• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• Investigative Magnetic Resonance Imaging
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• 제24권1호
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• pp.1-20
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• 2020

This document is the third part of the guidelines for the interpretation and post-processing of cardiac magnetic resonance (CMR) studies. These consensus recommendations have been developed by a Consensus Committee of the Korean Society of Cardiovascular Imaging (KOSCI) to standardize the requirements for image interpretation and post-processing of CMR. This third part of the recommendations describes tissue characterization modules, including perfusion, late gadolinium enhancement, and T1- and T2 mapping. Additionally, this document provides guidance for visual and quantitative assessment, consisting of "What-to-See," "How-To," and common pitfalls for the analysis of each module. The Consensus Committee hopes that this document will contribute to the standardization of image interpretation and post-processing of CMR studies.

• 한국세라믹학회지
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• 제42권9호
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• pp.637-644
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• 2005

In order to find a proper buffering material which can prohibit an unwanted interfacial reaction between anode and electrolyte of LSGM-based SOFC, we examined a gadolinium doped ceria and scandium doped zirconia as a candidate. For this examination, we investigated the microstructural and phase stability of the interface under different buffering layer conditions. According to the investigation, ceria based material induced a serious La diffusion out of the LSGM electrolyte resulted in the formation of very resistive $LaSrGa_3O_7$ phase at the interface. On the other hand zirconia based material was directly reacted with LSGM electrolyte and thus produced very resistive reaction products such as $La_2Zr_2O_7,\;Sr_2ZrO_4,\;LaSrGaO_4\;and\;LaSrGa_3O_7$. From this study we found that an improper buffering material induced the higher internal cell resistance rather than an interfacial stability.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2003년도 제27회 추계학술대회
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• pp.64-64
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• 2003

Objectives: Patient dose verification is clinically the most important parts in the treatment delivery of radiation therapy. The three dimensional(3D) reconstruction of dose distribution delivered to target volume helps to verify patient dose and determine the physical characteristics of beams used in intensity modulated radiation therapy(IMRT). We present Beam Intensity Scanner(BInS) system for the pre treatment dosimetric verification of two dimensional photon intensity. The BInS is a radiation detector with a custom made software for relative dose conversion of fluorescence signals from scintillator. Methods: This scintillator is fabricated by phosphor Gadolinium Oxysulphide and is used to produce fluorescence from the irradiation of 6MV photons on a Varian Clinac 21EX. The digitized fluoroscopic signals obtained by digital video camera will be processed by our custom made software to reproduce 3D relative dose distribution. For the intensity modulated beam(IMB), the BInS calculates absorbed dose in absolute beam fluence, which are used for the patient dose distribution. Results: Using BInS, we performed various measurements related to IMRT and found the followings: (1) The 3D dose profiles of the IMBs measured by the BInS demonstrate good agreement with radiographic film, pin type ionization chamber and Monte Carlo simulation. (2) The delivered beam intensity is altered by the mechanical and dosimetric properties of the collimating of dynamic and/or static MLC system. This is mostly due to leaf transmission, leaf penumbra, scattered photons from the round edges of leaves, and geometry of leaf. (3) The delivered dose depends on the operational detail of how to make multileaf opening. Conclusions: These phenomena result in a fluence distribution that can be substantially different from the initial and calculative intensity modulation and therefore, should be taken into account by the treatment planing for accurate dose calculations delivered to the target volume in IMRT.

• 대한의생명과학회지
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• 제11권1호
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• pp.31-36
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• 2005

To evaluate the magnetic resonance imaging and electron microscopic findings of the hyperacute stage of cerebral fat embolism in cats and the time needed for the development of vasogenic edema. Magnetic resonance imaging was performed at 30 minutes (group 1, n=9) and at 30 minutes and 1, 2, 4, and 6 hours after embolization with triolein (group 2, n= 10). As a control for group 2, the same acquisition was obtained after embolization with polyvinyl alcohol particles (group 3, n=5). Electron microscopic examination was done in all cats. In group 1, the lesions were iso- or slightly hyperintense on T2-weighted (T2W) and diffusion-weighted (DWIs) images, hypointense on the apparent diffusion coefficient (ADC) map image, and markedly enhanced on the gadolinium-enhanced T1-weighted images (Gd-T1WIs). In group 2 at 30 minutes, the lesions were similar to those in group 1. Thereafter, the lesions became more hyperintense on T2WIs and DWIs and more hypoinfense on the ADC map image. In group 3, the lesions showed mild hyperintensity on T2WIs at 6 hours but hypointensity on the ADC map image from 30 minutes, with a tendency toward a greater decrease over time. Electron microscopic findings revealed discontinuity of the capillary endothelial wall, perivascular and interstitial edema, and swelling of glial and neuronal cells in groups 1 and 2. The lesions were hyperintense on T2WIs and DWIs, hypointense on the ADC map image, and enhanced on Gd-T1WIs. On electron microscopy, the lesions showed cytotoxic and vasogenic edema with disruption of the blood-brain barrier.

• 한국콘텐츠학회논문지
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• 제17권7호
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• pp.215-221
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• 2017

본 연구는 two-point Dixon기법을 이용한 간의 지방정량화 검사 시 가돌리늄 조영제인 Gd-EOB-DTPA가 지방정량화에 어떠한 영향을 미치는지 알아보고자 하였다. 연구방법은 2016년 4월부터 동년 9월까지 two-point Dixon 기법을 이용해 간의 지방정량화 검사를 시행한 60명을, 두 그룹(정상의 간기증자 30명, 비정상의 간 지방증 환자 30명)으로 분류한 후 조영제 주입에 따른 지방분율의 변화를 비교 평가하였다. 연구 결과, 두 그룹 모두 조영제 주입 전 보다 후의 지방분율이 크게 감소(간 기증자 -33.8%, 간 지방증 환자 -47.2%)하는 것으로 나타나 Gd-EOB-DPTA가 지방정량화에 영향을 미친다는 것을 알 수 있었다. 결론적으로 two-point Dixon기법을 이용해 간 지방정량화 검사를 시행할 경우, Gd-EOB-DTPA 주입 전에 영상을 획득해야 지방분율의 변화를 최소화 할 수 있어 정확한 진단을 할 수 있다.

• 셀메드
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• 제4권2호
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• pp.12.1-12.12
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• 2014

Epinephrine is a critical drug for patients at risk for anaphylaxis. Here, we suggest moxibustion as an alternative method to reduce anaphylaxis. Moxibustion was applied to the Shimen (CV5) acupoint and found to attenuate compound 48/80-induced mortality. Capsazepine, a transient receptor potential vanilloid (TRPV) 1 antagonist, significantly improved overall survival rates compared to groups treated with moxibustion or 2-aminoethoxydiphenyl borate (an activator of TRPV1, 2, and 3). Probenecid (a TRPV2 agonist) also increased survival rate and reduced histamine levels. Survival rates increased by moxibustion and probenecid were completely inhibited by ruthenium red (a TRPV2 and 3 antagonist) and gadolinium chloride (general TRPV antagonist), respectively. Passive cutaneous anaphylaxis and ear swelling were significantly reduced by moxibustion and probenecid (p < 0.05). In cardiomyocytes, TRPV2 was over-expressed by compound 48/80 and histamine but this increased TRPV2 expression decreased to baseline with moxibustion and probenecid treatment. In addition, intracellular calcium levels increased by compound 48/80 were reduced by probenecid. Overall, these findings suggest that the reduction of anaphylaxis caused by moxibustion could represent a new mechanism of moxibustion related to the regulation of TRPV2 activation and promotion of epinephrine secretion.

• Journal of Korean Neurosurgical Society
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• 제29권5호
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• pp.623-627
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• 2000

Objective : Spontaneous lumbar epidural hematoma is a rare entity, although the precipitating factors such as anticoagulation therapy frequently precede it. The authors report four cases of surgically confirmed spontaneous epidural hematoma mimicking lumbar disc herniation. Methods : Between 1995 and 1998, four patients with spontaneous lumbar epidural hematoma were diagnosed. The clinical findings which are identical to that of acute disc herniation are included in this study. The operative findings and radiological characteristics are also included. Results : The magnetic resonance(MR) image findings demonstrated epidural lesions of intermediate to low signal intensity equivalent to those of normal discs on $T_1$-weighted images, and epidural lesions of high signal intensity higher than these normal discs on a $T_2$-weighted image. The image findings also showed rim enhanced pattern of the gadolinium-enhanced $T_1$-weighted MR images. All of the hematomas was associated with a small concomitant disc herniation or underlying annular tear. Conclusion : The authors speculate that spontaneous lumbar epidural hematoma results from tearing of the fragile penetrating vein caused by underlying disc or annulus disruption between Batson' plexus and vertebral body.

• Journal of Korean Neurosurgical Society
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• 제55권1호
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• pp.5-11
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• 2014

Objective : We evaluated pseudoprogression (PsPD) following radiation therapy combined with concurrent temozolomide (TMZ), and we assessed pseudoresponse following anti-angiogenic therapy for patients with recurrent disease using the Response Assessment of the Neuro-Oncology Working Group. Methods : Patients who were pathologically confirmed as having high-grade glioma received radiotherapy with concurrent TMZ followed by adjuvant TMZ. Bevacizumab (Avastin) with CPT-11 were used as a salvage option for cases of radiologic progression. Magnetic resonance imaging (MRI) was routinely performed 1 month after concurrent radiochemotherapy (CRT) and every 3 months thereafter. For cases treated with the bevacizumab-containing regimen for progressive disease, MRI was performed every 2 months. Results : Of 55 patients, 21 (38%) showed radiologic progression within 4 weeks after CRT. Of these patients, 16 (29%) showed progression at second post-CRT MRI (etPD) and five (9%) showed improvement (PsPD). Seven of thirty-four initially non-progressed patients showed progression at the second post-CRT MRI (ltPD). No difference in survival was observed between the etPD and ltPD groups (p=0.595). Five (50%) of ten patients showed a radiological response after salvage bevacizumab therapy. Four of those patients exhibited rapid progression immediately after discontinuation of the drug (drug holiday). Conclusion : Twelve weeks following treatment could be the optimal timing to determine PsPD or true progression. MRI with gadolinium enhancement alone is not sufficient to characterize tumor response or growth. Clinical correlation with adequate follow-up duration and histopathologic validation may be helpful in discriminating PsPD from true progression.

• Journal of Korean Neurosurgical Society
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• 제29권1호
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• pp.113-117
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• 2000

Objective : Asymptomatic cyst of the pineal gland is a common incidental finding in adults on computerized tomography or magnetic resonance image(MRI) or at postmortem examination. This study was conducted to identify MRI findings of the benign pineal cysts and to determine the proper management of asymptomatic pineal cysts. Methods : From January 1995 to March 1999, 13 cases of asymptomatic pineal cysts were diagnosed incidentally on MRI. The mean age of the patients at diagnosis was 43 years(ranged 8 to 69 years). Five patients were females and eight patients were males. We analyzed the clinical presentations and MRI findings. Results : Clincal features were not related to pineal cysts in all 13 cases included posttraumatic headache in seven cases, headache related to brain tumor in two cases, one of facial palsy, one of diabetic neuropathy, and two of other diseases. MRI demonstrated a well-demarcated mass lesion(mean 1.3cm in diameter) of low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Gadolinium-enhanced MRI, performed in 10 cases, demonstrated a rim enhancement. Hydrocephalus was not present in all cases. Follow-up MRI(ranged 12 to 36 months) obtained in 3 of the 13 patients showed stability of cyst size. After symptomatic treatment, presenting symptoms were resolved in all patients and symptom related to pineal cysts have not been developed during follow up period(mean 27 months). Conclusion : The long-term behavior of asymptomatic pineal cysts is still unknown. But we advocate conservative management of these benign pineal cysts that may be developmental variants of normal pineal gland.