• Investigative Magnetic Resonance Imaging
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• 제25권1호
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• pp.47-52
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• 2021

Paraganglioma is a rare tumor of paraganglia, derived from neural crest cells in sympathetic or parasympathetic ganglions. It can be widely distributed from the skull base to the bottom of the pelvis. The pancreas, however, is a rare location of this neoplasm, and only a limited number of cases have been reported in the English literature, especially with gadoxetic-acid-enhanced magnetic resonance imaging (MRI) and diffusion-weighted images (DWI). We herein report a case of pathologically proven paraganglioma in the pancreas head with a literature review on endoscopic ultrasonography (EUS), computed tomography (CT), gadoxetic-acid-enhanced MRI, and DWI sequence.

• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 2001년도 제18회 학술발표회
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• pp.32-32
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• 2001

• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 2000년도 제17회 학술발표회
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• pp.42-42
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• 2000

• Geomechanics and Engineering
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• 제29권3호
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• pp.207-218
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• 2022

In submerged floating tunnels (SFTs), a next-generation maritime transportation infrastructure, the tunnel module floats in water due to buoyancy. For the effective and economical use of SFTs, connection with the ground is inevitable, but the stability of the shore connection is weak due to stress concentration caused by the displacement difference between the subsea bored tunnel and the SFT. The use of an elastic joint has been proposed as a solution to solve the stability problem, but it changes the dynamic characteristics of the SFT, such as natural frequency and mode shape. In this study, the finite element method (FEM) was used to simulate the elastic joints in shore connections, assuming that the ground is a hard rock without displacement. In addition, a small-scale model test was performed for FEM model validation. A parametric study was conducted on the resonance behavior such as the natural frequency change and velocity, stress, and reaction force distribution change of the SFT system by varying the joint stiffness under loading conditions of various frequencies and directions. The results indicated that the natural frequency of the SFT system increased as the stiffness of the elastic joint increased, and the risk of resonance was the highest in the low-frequency environment. Moreover, stress concentration was observed in both the SFT and the shore connection when resonance occurred in the vertical mode. The results of this study are expected to be utilized in the process of quantitative research such as designing elastic joints to prevent resonance in the future.

• Investigative Magnetic Resonance Imaging
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• 제22권4호
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• pp.218-228
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• 2018

Purpose: The objective of this study is to determine the effect of physical changes on MR temperature imaging at 7.0T and to examine proton-resonance-frequency related changes of MR phase images and T1 related changes of MR magnitude images, which are obtained for MR thermometry at various magnetic field strengths. Materials and Methods: An MR-compatible capacitive-coupled radio-frequency hyperthermia system was implemented for heating a phantom and swine muscle tissue, which can be used for both 7.0T and 3.0T MRI. To determine the effect of flip angle correction on T1-based MR thermometry, proton resonance frequency, apparent T1, actual flip angle, and T1 images were obtained. For this purpose, three types of imaging sequences are used, namely, T1-weighted fast field echo with variable flip angle method, dual repetition time method, and variable flip angle method with radio-frequency field nonuniformity correction. Results: Signal-to-noise ratio of the proton resonance frequency shift-based temperature images obtained at 7.0T was five-fold higher than that at 3.0T. The T1 value increases with increasing temperature at both 3.0T and 7.0T. However, temperature measurement using apparent T1-based MR thermometry results in bias and error because B1 varies with temperature. After correcting for the effect of B1 changes, our experimental results confirmed that the calculated T1 increases with increasing temperature both at 3.0T and 7.0T. Conclusion: This study suggests that the temperature-induced flip angle variations need to be considered for accurate temperature measurements in T1-based MR thermometry.

• Imaging Science in Dentistry
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• 제51권2호
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• pp.149-154
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• 2021

Purpose: This study aimed to investigate the computed tomography and magnetic resonance imaging features of giant cell tumors in the temporomandibular joint region to facilitate accurate diagnoses. Materials and Methods: From October 2007 to June 2020, 6 patients (2 men and 4 women) at Yonsei University Dental Hospital had histopathologically proven giant cell tumors in the temporomandibular joint. Their computed tomography and magnetic resonance imaging findings were reviewed retrospectively, and the cases were classified into 3 types based on the tumor center and growth pattern observed on the radiologic findings. Results: The age of the 6 patients ranged from 25 to 53 years. Trismus was found in 5 of the 6 cases. One case recurred. The mean size of the tumors, defined based on their greatest diameter, was 32 mm (range, 15-41 mm). The characteristic features of all cases were a heterogeneously-enhancing tumorous mass with a lobulated margin on computed tomographic images and internal multiplicity of signal intensity on T2-weighted magnetic resonance images. According to the site of origin, 3 tumors were bone-centered, 2 were soft tissue-centered, and 1 was peri-articular. Conclusion: Computed tomography and magnetic resonance imaging yielded a tripartite classification of giant cell tumors of the temporomandibular joint according to their location on imaging. This study could help clinicians in the differential diagnosis of giant cell tumors and assist in proper treatment planning for tumorous diseases of the temporomandibular joint.

• Clinics in Shoulder and Elbow
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• 제25권3호
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• pp.182-187
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• 2022

Background: This study was designed to evaluate and compare the diagnostic value of magnetic resonance imaging (MRI) and indirect magnetic resonance arthrography (I-MRA) imaging with those of arthroscopy and each other. Methods: This descriptive-analytical study was conducted in 2020. All patients who tested positive for labrum lesions during that year were included in the study. The patients underwent conservative treatment for 6 weeks. In the event of no response to conservative treatment, MRI and I-MRA imaging were conducted, and the patients underwent arthroscopy to determine their ultimate diagnosis and treatment plan. Imaging results were assessed at a 1-week interval by an experienced musculoskeletal radiologist. Image interpretation results and arthroscopy were recorded in the data collection form. Results: Overall, 35 patients comprised the study. Based on the kappa coefficient, the results indicate that the results of both imaging methods are in agreement with the arthroscopic findings, but the I-MRA consensus rate is higher than that of MRI (0.612±0.157 and 0.749±0.101 vs. 0.449±0.160 and 0.603±0.113). The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of MRI in detecting labrum tears were 77.77%, 75.00%, 91.30%, 50.00%, and 77.14%, respectively, and those of I-MRA were 88.88%, 75.00%, 92.30%, 66.66%, and 85.71%. Conclusions: Here, I-MRA showed higher diagnostic value than MRI for labral tears. Therefore, it is recommended that I-MRA be used instead of MRI if there is an indication for potential labrum lesions.

• Journal of Magnetics
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• 제9권1호
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• pp.1-4
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• 2004

Three successive phase transitions in bis-n-octhylammonium hexachlorostannate, $(n-C_8H_{17}NH_3)_2SnCl_6$, were studied by means of the ^1H nuclear magnetic resonance linewidth and spin-lattice relaxation measurements. Unlike the compounds with longer hydrocarbon chains, the order-disorder and conformational nature were found to coexist in the phase transitions.

• 소음진동
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• 제8권6호
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• pp.1144-1149
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• 1998

A two degree-of-freedom model of suspended cables is studied for forced resonant response. The method of averaging is used to obtain first-order approximations to the response of the system. A bifurcation analysis of the averaged system is performed in the case of 2-to-1 internal resonance. Nonlinear coupled-mode motions are found to bifurcate from single-mode responses and further bifurcate to limit cycle motions via Hopf bifurcations. The limit cycle solutions undergo period doubling bifurcations to chaos.

• 한국자기공명학회논문지
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• 제24권3호
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• pp.77-85
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• 2020

Stable isotope enrichment in proteins is necessary for high-resolution nuclear magnetic resonance (NMR) experiments. Although methods for ¹³C, ¹⁵N and ²H-enrichment in prokaryotic cells are well established, full processing and correct folding of complex protein systems require higher organisms as the expression host. In the present study, we review recent efforts to enrich stable isotopes in mammalian cells for protein NMR studies.