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Digital n-γ Pulse Shape Discrimination in Organic Scintillators with a High-Speed Digitizer
Kim, Chanho,Yeom, Jung-Yeol,Kim, Geehyun The Korean Association for Radiation Protection 2019 방사선방어학회지 Vol.44 No.2
Background: As neutron fields are always accompanied by gamma rays, it is essential to distinguish neutrons from gamma rays in the detection of neutrons. Neutrons and gamma rays can be separated by pulse shape discrimination (PSD) methods. Recently, we performed characterization of a stilbene scintillator detector and an EJ-301 liquid scintillator detector with a high-speed digitizer DT5730 and investigated optimized PSD variables for both detectors. This study is for providing a basis for developing fast neutron/gamma-ray dual-particle imager. Materials and Methods: We conducted PSD experiments using stilbene scintillator and EJ-301 liquid scintillator and evaluated neutron and gamma ray discriminability of each PSD method with a $^{137}Cs$ gamma source and a $^{252}Cf$ neutron source. We implemented digital signal processing techniques to apply two PSD methods - the charge comparison (CC) method and the constant time discrimination (CTD) method - to distinguish neutrons from gamma rays. We tried to find optimized PSD variables giving the best discriminability in a given experimental condition. Results and Discussion: For the stilbene scintillator detector, the charge comparison method and the constant time discrimination method both delivered the PSD FOM values of 1.7. For the EJ-301 liquid scintillator detector, both PSD methods delivered the PSD FOM values of 1.79. With the same PSD variables, PSD performance was excellent in $300{\pm}100keVee$, $500{\pm}100keVee$, and $700{\pm}100keVee$ energy regions. This result shows that we can achieve an effective discrimination of neutrons from gamma rays using these scintillator detector systems. Conclusion: We applied both PSD methods to a stilbene and a liquid scintillator and optimized the PSD performance represented by FOM values. We observed a good separation performance of both scintillators combined with a high-speed digitizer and digital PSD. These results will provide reference values for the dual-particle imager we are developing, which can image both fast neutrons and gamma rays simultaneously.
A Cost-effective Light Emitting Diode-acoustic System for Preclinical Ocular Applications
Hojong Choi,Jaemyung Ryu,Jung-Yeol Yeom 한국광학회 2018 Current Optics and Photonics Vol.2 No.1
Opto-acoustic systems provide structural and functional information regarding biological tissues. Conventional opto-acoustic systems typically employ continuous or pulsed lasers as transmission sources. Compared to lasers, light emitting diodes (LEDs) are cost-effective and relatively portable excitation sources but are non, coherent. Therefore, in this study, a relatively low cost lens - a type of Ramsden eyepiece - was specially designed to theoretically calculate the illumination and achieve a constant brightness across the pupil of an eye. In order to verify the capability of the developed light-emitting diode-acoustic (LEDA) systems, we carried out experiments on bovine and bigeye tuna eyeball samples, which are of similar size to the human eye, using low frequency (10 MHz) and high frequency (25 MHz) ultrasound transducers. High frequency ultrasound transducers are able to provide higher spatial resolution compared to low frequency ultrasound transducers at the expense of penetration depth. Using the 10 MHz and 25 MHz ultrasound transducers, acceptable echo signals (3.82, 3.94, and 5.84 mV at 10 MHz and 282, 1557, 2356 mV at 25 MHz) from depth greater than 3 cm and 6 cm from the anterior surface of the eye were obtained. We thereby confirmed that the LEDA system using a pulsed LED with the designed Ramsden eyepiece lens, used in conjunction with low and high frequency ultrasound transducers, has the potential to be a cost-effective alternative method, while providing adequate acoustic signals from bovine and bigeye tuna ocular areas.
IMIPENEM/CILASTATIN(TIENAM)의 임상적 연구
오상미,염정필,곽재용,임창열,이양근 의과학연구소 1997 全北醫大論文集 Vol.21 No.2
The rapid institution of broad-spectrum antibiotics in febrile neutropenic patients has clearly been shown to limit infectious morbidity and mortality. Imipenem is the first representative of the new thienamycin class of antibiotics. It has an extremely broad antimicrobial spectrum that includes most of the gram-negative and gram-positive organisms that commonly cause infections in neutropenic patients. We have evaluated imipenem as initial therapy for febrile patients with neutropenia and also as secondary therapy in patients failing to respond to other antimicrobial regimen. Clinical response rate was 75%. No serious side effects were noted in any patients. In conclusion, imipenem/cilastatin is a safe and effective antibiotics as monotherapy in febrile granulocytopenic patients.
항 우울제 치료로 호전을 보인 흉통이 동반된 호두까기 식도증 1 예
최석채(Suck Chei Choi),이상열(Sang Yeol Lee),최지훈(Ji Hun Choi),심미령(Mi Ryeong Sim),염주진(Joo Jin Yeom),박정현(Jung Hyeon Park),김태현(Tae Hyeon Kim),나용호(Yong Ho Nah) 대한소화기기능성질환·운동학회 2001 Journal of Neurogastroenterology and Motility (JNM Vol.7 No.2
Nutcracker esophagus is thought to be a common cause of noncardiac chest pain although has not been clearly established, and the effective treatment is lacking. The usual forms of therapy for noncardiac chest pain by nutcracker esophagus have been directed traditionally toward reducing esophageal hypermotility and muscle tone such as nitrate and calcium channel blocker. However, the results of this treatment in the long term care of patient with esophageal symptoms have been generally disappointing and often unsatisfactory. Recently, psychosomatic aspect of esophageal motility disorder including antidepressant treatment has been accepted in the treatment of noncardiac chest pain. We report a 48 year old female with nutcracker esophagus associated chest pain by ambulatory 24 hour esophageal manometry who failed diagnosis by conventional manometry. The symptoms of chest pain, quality of life, and depression of the patient were improved after antidepressant medication. (Korean Journal of Gastrointestinal Motility 2001;7:227-232)
Programmable High Voltage Distribution for Photodetectors in a 1?mm Resolution Clinical PET System
Lau, Frances W. Y.,Vandenbroucke, Arne,Jung-Yeol Yeom,Reynolds, Paul D.,Hsu, David,Innes, Derek,Levin, Craig S. Professional Technical Group on Nuclear Science 2015 IEEE transactions on nuclear science Vol.62 No.5
<P>We present a scalable, cost-effective, and compact high voltage (HV) distribution design for a system that requires many HV channels for photodetector biasing. A digital-to-analog converter (DAC) with a 100 V output range is floated with its reference at -1800 V, providing outputs between -1800 V and -1700 V. As a consequence, the DAC control and power signals are referenced to -1800 V. This design was implemented in our 1 mm resolution clinical PET imaging system with detectors comprised of LYSO scintillation crystals coupled to position-sensitive avalanche photodiodes (PSAPDs). The programmable bias voltage outputs have only 20 m V<SUB>pp</SUB> of bias ripple. This design enables all PSAPDs to be biased at their optimal bias voltage, allowing us to achieve a standard deviation of only 2.3% in the energy resolution measured across all 512 PSAPDs in the subsystem.</P>
Simulation study of a novel target oriented SPECT design using a variable pinhole collimator
Bae, Seungbin,Chun, Jaehee,Cha, Hyemi,Yeom, Jung Yeol,Lee, Kisung,Lee, Hakjae Published for the American Association of Physicis 2017 Medical physics Vol.44 No.2
<P>Conclusions: In this study, we designed a novel pinhole collimator for SPECT and presented preliminary results of target oriented imaging with a simulation study. Currently, we are pursuing strategies to realize the proposed system, with the goal to apply the technology into a high-sensitivity and high-resolution preclinical SPECT. Should VP SPECT be applied to the clinical setting, we anticipate a high-sensitivity, high-resolution system for applications such as heart dedicated SPECT or related fields. (C) 2016 American Association of Physicists in Medicine</P>
Son, Jun Seong,Song, Jae-Hoon,Ko, Kwan Soo,Yeom, Joon Sup,Ki, Hyun Kyun,Kim, Shin-Woo,Chang, Hyun-Ha,Ryu, Seong Yeol,Kim, Yeon-Sook,Jung, Sook-In,Shin, Sang Yop,Oh, Hee Bok,Lee, Yeong Seon,Chung, Doo The Korean Academy of Medical Sciences 2010 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.25 No.7
<P>Recent changes in healthcare systems have changed the epidemiologic paradigms in many infectious fields including bloodstream infection (BSI). We compared clinical characteristics of community-acquired (CA), hospital-acquired (HA), and healthcare-associated (HCA) BSI. We performed a prospective nationwide multicenter surveillance study from 9 university hospitals in Korea. Total 1,605 blood isolates were collected from 2006 to 2007, and 1,144 isolates were considered true pathogens. HA-BSI accounted for 48.8%, CA-BSI for 33.2%, and HCA-BSI for 18.0%. HA-BSI and HCA-BSI were more likely to have severe comorbidities. <I>Escherichia coli</I> was the most common isolate in CA-BSI (47.1%) and HCA-BSI (27.2%). In contrast, <I>Staphylococcus aureus</I> (15.2%), coagulase-negative <I>Staphylococcus</I> (15.1%) were the common isolates in HA-BSI. The rate of appropriate empiric antimicrobial therapy was the highest in CA-BSI (89.0%) followed by HCA-BSI (76.4%), and HA-BSI (75.0%). The 30-day mortality rate was the highest in HA-BSI (23.0%) followed by HCA-BSI (18.4%), and CA-BSI (10.2%). High Pitt score and inappropriate empirical antibiotic therapy were the independent risk factors for mortality by multivariate analysis. In conclusion, the present data suggest that clinical features, outcome, and microbiologic features of causative pathogens vary by origin of BSI. Especially, HCA-BSI shows unique clinical characteristics, which should be considered a distinct category for more appropriate antibiotic treatment.</P>