• Journal of Gastric Cancer
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• 제12권3호
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• pp.179-186
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• 2012

Purpose: The use of 18F-2-deoxy-2-fluoro-D-glucose positron emission tomography-computed tomography as a routine preoperative modality is increasing for gastric cancer despite controversy with its usefulness in preoperative staging. In this study we aimed to determine the usefulness of preoperative positron emission tomography-computed tomography scans for staging of gastric cancer. Materials and Methods: We retrospectively analyzed 396 patients' positron emission tomography-computed tomography scans acquired for preoperative staging from January to December 2009. Results: The sensitivity of positron emission tomography-computed tomography for detecting early gastric cancer was 20.7% and it was 74.2% for advanced gastric cancer. The size of the primary tumor was correlated with sensitivity, and there was a positive correlation between T stage and sensitivity. For regional lymph node metastasis, the sensitivity and specificity of the positron emission tomography-computed tomography were 30.7% and 94.7%, respectively. There was no correlation between T stage and maximum standardized uptake value or between tumor markers and maximum standardized uptake value. Fluorodeoxyglucose uptake was detected by positron emission tomography-computed tomography in 24 lesions other than the primary tumors. Among them, nine cases were found to be malignant, including double primary cancers and metastatic cancers. Only two cases were detected purely by positron emission tomography-computed tomography. Conclusions: Positron emission tomography-computed tomography could be useful in detecting metastasis or another primary cancer for preoperative staging in gastric cancer patients, but not for T or N staging. More prospective studies are needed to determine whether positron emission tomography-computed tomography scans should be considered a routine preoperative imaging modality.

• Applied Science and Convergence Technology
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• 제25권5호
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• pp.85-87
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• 2016

Coincidence Doppler broadening and positron lifetime methods in positron annihilation spectroscopy has been used to analyze defect structures in metal, semiconductor and polycrystal, respectively. The S parameter and the lifetime (${\tau}$) value show that the defects were strongly related with vacancies. A positive relationship existed between the scanning electron microscope (SEM) images and the positron annihilation spectroscopy (PAS). According to the SEM images and PAS results, measurements of the defects with PAS indicate that it was more affected by the defect than the purity.

• 한국재료학회지
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• 제20권6호
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• pp.307-311
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• 2010

Positron annihilation lifetime spectroscopy is applied to BaSrFBr : Eu film which is used for the phosphore layer, and afterwards the reliability and self-consistency of source corrections in the positron lifetime spectroscopy is investigated using a $^{22}Na$ positron emitter covered by thin foils. The positron lifetime showed no significant change through the various proton irradiation energies. It is unusual that the measurements of the defects indicate that most of the defects were likely to have been generated by X-ray radiation. This may have resulted from the Bragg peaks of the proton characteristics. The Bragg peak does not affect the defect signals enough to distinguish the lifetimes and intensities in a material that is includes multi-grains. The lifetime ($\tau_1$) associated with positron annihilations in the Ba, Br, and Eu of the sample was about 250 ps, and due to the annihilations at F-centers or defects from the irradiated protons in sample, the lifetime ($\tau_2$) was about 500 ps.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.195-198
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• 2002

A positron camera, consisting of a pair of Anger-type scintillation detectors, has been developed for verifying the ranges of irradiation beams in heavy-ion radiotherapy. Images obtained by a centroid calculation of photomultiplier outputs exhibit a distortion near the edge of the crystal plane in an Anger-type scintillation detector. The images of a $\^$68/Ge line source were detected and look-up tables were prepared for the position correction parameters. Asymmetry of the position distribution detected by the positron camera was prevented with this correction. As a result, a linear position response and a position resolution of 8.6 mm were obtained over a wide measurement field.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1979년도 하계 전자.전기연합학술발표회논문집
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• pp.162-163
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• 1979

A new detector array scheme for the positron camera for tile improved image resolution and a method for the resolution improvement of the undersampled projection data from ring positron camera are proposed. Computer simulation results are presented and problems ana limitations are discussed.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.859-863
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• 2003

We report on the theoretical positron affinities of closed-shell atomic anions. The second-order many-body perturbation theory is applied taking the positron-electron interaction as a perturbation. The corrections for the complete basis set effects to the second order affinity are calculated based on the variational and nonvariational energy functionals of explicitly correlated geminals. It is shown that the explicitly correlated methods accelerate the convergence of the expansion significantly giving the account of the cusp behavior outside the orbital space.

• 대한핵의학회지
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• 제36권1호
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• pp.28-33
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• 2002

Lung cancer has become a loading cause of cancer death in Korea. Positron emission tomography was introduced in clinical nuclear medicine in the early 1990s and many studios using this functional imaging technology were performed for evaluation of its clinical utility. I review the current role of positron emission tomography in the diagnosis, staging, and therapy monitoring of lung cancer.

• 한국멀티미디어학회논문지
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• 제19권8호
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• pp.1371-1376
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• 2016

In this paper, an iterative method is proposed to perform attenuation correction and image reconstruction simultaneously for positron emission tomography, by using the time-of-flight information. Numerical simulation results are presented to demonstrate an improved performance of the proposed method in attenuation correction and image reconstruction.

• 한국진공학회지
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• 제21권5호
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• pp.225-232
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• 2012

수명 측정법과 동시 계수 도플러 넓어짐 양전자 소멸 분광법으로 p형과 n형 실리콘 시료에 3.98 MeV 에너지를 가진 $0.0{\sim}20.0{\times}10^{13}\;protons/cm^2$ 양성자 빔 조사에 의한 결함을 측정하여 실리콘 결함 특성에 대하여 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 감마선 스펙트럼의 전자 밀도 에너지를 수리적 해석 방법인 S-변수와 열린 부피 결함에 대한 측정법으로서 양전자 수명 ${\tau}_1$과 ${\tau}_2$, 이에 따른 밀도 $I_1$과 $I_2$를 사용하여, 시료의 구조 변화를 측정하였다. 본 연구에서 측정된 S-변수와 양전자 수명은 시료에 조사된 양성자 조사량의 변화에 따라 결함이 증가하였으며, 양전자 수명 측정과 같은 경향을 보여준다. SRIM의 결과로써, 양성자 조사 에너지에 따른 Bragg 피크 때문에 양성자는 시료의 특정 깊이에 주로 결함을 형성하여 시료 전체에는 결함으로 잘 나타나지 않기 때문이다. 빔의 조사량에 따른 결함의 영향이 더 큰 것으로 나타났다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.33.1-33.1
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• 2007