• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.649-652
• /
• 1992

ECR(Electron Cyclotron Resonance) occure at ${\omega}_c$=${\omega}$, ${\omega}_c$:electron cycltron frequency, ${\omega}$:electromagnetic wave frequency. ECR system have several merit, 1) power transefer efficiency 2) low neutral gas pressure (below 1 mTorr) 3) high plasma density($10^{12}$ $cm^{-3}$). It is applicated variously in the field of semiconductor and new materials as the manufacturing equipment. Magnetic field in ECR system contruct resonance layer (${\omega}$=2.45GHz, $B_z$=875 Gauss) and control plasma. Plasma is almost generated at resonance layer. If the distance between substrate and resonance layer is short, uniformity of plasma is related with profile of resonance layer. Plasma have the property "Cold in Field", so directonality of magnetic field is one of the control factors of anisotropic etching. In this study, we calculate B field and flux line distribution, optimize geometry and submagnet current and improve of magnetic field directionality (99.9%) near substrate. For the purpose of calculation, vector potential A(r,z) and magnetic field B(r,z), green function and numerical integration is used. Object function for submagnet optimization is magnetic field directionality on the substrate and Powell method is used as optimization skim.

• Journal of Veterinary Clinics
• /
• v.34 no.5
• /
• pp.377-380
• /
• 2017

An 8-year-old, shih-tzu female dog was referred due to neurological signs including paraparesis and back pain. On the complete blood count, hematologic analysis showed elevated leukocytosis. Serum biochemical analysis revealed elevated serum alkaline phosphatase concentration and C-reactive protein concentration. On the neurologic exam, the dog was suspected to have thoracolumbar myelopathy. On magnetic resonance imaging, there were masses within the spinal canal at L1-3 intervertebral disc space that were located dorsal to spinal cord. It was hyperintense on T1-, T2-weighted magnetic resonance images, Fluid-attenuated inversion recovery, and fat suppression images. The contrast-enhanced T1-weighted images showed no enhancement. The lesions were well circumscribed. The spinal cord was compressed and displaced ventrally by the mass. After removal of the masses via L1-L3 dorsal laminectomy, pyogranulomatous inflammation was confirmed by histopathological examination. Six months after surgery, the dog recovered uneventfully and remained fully ambulatory with no neurological deficits. This case demonstrates the utility of magnetic resonance imaging for the diagnosis of spinal canal pyogranulomatous inflammation.

• Investigative Magnetic Resonance Imaging
• /
• v.14 no.1
• /
• pp.69-73
• /
• 2010

Cerebral fat embolism (CFE) is a rare, albeit potentially lethal complication of long-bone fractures. All trauma patients who are initially lucid and subsequently experience mental status deterioration should undergo immediate evaluation of possible CFE. In the present case, magnetic resonance imaging (MRI) was the most sensitive technique for the diagnosis of CFE, particularly the use of diffusionweighted images (DWI). The authors present this case to report a pathophysiologybased interpretation of the MR characteristics and treatment of CFE.

• The Korean Journal of Pain
• /
• v.6 no.2
• /
• pp.280-283
• /
• 1993

Idiopathic hyperhidrosis is a physically and emotionally distressing symptom, which lacks a precise definition. Although operative and nonoperative methods have been shown to be effective in the treatment of idiopathic hyperhidrosis, limitations, cautions and complications are inherent in their extended use. The purpose of this report is to describe the theraputetic effects of magnetic resonance for managing idiopathic hyperhidrosis. A 28 years old woman had been suffering from profuse sweating on both planter and palmar sides for 15 years. We successfully treated this symptom with the 6 magnetic resonance treatments without any complications. Now she lives well in a condition of normal sweating after the applications. It suggest that short daily periods of exposure to appropriate magnetic resonance can beneficially modulate the balance of autonomic nervous system that are responsible for sympathetic overflow, and that there is an effective window of induced electrical magnetism in which sympathetic function can be controlled in the absence of side effects.

• Journal of Electrical Engineering and Technology
• /
• v.3 no.2
• /
• pp.213-217
• /
• 2008

The flux-lock type superconducting fault current limiter(SFCL) can apply the magnetic field into the high-$T_C$ superconducting(HTSC) element by adopting the magnetic field coil in its third winding. To apply the magnetic field into the HTSC element effectively, the capacitor for LC resonance is connected in series with the magnetic field coil. However, the current waveform of third winding for the application of the magnetic field is affected by the LC resonance condition for the frequency of the source voltage and can affect the waveform of the limited fault current. In this paper, the current waveform of the third winding in the flux-lock type SFCL according to LC resonance condition during a fault period was analyzed. From the differential equation for its electrical circuit, the current equation of the third winding was derived and described with the natural frequency and the damping ratio as design parameters. Through the analysis according to the design parameters of the third winding, the waveform of the limited fault current was confirmed to be influenced by the current waveform of the third winding and the design condition for the stable fault current limiting operation of this SFCL was obtained.

• Investigative Magnetic Resonance Imaging
• /
• v.26 no.2
• /
• pp.83-95
• /
• 2022

The purpose of this study was to establish and provide guidelines for the standardized acquisition and interpretation of diffusion-weighted magnetic resonance imaging (DW-MRI) to improve the image quality and reduce the variability of the results interpretation. The standardized protocol includes the use of high-resolution DW-MRI with advanced techniques and post-processing. The aim of the protocol is to increase the effectiveness of the medical image information exchange involved in the construction, activation, and exchange of clinical information for healthcare use. An organized interpretation form could make DW-MRIs' interpretation easier and more familiar. Herein, the authors briefly review the basic principles, optimized image acquisition, standardized interpretation guidelines, false negative and false positive cases of DW-MRI, and provide a standard interpretation form and examples of various cases to help users become more familiar with the DW-MRI.

• Investigative Magnetic Resonance Imaging
• /
• v.25 no.4
• /
• pp.229-251
• /
• 2021

Arteriosclerosis is the leading cause of stroke, with a fatality rate surpassing that of ischemic heart disease. High-resolution vessel wall magnetic resonance imaging is generally recognized as a non-invasive and panoramic method for the evaluation of arterial plaque; however, this method requires improved signal-to-noise ratio and scanning speed. Recent advances in high-density head and neck coil arrays are characterized by broad coverage, multiple channels, and closefitting designs. This review analyzes fast magnetic resonance imaging from the perspective of accelerated algorithms for vessel wall imaging and demonstrates the need for effective algorithms for signal acquisition using advanced radiofrequency system. We summarize different phased-array structures under various experimental objectives and equipment conditions, introduce current research results, and propose prospective research studies in the future.

• Journal of Korean Neurosurgical Society
• /
• v.66 no.2
• /
• pp.172-182
• /
• 2023

Objective : The blood-brain barrier (BBB) is an obstacle for molecules to pass through from blood to the brain. Focused ultrasound is a new method which temporarily opens the BBB, which makes pharmaceutical delivery or removal of neurodegenerative proteins possible. This study was demonstrated to review our BBB opening procedure with magnetic resonance guided images and find specific patterns in the BBB opening. Methods : In this study, we reviewed the procedures and results of two clinical studies on BBB opening using focused ultrasound regarding its safety and clinical efficacy. Magnetic resonance images were also reviewed to discover any specific findings. Results : Two clinical trials showed clinical benefits. All clinical trials demonstrated safe BBB opening, with no specific side effects. Magnetic resonance imaging showed temporary T1 contrast enhancement in the sonication area, verifying the BBB opening. Several low-signal intensity spots were observed in the T2 susceptibility-weighted angiography images, which were also reversible and temporary. Although these spots can be considered as microbleeding, evidence suggests these are not ordinary microbleeding but an indicator for adequate BBB opening. Conclusion : Magnetic resonance images proved safe and efficient BBB opening in humans, using focused ultrasound.

• Anatomy and Cell Biology
• /
• v.56 no.4
• /
• pp.469-473
• /
• 2023

Anomalies of anterior cerebral artery (ACA) include aplasia, hypoplasia and variations in number. Magnetic resonance angiography (MRA) is a non-invasive diagnostic technique for assessment of anomalies of cerebral arteries. The aim of the study was to determine the role of MRA in detection of variants of ACA in adults. This study is an observational retrospective study. This study included forty-nine adult cases (28 males and 21 females), mean age 48±12.9 SD with anomalies of ACA in MRA. Magnetic resonance imaging of the brain and MRA were done to all patients. Cerebral MRA and magnetic resonance images were evaluated for frequency and distribution of variants of anterior cerebral arteries, associated aneurysms and infarctions. Odds ratios (ORs) and relative risk were calculated to determine risk of occurrence of cerebral infarctions in patients with anomalies of ACA. Hypoplasia of ACA was the commonest anomaly of ACA (51% of cases). Risk of occurrence of cerebral infarctions was higher in cases with azygos variant (OR, 3.3; P=0.35) than in those with hypoplastic ACA (OR, 2; P=0.58). MRA was highly reliable in identification of different variants of ACA and concomitant vascular changes.

• Journal of the Korean Magnetic Resonance Society
• /
• v.23 no.1
• /
• pp.12-19
• /
• 2019

A former study has shown that the spin-lattice relaxation time ($T_1$) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, $132{\mu}T$. To study the field dependence and the origin of the contrast we measured $T_1$ in pairs of ex-vivo prostate tissues at the Earth's magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for $T_1$ measurements at $40{\mu}T$. The $T_1$ contrast, ${\delta}=1-T_1$ (more cancer)/$T_1$(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason's score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and $T_1$ of the cancerous prostate tissues.