• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.75-78
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• 2003

MPEG-4 표준은 저작자가 정지영상, 텍스트, 2D/3D 그래픽스, 오디오, 심지어 임의형의 비디오 등과 같이 다양한 형태의 객체들을 개별적으로 구성하고 이들을 시/공간자적으로 다루기 용이하게 해 준다. 이와 같은 객체 기반 코딩 특성에 의해서 대화형 방송 콘텐츠를 제작하는데 가장 유용한 방식으로 고려할 수 있다. 피러나, 콘텐츠의 제작, 전송, 소비 관전에서 고려해 달 때, 콘텐츠 제작자 또는 저작권자의 보호 및 관리가 필요하게 되었다. 이에 따라 최근에는 OPIMA (Open Platform Initiative for Multimedia Access), SDMI (Secure Digital Music Initiative) and MPEG(Moving Picture Expert Group) OPIMATfMr(Intellectual Property Management & Protection)와 같은 국제 표준 단체들이 콘텐츠 보호 및 관리에 대한 관심을 가지게 되었다. 특히, MPEG의 경우에 MPEG-4 IPMP를 표준화하여 디지털 콘텐츠와 저작권에 대한 보호를 체계적이고 효과적으로 다루는 연구를 가장 활발히 해오고 있다. 이 논문에서 우리는 MPEG-4 콘텐츠 저작자가 MPEG-4 규격에 맞게 보호화 된 객체 기반 방송용 콘텐츠를 쉽고 편리하게 제작학 수 있도록 하기 위한 MPEG씨 콘텐츠 및 저자권 보호를 위한 MPEG-4 IPMP 저작 도구를 제안하고자 한다. 제안한 MPEG-4 콘텐츠 및 저작권 보호 저작 도구는 저작자에게 친근한 사용자 인터페이스를 제공하여 편집 및 수정이 용이한 텍스트 포맷인 IPMP회된 XMT(extensible Mpeg-4 Textual format) 파일을 생성한다. 또한, 콘텐츠 전송 및 저장의 효율성을 위해 이진 포멧인 IPMP화된 MP4 파일을 생성할 수 있다.으로써, 에러 이미지가 가지고 있는 엔트로피에 좀 근접하게 코딩을 할 수 있게 되었다. 이 방법은 실제로 Arithmetic Coder를 이용하는 다른 압축 방법에 그리고 적용할 수 있다. 실험 결과 압축효율은 JPEG-LS보다 약 $5\%$의 압축 성능 개선이 있었으며, CALIC과는 대등한 압축률을 보이며, 부호화/복호화 속도는 CALIC보다 우수한 것으로 나타났다.우 $23.87\%$($18.00\~30.91\%$), 갑폭 $23.99\%$($17.82\~30.48\%$), 체중 $91.51\%$($58.86\~129.14\%$)이였으며 성장율은 사육 온도구간별 차는 없었다.20 km 까지의 지점들(지점 2에서 지점 6)에서 매우 높은 값을 보이며 이는 조석작용으로 해수와 담수가 강제혼합되면서 표층퇴적물이 재부유하기 때문이라고 판단된다. 영양염류는 월별로 다소의 차이는 있으나, 대체적으로 지점 1과 2에서 가장 낮고, 상류로 갈수록 점차 증가하며 지점 7 상류역이 하류역에 비해 높은 농도이다. 월별로는 7월에 규산염, 용존무기태질소 및 암모니아의 농도가 가장 높은 반면에 용존산소포화도는 가장 낮다. 그러나 지점 14 상류역에서는 5월에 측정한 용존무기태질소, 암모니아, 인산염 및 COD 값이 7월보다 다소 높거나 비슷하다. 한편 영양염류와 COD값은 대체적으로 8월에 가장 낮으나 용존산소포화도는 가장 높다.출조건은 $100^{\circ}C$에서 1분간의 고온단시간 추출이 적합하였다. 증가를 나타내었는데, 저장기간에 따른 물성의 변화는 숭어에 비하여 붕장어가 적었다.양식산은 aspartic acid 및 proline이 많았다. 또한 잉어는 천연산이

• Journal of radiological science and technology
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• v.11 no.2
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• pp.27-64
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• 1988

Most hospital administrators in our country have doubted whether or not the size of their hospital personnel staffs, and the personnel management styles implemented are efficient or not. Actually, increased personnel expenditures due to sophisticated specialization of medical practices has become the biggest hospital expense. Therefore, it is said that hospitals can be run move efficiently by implementing reasonable management strategies for hospital personnel management. In this paper, the departments of diagnostic radiography in 16 general hospitals in Seoul, which were classified into 4 groups by the scale of hospital beds, were used as sample cases. Then, the data for the number of X-ray examination by diagnostic item was collected from sample hospitals. The unit hour spent on X-ray examinations in each diagnostic service was quoted from "A Study on setting-up of the relative value units of medical services and on the structure of current fee schedules" written by Mr. Ik Je Seong. The data analysis results are as follows; First, the number of hours per day spent on X-ray examinations in 13 hospitals out of 16 hospitals, was shorter than the general daily working hours (8 hours). Second, in the morning there was not enough time to work for X-ray examinations required, with the available manpower. In the afternoon, however, the situation was diametrically opposed to that in the morning. Third, in light of above results, though most hospitals employ sufficient personnel for the quantity of the actural work, they were always short-handed where their works were performed Fourth, this study tells us that there is a maldistribution of the work in the schedule : too much work for the available personnel in the morning. The following recommendations are resulted from the data analysis described above. First, it is recommended that all out-patients coming again, except specific patients(G. B. or I.V.P. etc) who have to have their X-ray examinations on an empty stomach in the morning among out-patients, be required to visit the hospital in the afternoon. Second, it is recommended that all new out-patients be required to make a reservation in order to equalize the number of patients throughout the day. Third, it is recommended that all in-patients, except specified patients, be arranged to have their X-ray examinations in the afternoon. Fourth, it is recommended that part time workers be employed during peak hours. This recommendation, if applied in a wider scale, would allow hospitals to overcome the problem of the maldistribution of work and personnel, and then more efficient hospital management through the appropirate personnel management procedures could be expected.

• Korean Journal of Radiology
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• v.22 no.9
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• pp.1525-1536
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• 2021

Objective: To investigate the feasibility of cine three-dimensional (3D) balanced steady-state free precession (b-SSFP) imaging combined with a non-local means (NLM) algorithm for image denoising in evaluating cardiac function in children with repaired tetralogy of Fallot (rTOF). Materials and Methods: Thirty-five patients with rTOF (mean age, 12 years; range, 7-18 years) were enrolled to undergo cardiac cine image acquisition, including two-dimensional (2D) b-SSFP, 3D b-SSFP, and 3D b-SSFP combined with NLM. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) of the two ventricles were measured and indexed by body surface index. Acquisition time and image quality were recorded and compared among the three imaging sequences. Results: 3D b-SSFP with denoising vs. 2D b-SSFP had high correlation coefficients for EDV, ESV, SV, and EF of the left (0.959-0.991; p < 0.001) as well as right (0.755-0.965; p < 0.001) ventricular metrics. The image acquisition time ± standard deviation (SD) was 25.1 ± 2.4 seconds for 3D b-SSFP compared with 277.6 ± 0.7 seconds for 2D b-SSFP, indicating a significantly shorter time with the 3D than the 2D sequence (p < 0.001). Image quality score was better with 3D b-SSFP combined with denoising than with 3D b-SSFP (mean ± SD, 3.8 ± 0.6 vs. 3.5 ± 0.6; p = 0.005). Signal-to-noise ratios for blood and myocardium as well as contrast between blood and myocardium were higher for 3D b-SSFP combined with denoising than for 3D b-SSFP (p < 0.05 for all but septal myocardium). Conclusion: The 3D b-SSFP sequence can significantly reduce acquisition time compared to the 2D b-SSFP sequence for cine imaging in the evaluation of ventricular function in children with rTOF, and its quality can be further improved by combining it with an NLM denoising method.

• Korean Journal of Radiology
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• v.22 no.8
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• pp.1253-1265
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• 2021

Objective: To investigate the prognostic value of preoperative cardiac magnetic resonance imaging (MRI) for long-term major adverse cardiac and cerebrovascular events (MACCEs) in patients undergoing tricuspid valve (TV) surgery for functional tricuspid regurgitation (TR). Materials and Methods: The preoperative cardiac MR images, New York Heart Association functional class, comorbidities, and clinical events of 78 patients (median [interquartile range], 59 [51-66.3] years, 28.2% male) who underwent TV surgery for functional TR were comprehensively reviewed. Cox proportional hazards analyses were performed to assess the associations of clinical and imaging parameters with MACCEs and all-cause mortality. Results: For the median follow-up duration of 5.4 years (interquartile range, 1.2-6.6), MACCEs and all-cause mortality were 51.3% and 23.1%, respectively. The right ventricular (RV) end-systolic volume index (ESVI) and the systolic RV mass index (RVMI) were higher in patients with MACCEs than those without them (77 vs. 68 mL/m², p = 0.048; 23.5 vs. 18.0%, p = 0.011, respectively). A high RV ESVI was associated with all-cause mortality (hazard ratio [HR] per value of 10 higher ESVI = 1.10, p = 0.03). A high RVMI was also associated with all-cause mortality (HR per increase of 5 mL/m² RVMI = 1.75, p < 0.001). After adjusting for age and sex, only RVMI remained a significant predictor of MACCEs and all-cause mortality (p < 0.05 for both). After adjusting for multiple clinical variables, RVMI remained significantly associated with all-cause mortality (p = 0.005). Conclusion: RVMI measured on preoperative cardiac MRI was an independent predictor of long-term outcomes in patients who underwent TV surgery for functional TR.

• Korean Journal of Radiology
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• v.24 no.6
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• pp.553-563
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• 2023

Objective: Functional magnetic resonance imaging (fMRI) and diffusion tensor imaging-derived tractography (DTI-t) contribute to the localization of language areas, but their accuracy remains controversial. This study aimed to investigate the diagnostic performance of preoperative fMRI and DTI-t obtained with a simultaneous multi-slice technique using intraoperative direct cortical stimulation (DCS) or corticocortical evoked potential (CCEP) as reference standards. Materials and Methods: This prospective study included 26 patients (23-74 years; male:female, 13:13) with tumors in the vicinity of Broca's area who underwent preoperative fMRI and DTI-t. A site-by-site comparison between preoperative (fMRI and DTI-t) and intraoperative language mapping (DCS or CCEP) was performed for 226 cortical sites to calculate the sensitivity and specificity of fMRI and DTI-t for mapping Broca's areas. For sites with positive signals on fMRI or DTI-t, the true-positive rate (TPR) was calculated based on the concordance and discordance between fMRI and DTI-t. Results: Among 226 cortical sites, DCS was performed in 100 sites and CCEP was performed in 166 sites. The specificities of fMRI and DTI-t ranged from 72.4% (63/87) to 96.8% (122/126), respectively. The sensitivities of fMRI (except for verb generation) and DTI-t were 69.2% (9/13) to 92.3% (12/13) with DCS as the reference standard, and 40.0% (16/40) or lower with CCEP as the reference standard. For sites with preoperative fMRI or DTI-t positivity (n = 82), the TPR was high when fMRI and DTI-t were concordant (81.2% and 100% using DCS and CCEP, respectively, as the reference standards) and low when fMRI and DTI-t were discordant (≤ 24.2%). Conclusion: fMRI and DTI-t are sensitive and specific for mapping Broca's area compared with DCS and specific but insensitive compared with CCEP. A site with a positive signal on both fMRI and DTI-t represents a high probability of being an essential language area.

• Korean Journal of Radiology
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• v.23 no.8
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• pp.811-820
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• 2022

Objective: To develop a model incorporating radiomic features and clinical factors to accurately predict acute ischemic stroke (AIS) outcomes. Materials and Methods: Data from 522 AIS patients (382 male [73.2%]; mean age ± standard deviation, 58.9 ± 11.5 years) were randomly divided into the training (n = 311) and validation cohorts (n = 211). According to the modified Rankin Scale (mRS) at 6 months after hospital discharge, prognosis was dichotomized into good (mRS ≤ 2) and poor (mRS > 2); 1310 radiomics features were extracted from diffusion-weighted imaging and apparent diffusion coefficient maps. The minimum redundancy maximum relevance algorithm and the least absolute shrinkage and selection operator logistic regression method were implemented to select the features and establish a radiomics model. Univariable and multivariable logistic regression analyses were performed to identify the clinical factors and construct a clinical model. Ultimately, a multivariable logistic regression analysis incorporating independent clinical factors and radiomics score was implemented to establish the final combined prediction model using a backward step-down selection procedure, and a clinical-radiomics nomogram was developed. The models were evaluated using calibration, receiver operating characteristic (ROC), and decision curve analyses. Results: Age, sex, stroke history, diabetes, baseline mRS, baseline National Institutes of Health Stroke Scale score, and radiomics score were independent predictors of AIS outcomes. The area under the ROC curve of the clinical-radiomics model was 0.868 (95% confidence interval, 0.825-0.910) in the training cohort and 0.890 (0.844-0.936) in the validation cohort, which was significantly larger than that of the clinical or radiomics models. The clinical radiomics nomogram was well calibrated (p > 0.05). The decision curve analysis indicated its clinical usefulness. Conclusion: The clinical-radiomics model outperformed individual clinical or radiomics models and achieved satisfactory performance in predicting AIS outcomes.

• Korean Journal of Radiology
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• v.23 no.2
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• pp.271-279
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• 2022

Objective: To compare the clinical and radiologic findings between perforated and non-perforated choledochal cysts in children. Materials and Methods: Fourteen patients (mean age ± standard deviation, 1.7 ± 1.2 years) with perforated choledochal cysts (perforated group) and 204 patients (3.6 ± 3.8 years) with non-perforated choledochal cysts (non-perforated group) were included between 2000 and 2019. All patients underwent choledochal cyst excision after ultrasound, CT, or MR cholangiopancreatography. Relevant data including demographics, clinical symptoms, laboratory findings, imaging findings, and outcomes were analyzed. Statistical differences were compared using the Mann-Whitney U test and Fisher's exact test. Results: Choledochal cyst perforation occurred only in children under the age of 4 years. Acute symptoms, including fever (p < 0.001), were more common in the perforated group than in the non-perforated group. High levels of white blood cells (p = 0.004), C-reactive protein (p < 0.001), and serum amylase (p = 0.002), and low levels of albumin (p < 0.001) were significantly associated with the perforated group. All 14 patients with perforated choledochal cysts had ascites, whereas only 16% (33/204) of patients in the non-perforated group had ascites (p < 0.001). In the subgroup of patients who had ascites, a large amount of ascites (p = 0.001), increase in the amount of ascites in a short time (p < 0.001), complex ascites (p < 0.001), and perihepatic pseudocysts (p < 0.001) were more common in the perforated group than in the non-perforated group. Conclusion: Children with perforated choledochal cysts have characteristic clinical and radiologic findings compared to those with non-perforated choledochal cysts. In young children with choledochal cysts, perforation should be differentiated in cases with acute symptoms, laboratory abnormalities, and characteristic ascites findings.

• Korean Journal of Radiology
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• v.23 no.12
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• pp.1260-1268
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• 2022

Objective: To propose standardized MRI-proton density fat fraction (PDFF) cutoff values for diagnosing hepatic steatosis, evaluated using contemporary PDFF measuring methods in a large population of healthy adults, using histologic fat fraction (HFF) as the reference standard. Materials and Methods: A retrospective search of electronic medical records between 2015 and 2018 identified 1063 adult donor candidates for liver transplantation who had undergone liver MRI and liver biopsy within a 7-day interval. Patients with a history of liver disease or significant alcohol consumption were excluded. Chemical shift imaging-based MRI (CS-MRI) PDFF and high-speed T2-corrected multi-echo MR spectroscopy (HISTO-MRS) PDFF data were obtained. By temporal splitting, the total population was divided into development and validation sets. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance of the MRI-PDFF method. Two cutoff values with sensitivity > 90% and specificity > 90% were selected to rule-out and rule-in, respectively, hepatic steatosis with reference to HFF ≥ 5% in the development set. The diagnostic performance was assessed using the validation set. Results: Of 921 final participants (624 male; mean age ± standard deviation, 31.5 ± 9.0 years), the development and validation sets comprised 497 and 424 patients, respectively. In the development set, the areas under the ROC curve for diagnosing hepatic steatosis were 0.920 for CS-MRI-PDFF and 0.915 for HISTO-MRS-PDFF. For ruling-out hepatic steatosis, the CS-MRI-PDFF cutoff was 2.3% (sensitivity, 92.4%; specificity, 63.0%) and the HISTO-MRI-PDFF cutoff was 2.6% (sensitivity, 88.8%; specificity, 70.1%). For ruling-in hepatic steatosis, the CS-MRI-PDFF cutoff was 3.5% (sensitivity, 73.5%; specificity, 88.6%) and the HISTO-MRI-PDFF cutoff was 4.0% (sensitivity, 74.7%; specificity, 90.6%). Conclusion: In a large population of healthy adults, our study suggests diagnostic thresholds for ruling-out and ruling-in hepatic steatosis defined as HFF ≥ 5% by contemporary PDFF measurement methods.

• Korean Journal of Radiology
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• v.23 no.4
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• pp.455-465
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• 2022

Objective: To compare the reproducibility and performance of quantitative metrics between ZOOMit and conventional intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in the diagnosis of early- and mid-stage Sjögren's syndrome (SS). Materials and Methods: Twenty-two patients (mean age ± standard deviation, 52.0 ± 10.8 years; male:female, 2:20) with early- or mid-stage SS and 20 healthy controls (46.9 ± 14.6 years; male:female, 7:13) were prospectively enrolled in our study. ZOOMit IVIM and conventional IVIM MRI were performed simultaneously in all individuals using a 3T scanner. Quantitative IVIM parameters - including tissue diffusivity (D), pseudodiffusion coefficient (D^*), and perfusion fraction (f) - inter- and intra-observer reproducibility in measuring these parameters, and their ability to distinguish patients with SS from healthy individuals were assessed and compared between ZOOMit IVIM and conventional IVIM methods, appropriately. MR gland nodular grade (MRG) was also examined. Results: Inter- and intra-observer reproducibility was better with ZOOMit imaging than with conventional IVIM imaging (ZOOMit vs. conventional, intraclass correlation coefficient of 0.897-0.941 vs. 0.667-0.782 for inter-observer reproducibility and 0.891-0.968 vs. 0.814-0.853 for intra-observer reproducibility). Significant differences in ZOOMit f, ZOOMit D^*, D^*, conventional D^*, and MRG between patients with SS and healthy individuals (all p < 0.05) were observed. ZOOMit D^* outperformed conventional D^* in diagnosing early- and mid-stage SS (area under receiver operating curve, 0.867 and 0.658, respectively; p = 0.002). The combination of ZOOMit D^*, MRG, and ZOOMit f as a new diagnostic index for SS, increased diagnostic area under the curve to 0.961, which was higher than that of any single parameter (all p < 0.01). Conclusion: Considering its better reproducibility and performance, ZOOMit IVIM may be preferred over conventional IVIM MRI, and may subsequently improve the ability to diagnose early- and mid-stage SS.

• Radiation Oncology Journal
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• v.19 no.2
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• pp.118-126
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• 2001

Purpose : In this study, it was investigated whether dose response relation existed or not in local radiotherapy for primary hepatocellular carcinoma. Materials and Methods : From January 1992 to March 2000, 158 patients were included in present study. Exclusion criteria included the presence of extrahepatic metastasis, liver cirrhosis of Child's class C, tumors occupying more than two thirds of the entire liver, and performance status on the ECOG scale of more than 3. Radiotherapy was given to the field including tumor with generous margin using 6, 10-MV X-ray. Mean tumor dose was $48.2{\pm}7.9\;Gy$ in daily 1.8 Gy fractions. Tumor response was based on diagnostic radiologic examinations such as CT scan, MR imaging, hepatic artery angiography at $4\~8$ weeks following completion of treatment. Statistical analysis was done to investigate the existence of dose response relationship of local radiotherapy when it was applied to the treatment of primary hepatocellular carcinoma. Results : An objective response was observed in 106 of 158 patients, giving a response rate of $67.1\%$. Statistical analysis revealed that total dose was the most significant factor in relation to tumor response when local radiotherapy was applied to the treatment of primary hepatocellular carcinoma. Only $29.2\%$ showed objective response in patients treated with dose less than 40 Gy, while $68.6\%\;and\;77.1\%$ showed major response in patients with $40\~50\;Gy$ and more than 50 Gy, respectively. Child-Pugh classification was significant factor in the development of ascites, overt radiation induced liver disease and gastroenteritis. Radiation dose was an important factor for development of radiation induced gastroduodenal ulcer. Conclusion : Present study showed the existence of dose response relationship in local radiotherapy for primary hepatocellular carcinoma. Only radiotherapy dose was a significant factor to predict the objective response. Further study is required to predict the maximal tolerance dose in consideration of liver function and non-irradiated liver volume.