• Nuclear Medicine and Molecular Imaging
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• v.41 no.3
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• pp.194-200
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• 2007

Purpose: $^{13}N$-ammonia is a well known radiopharmaceutical for the measurement of a myocardial blood flow (MBF) non-invasively using PET-CT. In this study, we investigated a correlation between MBF obtained from dynamic imaging and myocardial perfusion score (MPS) obtained from static imaging for usefulness of cardiac PET study. Methods: Twelve patients (11 males, 1 female, $57.9{\pm}8.6$ years old) with suspicious coronary artery disease underwent PET-CT scan. Dynamic scans (6 min: $5\;sec\;{\times}\;12,\;10\;sec\;{\times}\;6,\;20\;sec\;{\times}\;3,\;and\;30\;sec\;{\times}\;6$) were initiated simultaneously with bolus injection of 11 MBq/kg $^{13}N-ammonia$ to acquire rest and stress image. Gating image was acquired during 13 minutes continuously. Nine-segment model (4 basal walls, 4 mid walls, and apex) was used for a measurement of MBF. Time activity curve of input function and myocardium was extracted from ROI methods in 9 regions for quantification. The MPS were evaluated using quantitative analysis software. To compare between 20-segment model and 9-segment model, 6 basal segments were excluded and averaged segmental scores were used. Results: There are weak correlation between MBF (rest, 0.18-2.38 ml/min/g; stress, 0.40-4.95 ml/min/g) and MPS (rest 22-91%, stress, 14-90%), however the correlation coefficient between corrected MBF and MPS in rest state was higher than stress state (rest r=0.59; stress r=0.80). As a thickening increased, correlation between MBF and MPS also showed good correlation at each segments. Conclusions: Corrected and translated MPS as its characteristics using $^{13}N$-ammonia showed good correlation with absolute MBF measured by dynamic image in this study. Therefore, we showed MPS is one of good indices which reflect MBF. We anticipate PET-CT could be used as useful tool for evaluation of myocardial function in nuclear cardiac study.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.6
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• pp.444-450
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• 2008

Purpose: The aim of this study was to evaluate the usefulness of whole body positron emission tomography (PET) using $^{18}F-fluorodeoxyglucose$ ($^{18}F-FDG$) for cancer screening in asymptomatic subjects. Materials and Methods: The subjects were 1,762 men and 259 women who voluntarily underwent $^{18}F-FDG$ PET for cancer screening as a part of a routine health examination. Final diagnosis was decided by other diagnostic studies, pathological results or clinical follow-up for 1 year. Results: Of 2,021 subjects, 40 (2.0%) were finally proved to have cancer. Abnormal focal $^{18}F-FDG$ uptake suggesting malignancy was found in 102 subjects (5.0%). Among them, 21 subjects (1.0%) were proved to have cancer. Other tests in the routine health examination could not find 9 of 21 cancers (42.9%) detected by PET. The sensitivity, specificity, positive predictive value, and negative predictive value of PET for cancer screening were 52.5%, 95.9%, 20.6%, and 99.0%, respectively. Pathologies of cancers missed on PET were adenocarcinoma (n = 9; 3 colon cancers, 3 prostate cancers, 2 stomach cancers, and 1 rectal cancer), differentiated thyroid carcinoma (n = 6), bronchioalveolar cell carcinoma (n = 2), urinary bladder cancer (n = 1), and melanoma (n = 1). More than half of cancers which were not detected by PET were smaller than 1 cm in diameter. Conclusion: $^{18}F-FDG$ PET might be useful for cancer screening in asymptomatic subjects due to its high specificity and negative predictive value and playa supplementary role to the conventional health check-up, but it could not replace due to limited sensitivity for urological cancers, small-sized tumors and some hypometaboic cancers.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.6
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• pp.469-477
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• 2008

Purpose: The goal of this paper is to present the design and performance of a position encoding circuit for $16{\times}16$ array of position sensitive multi-anode photomultiplier tube for small animal PET scanners. This circuit which reduces the number of readout channels from 256 to 4 channels is based on a charge division method utilizing a resistor array. Materials and Methods: The position encoding circuit was simulated with PSpice before fabrication. The position encoding circuit reads out the signals from H9500 flat panel PMTs (Hamamatsu Photonics K.K., Japan) on which $1.5{\times}1.5{\times}7.0\;mm^3$ $L_{0.9}GSO$ ($Lu_{1.8}Gd_{0.2}SiO_{5}:Ce$) crystals were mounted. For coincidence detection, two different PET modules were used. One PET module consisted of a $29{\times}29\;L_{0.9}GSO$ crystal layer, and the other PET module two $28{\times}28$ and $29{\times}29\;L_{0.9}GSO$ crystal layers which have relative offsets by half a crystal pitch in x- and y-directions. The crystal mapping algorithm was also developed to identify crystals. Results: Each crystal was clearly visible in flood images. The crystal identification capability was enhanced further by changing the values of resistors near the edge of the resistor array. Energy resolutions of individual crystal were about 11.6%(SD 1.6). The flood images were segmented well with the proposed crystal mapping algorithm. Conclusion: The position encoding circuit resulted in a clear separation of crystals and sufficient energy resolutions with H9500 flat-panel PMT and $L_{0.9}GSO$ crystals. This circuit is good enough for use in small animal PET scanners.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.101-115
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• 2018

This study was carried out to evaluate the effects of various filter conditions on unconfined aquifer (alluvial aquifer). We made model test device which has filter layer, pumping well and observation well which consist of sand layer and gravel layer to test. Step drawdown test and long term pumping tests were carried out using the device. The permeability characteristics of each test group were confirmed and the optimal yield was calculated. As a result of comparing the optimal yield of double filter and single filter in sand, dual-filter SD-300 was valued at 216.8 % higher final optimal yield than single-filter SS-300. Comparing the dual filter SD-300 and the single filter SS-100 with a thin filter layer, dual-filter SD-300 was valued at 709.2% higher final optimal yield than single-filter SS-300. As a result of analysis of optimal yield change over time, It was confirmed that the ratio of optimal yield of single filter and dual filter increase over time. In order to evaluate the long-term change in water intake efficiency, we considered the point at which the initial optimal yield was reduced by 50%. The dual filter SD-300 is about 351.1% higher than SS-300, which is the same thickness filter, and about 579.0% higher than SS-100. From these results, Assuming that the point at which the initial quantity of water intake is reduced to 50% is the well life, double filters are expected to increase their lifespan by about 3.5 times over single filters of the same thickness and by about 5.8 times over typical single filter. These results can be used to design wells to river bank filtration or filtered seawater. In addition, it is possible to clarify the effect of the double filter through the comparison with the future field test results.

• Ecology and Resilient Infrastructure
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• v.3 no.3
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• pp.201-206
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• 2016

The purpose of this study is to find the regeneration method of filter media using physical and chemical treatment for restoration of phosphorus adsorption ability. The filtration material used in this study is called Adphos. In an experiment of heating treatment, re-used filter media is heated to a high temperature before the adsorption test. The results show that the $PO{_4}^{3-}-P$ adsorption capacity is in the range of 0.0021 - 0.0030 mg/g and the removal efficiency is in the range of 26.1 - 39.4%. In the experiment of acid or basic treatment, re-used filter media is exposed to a different pH condition before the adsorption test. The results show that the $PO_4^{3-}-P$ adsorption capacity is in the range of 0.0010 - 0.0066 mg/g and the removal efficiency is in the range of 15.8 - 87.1% after the acid treatments which have pH values of 1 - 5. However, after the basic treatments which have pH values of 8 - 11, the results show that the $PO{_4}^{3-}-P$ adsorption capacity is in the range of 0.0018 - 0.0034 mg/g and the removal efficiency is in the range of 26.7 - 48.0%. In an experiment of chemical treatment using NaCl, re-used filter media was exposed to a different NaCl concentration before the adsorption test. The results show that the $PO{_4}^{3-}-P$ adsorption capacity is in the range of 0.0036 - 0.0050 mg/g and the removal efficiency is in the range of 50.5 - 71.1%. In conclusion, chemical treatment using NaCl shows a high recovery probability of phosphorus adsorption ability of filter media.

• Applied Microscopy
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• v.30 no.2
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• pp.193-204
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• 2000

Nowadays, mongolian gerbil is widely utilized in the research of brain and water deprivation because of congenitally incomplete Willis' circle, audiogenic seizure in low noise, and special cholesterol metabolism without water absorption for a long time. In this study, we intended to identify the time lapse changes in the general morphoogy and ultrastructure of the catecholaminergic neurons of mongolian gerbil brain in after long-term water deprivation. Fifteen mongolian gerbils were divided into 3 groups (5, 10, and 20-day water deprivation groups), each with 5 mongolian gerbils. Additional 5 mongolian gerbils which received water without limitation were used as a control. The brain sections were immunostained using tyrosine hysroxylase (TH), $ dopamine-\beta-hydroxylase$ (DBH), and phenylethanolamine-N-methyltrasferase (PMNT) antibodies. And immunoreactive cells were observed by electromicroscopy for the ultrastructural changes . The TH-immunoreactive (TH-IR) nerve cells were observed in the para- and peri-ventricular nucleus of the 3 rd ventricle in the hypothalamus and the substantia nigra. The number of TH-IR neurons in these areas was decreased from the 5th day of the water deprivation to the 10 th day and reincreased until 20 th day water deprivation. The shape and density of the dopamine-secreting cells identified by immunohistochemistry showed changes in the continuous water deprivation. Electron microscopy revealed a round nucleus in the neurons of control group but 5-day water deprivation group showed a dense and irregularly shaped nucleus. Also in the 5-day water-deprived group, mitochondria was decreased in number and junctins were disappered. Endoplasmic reticulum, Golgi complex did not show changes after water-deprivation. In this results, we can conclude that dopamine are involved in the water metabolism in mongolian gerbil, and mongolian gerbil could be used as an animal model for the researches of water deprivation.

• Development and Reproduction
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• v.10 no.1
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• pp.1-7
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• 2006

Ovarian follicular atresia in mammals is finely regulated by gonadotropins and sex steroid hormones. It is well known that granulosa cell pyknosis is a common cytological feature of atretic follicles in the ovary. The present study hypothesized that granulosa cell pyknosis during follicular atresia might be related to apoptotic process and associated with caspase-3 activation. Healthy (normal) and atretic follicles were isolated from porcine ovaries based on macro-morphological criteria. Isolated follicles were either processed for histological observation or used for collection of granulosa cells by aspiration. Hoechst 33258 staining of the cells showed a significantly higher number of fragmented nuclei, a typical morphological feature of apoptotic cell, in granulosa cells from atretic follicles than those from healthy follicles. In addition, the rate of cell death was significantly higher in granulosa cells from atretic follicles than healthy follicles, as measured by flow-cytometric cell cycle analysis. In situ detection of apoptotic cells by TUNEL revealed that apoptosis was mostly restricted to granulosa cells in follicles. Theca cells were TUNEL-negative. Finally, it has been shown by caspase-3 activity assay that granulosa cells from atretic follicles retain a higher caspase-3 activity compared to healthy follicles. Taken together, it is suggested that granulosa cell degeneration during folliclar atresia occurs by caspase-3-dependent apoptotic fashion.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.487-502
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• 2012

This paper is focused on mineral compositions, microstructures and distributional characters of remained grains in the fault rocks collected from a fault developed in Yongdang-ri, Yangbuk-myeon, Gyeongju City, Korea, using X-ray diffraction (XRD), optical microscope, laser grain size analysis and fractal dimension analysis methods. The exposed fault core zone is about 1.5 meter thick. On the average, the breccia zone is 1.2 meter and the gouge zone is 20cm thick, respectively. XRD results show that the breccia zone consists predominantly of rock-forming minerals including quartz and feldspar, but the gouge zone consists of abundant clay minerals such as chlorite, illite and kaolinite. Mineral vein, pyrite and altered minerals commonly observed in the fault rock support evidence of fault activity associated with hydrothermal alteration. Fractal dimensions based on box counting, image analysis and laser particle analysis suggest that mineral grains in the fault rock underwent fracturing process as well as abrasion that gave rise to diminution of grains during the fault activity. Fractal dimensions(D-values) calculated by three methods gradually increase from the breccia zone to the gouge zone which has commonly high D-values. There are no noticeable changes in D-values in the gouge zone with trend being constant. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. It means that the bulk-crushing process of mineral grains in the breccia zone was predominant, whereas abrasion of mineral grains in the gouge zone took place by continuous fault activity. Mineral compositions in the fault zone and peculiar trends in grain distribution indicate that multiple fault activity had a considerable influence on the evolution of fault zones, together with hydrothermal alteration. Meanwhile, fractal dimension values(D) in the fault rock should be used with caution because there is possibility that different values are unexpectedly obtained depending on the measurement methods available even in the same sample.

• Health Policy and Management
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• v.2 no.1
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• pp.17-41
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• 1992

During the month of October, 1990, 676 practicing physicians in Taegu City were surveyed by mail questionnaires about their general characteristics and the reasons why they chose Taegu as a practice location and 331 out of them responded completely. Collected data were analyzed to provide basic reference data for future health manpower policy which intends to solve the problem of geographical maldistribution of physicians, The major findings are as follows: For the question asking why Taegu area is favored, following lists are as the order of their magnitude of the reasons replied by more than 20% of the respondents: 1) Taegu is a foundation of life until now(81.3%) 2) Better educational environments are available for their offsprings(73.7%) 3) They can have intimate relationship with acquaintances or friends sharing same or similar interests(61.0%) 4) Due to characteristics of their specialty, metropolitan seems to fit better(52.0%), 5) They graduated from the medical school in Taegu(49.8%) 6) Never thought of selecting practice location in other area than Taegu without any specific reasons(45.9%) 7) Intelligent communications are available with other physicians(39.9%) 8) More opportunities to participate in social life, such as medical, or alumni association etc., can be given(33.2%) 9) No specific knowledge or relationships with other area are available(32.6%) 10) They finished internship or residency training in Taegu area(31.4%) 11) Facilitation of transferring patients including emergent patients can be obtained (30.8%) 12) Continuing medical educational programs are available(29.9%) 13) Sufficient medical demands are provided because of the large population(28.1%) 14) More chances to be grown up as a medical professionals can be achieved(25.7%) 15) More leizure time can be utilized for cultural activities(23.9%) 16) They had experiences to work in hospitals or facilities in Taegu area(23.3%) 17) Medical facilities of fellow physicians or alumni can be used(20.5%) In addition, 37% of female physicians answered that their spouse strongly influenced them to choose Taegu, and 33.3% of physicians with age of thirty replied that parents did so. Physicians of specialty in radiology, clinical pathology, anatomical pathology, and anesthesiology considered that patients from other hospitals and medical facilities would be referred often to them and that less competition seemed to be expected in their specialty (30.8%). In contrast, general practitioners anticipated that larger population would increase the medical demand(62.5%). 28.6% of medical practitioners who graduated medical schools in other are than Taegu and 22.0% of medical practitioners who were trained in hospitals of other area than Taegu were influenced to choose Taegu by their spouses. In consideration of above findings, we may conclude that long term and rational manpower policies should be implemented to solve the problem of geographical maldistribution of physicians as well as short term physician-inducing policies, and they have to be incorporated with equitable community development.

• Journal of Hospice and Palliative Care
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• v.17 no.3
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• pp.179-184
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• 2014

Purpose: We investigated the safety and efficacy of peripherally inserted central catheters (PICCs) in terminally ill cancer patients. Methods: A retrospective review was conducted on patients who underwent PICC at the hospice-palliative division of KEPCO (Korea Electric Power Corporation) Medical Center between January 2013 and December 2013. All PICCs were inserted by an interventional radiologist. Results: A total of 30 terminally ill cancer patients received the PICC procedure during the study period. Including one patient who had had two PICC insertions during the period, we analyzed a total of 31 episodes of catheterization and 571 PICC days. The median catheter life span was 14.0 days (range, 1~90 days). In 25 cases, catheters were maintained until the intended time (discharge, transfer, or death), while they were removed prematurely in six other cases (19%; 10.5/1000 PICC days). Thus, the catheter maintenance success rate was 81%. Of those six premature PICC removal cases, self-removal due to delirium occurred in four cases (13%; 7.0/1000 PICC days), and catheter-related blood stream infection and thrombosis were reported in one case, each (3%; 1.8/1000 PICC days). Complication cases totaled eight (26%; 14.1/1000 PICC days). The time to complication development ranged from two to 14 days and the median was seven days. There was no PICC complication-related death. Conclusion: Considering characteristics of terminally ill cancer patients, such as a poor general condition, vulnerability to trivial damage, and a limited period of survival, PICC could be a safe intravenous procedure.