among DOI positioning methods, sharing scintillation light output is the cost-effective and accurate method while solid-state photosensors such as Avalanche Photodiodes have been well developed. Avalanche photodiodes have internal gain by impact ionizations in high electric field. High gain and low noise are good characteristics for use in PET.
In this thesis, DOI-PET detector using two APD with LSO scintillation crystal was designed and evaluated, and parameter to affect DOI positioning was investigated. Energy resolution of the designed detector was 12 % in 662 keV photopeak. Comparing photopeak channels of two APD output, DOI position was measured. DOI positioning error was ±2.5 mm. DOI resolution in current DOI-PET systems is still ~ cm. Minimum 4 step positions can be obtained with 2 cm long LSO crystal in this result.한국과학기술원 : 원자력및양자공학과
Okyang Chae-Duporge, "LEE UFAN Espaces non-agis" et "LEE UFAN Untouched Space"
No full textOkyang Chae-Duporge, membre du CREOPS, nous informe de la publication de son livre LEE UFAN Espaces non-agis et de sa traduction anglaise LEE UFAN Untouched Space aux éditions Cercle d'Art. (280 pages, ISBN : 978 2 7022 1054 3 & ISBN : 978 2 7022 1059 8) LEE UFAN Untouched Space Okyang Chae-Duporge / Traduit par Rachel Zerner The South-Korean born artist Lee Ufan made a risky wager early in his career, introducing “non-action” into his work. This notion, which recalls traditional Asian va..
A Simulation Study on Spatial Resolution and Noise Power Spectra of a URA-based Multi-hole Collimator in a Small Gamma Camera
No full textPresently the gamma scintillation camera is widely used in various industrial, environmental and medical diagnostic fields. Two major performance parameters, spatial resolution and noise, are primarily determined by the collimator. The imaging performance of the simple collimator, single pin-hole, and a coded-aperture collimator, uniformly redundant array (URA), are analyzed in this study. Though parallel-hole collimators are used in some medical applications, in principle its performance is equivalent to that of a single-hole collimator and moreover its use is limited to the near-field application only. A coded aperture imaging (CAI) techniques have been proposed for gamma-ray imaging especially for far-field applications such as the astrophysics study or environmental monitoring in order to overcome these limitations of a pin-hole or a parallel-hole collimator. In this study, the simulated gamma images using a monte carlo code, MCNP, were acquired with two different energy windows and two-type and four-different collimators. For the evaluation of spatial resolution and noise power spectra, modulation transfer function (MTF) and normalized noise power spectra (NNPS) were computed for all images. In the result, we found that MTF and NNPS can reflect the different properties of different gamma camera systems
A simulation study on spatial resolutions and sensitivity of a URA-based multi-hole collimator in a small gamma camera
No full textOkyang CHAE-DUPORGE, « LEE UFAN. Espaces non-agis »
No full text« LEE UFAN. Espaces non-agis » par Okyang CHAE-DUPORGE Éditions Cercle d'Art, mars 2017, 280 pages ISBN 978 2 7022 1054 3 Présentation de l’ouvrage Artiste majeur né en Corée du Sud, LEE Ufan a fait un choix risqué dès le début de sa carrière : introduire dans son œuvre le « non-agir ». Cette notion qui évoque les valeurs orientales traditionnelles fait simultanément écho à la quête de la peinture post-minimaliste. A la fin des années soixante, LEE Ufan a été l’un des acteurs du mouvement jap..
Okyang CHAE-DUPORGE, « LEE UFAN. Espaces non-agis »
No full text« LEE UFAN. Espaces non-agis » par Okyang CHAE-DUPORGE Éditions Cercle d'Art, mars 2017, 280 pages ISBN 978 2 7022 1054 3 Présentation de l’ouvrage Artiste majeur né en Corée du Sud, LEE Ufan a fait un choix risqué dès le début de sa carrière : introduire dans son œuvre le « non-agir ». Cette notion qui évoque les valeurs orientales traditionnelles fait simultanément écho à la quête de la peinture post-minimaliste. A la fin des années soixante, LEE Ufan a été l’un des acteurs du mouvement jap..
ALGORITHMS FOR PARTITIONING A GRAPH
No full textThe k-way graph partitioning problem is considered with two efficient heuristic procedures. Algorithms ''local extreme exchange'' (LEE) and ''overall extreme exchange'' (GEE) are presented by modifying Kernighan-Lin's two way uniform partitioning method. In algorithm LEE, a node which maximizes the reduced cost is selected and exchanged with a node in another cluster such that the gain from the exchange with the selected node is maximized. The computational time efficiency of LEE is verified to be excellent compared to Kernighan-Lin's method. Algorithm OEE which considers a node pair that maximizes the reduced exchange cost is illustrated to be superior to the Kernighan-Lin's method. The time requirement of the proposed algorithm is also shown to be smaller than that of Kernighan-Lin's procedure
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