• 핵의학기술
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• 제16권1호
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• pp.86-90
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• 2012

Rb-82를 이용한 PET 검사는 심근 관류의 임상적 평가에 중요한 역할을 한다고 알려져 있다. 그러나 PET/CT의 dead time 때문에 count value와 방사능농도 사이의 직선성이 유지되지 않는다면 데이터를 획득할 때 좌심실 입력 함수가 과대평가되어 심근관류가 과대평가될 수 있다. 본 연구에서는 리스트 모드에서 획득한 PET data에서 방사능농도에 따른 count value의 직선성을 평가하였다. Biograph 40 True Point PET/CT를 이용하여 직경 12 cm, 길이 10.5 cm의 cylindrical phantom에 F-18 333 MBq과 물 800 mL를 채우고 7반감기동안 10min frame/bed로 리스트 모드를 이용하여 획득하였다. Raw data는 OSEM (order: 4, subsets: 8)과 FBP (Gaussian filter FWHM 5 mm) 알고리즘을 이용하여 재구성하였다. Sinogram 정보에서 prompt counts, net true counts, random counts를 측정하였다. 재구성 된 phantom 영상에 ROI를 설정하여 총 계수와 background를 측정하고 background correction을 사용하여 count value를 측정하여 직선성을 평가하였다. 리스트 모드를 이용하여 sinogram에서 측정된 prompt counts는 방사능농도에 비례하여 증가하였다. 낮은 방사능농도에서 net true counts와 random counts는 방사능농도에 따라 증가하였다. 높은 방사능농도에서는 net true counts의 증가율이 점차 감소되었고, 반면에 random counts의 증가율은 증가하였다. 그리고 OSEM과 FBP 알고리즘으로 재구성된 영상에서 측정한 count value의 차이는 없었고 방사능농도에 비례하여 count value가 증가하고 직선성이 유지되었다. Biograph 40 True Point PET/CT scanner는 재구성된 영상에서 낮은 방사능농도뿐만 아니라 높은 방사능농도(~416.25 kBq/mL)에서도 측정 된 count value와 방사능농도 사이의 직선성이 유지되는 것을 보여주었다. 따라서 실험에서 사용한 PET/CT scanner는 Rb-82, N-13, O-15, F-18을 이용한 heart dynamic PET study에서데이터의 정량적 분석에 유용할 것으로 판단된다.

• Journal of Radiation Protection and Research
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• 제23권2호
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• pp.65-74
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• 1998

저 준위방사능 계측에서 가장 기본적으로 요구되는 것이 최적 측정시간의 결정이다. 최적화된 계측전략으로 측정시간을 결정하기 위하여 측정시간을 고정하는 방법, 측정값을 고정하는 방법, 시료와 자연계수율 또는 기준준위를 비교하여 측정하는 방법을 비교 검토하는 결정식을 도출하였다. 이 계측전략에서 기기에 주어진 측정조건 즉, 검출기의 효율, 측정기의 용량, 측정기의 최대 및 평균 자연계수율과 관련기준 즉, 기준준위, 검출한계 등을 만족하는 측정시간이 결정된다. 계측전략은 측정시 주어진 조건에서 방사능 존재확인과 정량분석에 대한 시료의 최적 측정시간의 결정을 편리하게 함으로써 일상의 저준위방사능 측정에 유용하게 사용될 것이다.

• Journal of Radiation Protection and Research
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• 제44권2호
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• pp.64-71
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• 2019

Background: It is very difficult to distinguish between a radioactive contamination source and background radiation from natural radionuclides in the marine environment by means of online monitoring system. The objective of this study was to investigate a statistical process for triggering abnormal level of count rate data measured from our on-line seawater radioactivity monitoring. Materials and Methods: Count rate data sets in time series were collected from 9 monitoring posts. All of the count rate data were measured every 15 minutes from the region of interest (ROI) for $^{137}Cs$ ($E_{\gamma}=661.6keV$) on the gamma-ray energy spectrum. The Shewhart ($3{\sigma}$), CUSUM, and Bayesian S-R control chart methods were evaluated and the comparative analysis of determination methods for count rate data was carried out in terms of the false positive incidence rate. All statistical algorithms were developed using R Programming by the authors. Results and Discussion: The $3{\sigma}$, CUSUM, and S-R analyses resulted in the average false positive incidence rate of $0.164{\pm}0.047%$, $0.064{\pm}0.0367%$, and $0.030{\pm}0.018%$, respectively. The S-R method has a lower value than that of the $3{\sigma}$ and CUSUM method, because the Bayesian S-R method use the information to evaluate a posterior distribution, even though the CUSUM control chart accumulate information from recent data points. As the result of comparison between net count rate and gross count rate measured in time series all the year at a monitoring post using the $3{\sigma}$ control charts, the two methods resulted in the false positive incidence rate of 0.142% and 0.219%, respectively. Conclusion: Bayesian S-R and CUSUM control charts are better suited for on-line seawater radioactivity monitoring with an count rate data in time series than $3{\sigma}$ control chart. However, it requires a continuous increasing trend to differentiate between a false positive and actual radioactive contamination. For the determination of count rate, the net count method is better than the gross count method because of relatively a small variation in the data points.

• Tuberculosis and Respiratory Diseases
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• 제80권3호
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• pp.304-310
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• 2017

Background: Chronic obstructive pulmonary disease (COPD), is a chronic inflammatory disorder. We evaluated whether white blood cell (WBC) count, is associated with the severity of COPD, independent of other inflammatory conditions, such as metabolic syndrome. Methods: The WBC counts were compared between 1227 COPD patients and 8679 non-COPD adults older than 40. The relationships between the WBC count, lung function, and symptoms score in COPD patients, were determined, using general linear regression analyses. Results: The WBC count was negatively associated with forced vital capacity (FVC, L), FVC (% predicted), forced expiry volume in one second ($FEV_1$, L), and $FEV_1$ (% predicted) in COPD patients. Additionally, the WBC count was independently associated with the quality of life measure, by EQ5D-index score. However, this relationship between WBC count, and disease severity, was not significant in current smokers, because of the confounding effect of smoking, on the WBC count. Conclusion: The WBC count is associated with current smoking status and COPD severity, and a risk factor for poor lung function, and quality of life, especially in non-currently smoking COPD patients. The WBC count can be used, as an easily measurable COPD biomarker.

• Annals of Laboratory Medicine
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• 제38권6호
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• pp.503-511
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• 2018

Background: Sampling a healthy reference population to generate reference intervals (RIs) for complete blood count (CBC) parameters is not common for pediatric and geriatric ages. We established age- and sex-specific RIs for CBC parameters across pediatric, adult, and geriatric ages using secondary data, evaluating patterns of changes in CBC parameters. Methods: The reference population comprised 804,623 health examinees (66,611 aged 3-17 years; 564,280 aged 18-59 years; 173,732 aged 60-99 years), and, we excluded 22,766 examinees after outlier testing. The CBC parameters (red blood cell [RBC], white blood cell [WBC], and platelet parameters) from 781,857 examinees were studied. We determined statistically significant partitions of age and sex, and calculated RIs according to the CLSI C28-A3 guidelines. Results: RBC parameters increased with age until adulthood and decreased with age in males, but increased before puberty and then decreased with age in females. WBC and platelet counts were the highest in early childhood and decreased with age. Sex differences in each age group were noted: WBC count was higher in males than in females during adulthood, but platelet count was higher in females than in males from puberty onwards (P <0.001). Neutrophil count was the lowest in early childhood and increased with age. Lymphocyte count decreased with age after peaking in early childhood. Eosinophil count was the highest in childhood and higher in males than in females. Monocyte count was higher in males than in females (P <0.001). Conclusions: We provide comprehensive age- and sex-specific RIs for CBC parameters, which show dynamic changes with both age and sex.

• Clinical and Experimental Pediatrics
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• 제64권1호
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• pp.31-36
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• 2021

Background: The diagnosis of esophageal varices (EV) is based on the findings of esophagogastroduodenoscopy (EGD), biopsy, and serum markers. Thus, noninvasive cost-effective tests through which high-risk EV children can be diagnosed are needed. Purpose: This cross-sectional study aimed to identify the noninvasive markers for EV in children with liver cirrhosis. Methods: A total of 98 children with liver cirrhosis were evaluated in this study. The spleen size, platelet count, serum albumin, liver function test results, and risk scores were evaluated prior to endoscopy. The endoscopic investigations aimed to identify the presence of EV and red signs, and determine varices sizes. Results: Endoscopy revealed varices in 43 subjects (43.9%). The spleen size, platelet count, international normalized ratio, aspartate aminotransferase to platelet ratio index (APRI), platelet count to spleen size ratio, and risk score differed significantly between patients with and without EV on univariate analysis; however, the logistic regression analysis showed no differences, indicating that none of these parameters were independently associated with the presence of EV. Conclusion: Platelet count, risk score, platelet count to spleen size, and APRI can be useful tools for the identification of high-risk patients with EV and might reduce the need for invasive methods like EGD.

• 천문학논총
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• 제20권1호
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• pp.109-116
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• 2005

When we measure a source signal in the presence of a background rate that has been independently measured, the usual approach is to obtain an estimate of the background rate by observing an empty part of the sky, and an estimate of the source signal plus background rate by observing the region where a source signal is expected. The source signal rate is then estimated by subtracting the background rate from the source signal plus background rate. However, when the rates or their observation times are small, this procedure can lead to negative estimates of the source signal rate, even when it should produce a positive value. By applying the Bayesian approach, we solve the problem and prove that the most probable value of source signal rate is zero when the observed total count is smaller than the expected background counts. It is also shown that the results from the conventional method is consistent with the most probable value obtained from the Bayesian approach when the source signal is large or the observation time is long enough.

• Journal of Radiation Protection and Research
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• 제43권3호
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• pp.85-96
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• 2018

Background: A variety of inorganic scintillators have been developed and improved for use in radiation detection and measurement, and in situ gamma-ray spectrometry in the environment remains an important area in nuclear safety. In order to verify the feasibility of promising scintillators in an actual environment, a performance test is necessary to identify gamma-ray peaks and calculate the radioactivity from their net count rates in peaks. Materials and Methods: Among commercially available scintillators, $LaBr_3(Ce)$ scintillators have so far shown the highest energy resolution when detecting and identifying gamma-rays. However, the intrinsic background of this scintillator type affects efficient application to the environment with a relatively low count rate. An algorithm to subtract the intrinsic background was consequently developed, and the in situ calibration factor at 1 m above ground level was calculated from Monte Carlo simulation in order to determine the radioactivity from the measured net count rate. Results and Discussion: The radioactivity of six natural radionuclides in the environment was evaluated from in situ gamma-ray spectrometry using an $LaBr_3(Ce)$ detector. The results were then compared with those of a portable high purity Ge (HPGe) detector with in situ object counting system (ISOCS) software at the same sites. In addition, the radioactive cesium in the ground of Jeju Island, South Korea, was determined with the same assumption of the source distribution between measurements using two detectors. Conclusion: Good agreement between both detectors was achieved in the in situ gamma-ray spectrometry of natural as well as artificial radionuclides in the ground. This means that an $LaBr_3(Ce)$ detector can produce reliable and stable results of radioactivity in the ground from the measured energy spectrum of incident gamma-rays at 1 m above the ground.

• Clinical and Experimental Pediatrics
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• 제62권9호
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• pp.353-359
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• 2019

Background: Researchers have shown that eosinophil peroxidase (EPO) is a relatively accurate marker of eosinophilia and eosinophil activity. However, its use as a marker of eosinophilic inflammation in nasal secretions is limited because the diagnostic cutoff values of EPO for use as a one-time test for allergic diseases such as allergic rhinitis have not been established. Purpose: To identify the correlation between nasal eosinophil count and EPO in children and adolescents with rhinitis. Methods: We recruited patients <18 years of age with rhinitis for more than 2 weeks or more than 2 episodes a year whose nasal eosinophil and EPO were measured at a single allergy clinic. The eosinophil percentage was calculated by dividing the eosinophil count by the number of total cells under light microscopy at ${\times}1,000$ magnification. EPO and protein were measured from nasal secretions. We retrospectively analyzed the correlation between nasal eosinophils and protein-corrected EPO (EPO/protein) value. Results: Of the 67 patients enrolled, 41 were male (61.2%); the mean age was $8.2{\pm}4.0years$. The median nasal eosinophil count was 1 and percentage was 1%. The median protein-corrected EPO value was $12.5ng/{\mu}g$ (range, $0-31ng/{\mu}g$). There was a statistically significant correlation between eosinophil count and percentage (P<0.001). However, the eosinophil percentage and EPO did not correlate. The eosinophil count and EPO had a statistically significant correlation (P=0.01). The EPO cutoff value examined for nasal eosinophil counts of 2, 5, 10, and 20 was $17.57ng/{\mu}g$ regardless of the reference count. The largest area under the curve value was obtained when the receiver operating characteristic curve was drawn using the eosinophil count of 2. Conclusion: Nasal eosinophil count was significantly associated with protein-corrected EPO.

• 대한전자공학회논문지SP
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• 제39권2호
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• pp.39-49
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• 2002

본 논문에서는 움직임 색상(Moving Color) 개념을 바탕으로 물체의 색상 정보와 움직임 정보의 효율적인 결합을 통해서 추적을 수행하는 MAWUPC(Motion Adaptive Weighted Unmatched Pixel Count)알고리즘을 제안하고, 이를 이용하여 일반적인 배경을 가지는 영상시퀀스에서 얼굴과 손을 추적하는 방법을 제안한다. MAWUPC 알고리즘은 색상 정보와 움직임 정보의 효과적인 결합을 수행하는 움직임 색상 개념에 관한 기존 연구인 AWUPC 알고리즘을 개선한 것으로, 추적하고자 하는 물체의 색상 정보를 이용한 색상 변환(Color Transform)과 움직임 검출을 위한 UPC(Unmatched Pixel Count) 연산, 그리고 움직임 정보를 추출하는 이산 칼만 필터(Discrete Kalman Filter)의 효과적인 결합으로 이루어진다. 제안하는 알고리즘은 일반적으로 물체들의 추적 과정에서 발생되는 가장 큰 문제인 유사한 색상을 가진 추적하고자 하는 물체들간의 겹침 문제와 물체의 추적에서 방해가 되는 복잡한 배경 문제를 해결할 수 있는 장점이 있다. 논문에서는 제안하는 알고리즘이 복잡한 배경 내에서 한 대의 카메라를 사용하여 획득된 컬러 영상을 대상으로 움직임이 있는 얼굴과 손의 추적에서 자주 발생되는 심각한 문제인 얼굴과 손, 손과 손의 겹침 문제를 잘 해결할 수 있다는 것을 실험을 통해 보인다.