• 전력전자학회논문지
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• 제4권1호
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• pp.19-25
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• 1999

본 연구는 새로운 영전압, 영전류 스위칭 Forward 컨버터에 관한 것으로 종래의 하드 스위칭(Hard-Switching) Forward 컨버터에 있어서 Turn-off 및 Turn-off시 발생되는 스위칭 손실 및 출력 다이오드 역회복 특성에 따른 손실증가와 스위칭시 발생되는 기생진동을 Forward 컨버터에 있어서 1차측 주 스위칭소자 및 2차측 출력 정류다이오드와 병렬로 무손실 스너버를 적용함으로써 Forward 컨버터의 1차측 스위칭 소자의 Turn-off 및 Turn-on시 영전압, 영전류 스위칭을 이룰 수 있고, 출력 정류다이오드도 영전압, 영전류 스위칭 됨으로 다이오드의 역회복손실 및 기생 진동에 따른 EMI(Electro-Magnetic Interference)를 줄일 수 있는 무손실 스너버 적용 영전압, 영전류 스위칭 Forward 컨버터에 관한 것이다.

• Progress in Superconductivity
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• 제5권1호
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• pp.26-30
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• 2003

Magneto-cardiogram(MCG) signals may be highly distorted by the environmental noise, such as power-line interference, broadband white noise, surrounding magnetic noise, and baseline wondering. Several kinds of digital filters and noise cancellation methods have been designed and realized by many researchers, but these methods gave some problems that the original signal may be distorted by digital filter due to the wideband characteristics of background noise. To eliminate noise effectively without distortion of MCG signals, we performed multi-level frequency decomposition using wavelet packets and local adaptive noise cancellation in each local frequency range. In addition to the proposed wavelet filter to eliminate these various non-stationary noise elements, the local adaptive filter using the least mean square(LMS) algorithm and the soft threshold do-noising method are introduced in this paper. The signal to noise ratio(SNR) and the reconstruction square error(RSE) are calculated to evaluate the performance of the proposed method and compared with the results of the conventional wavelet filter and adaptive filter. The experimental results show that the proposed local adaptive filtering method is better than the conventional methods.

• Clinics in Shoulder and Elbow
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• 제23권1호
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• pp.37-40
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• 2020

Heterotopic ossification is formation of bone in atypical extra-skeletal tissues and usually occurs spontaneously or following neurologic injury with unknown cause. We report a 46-year-old female with right shoulder pain and restricted range of motion (ROM) for 3 months without history of trauma. Magnetic resonance imaging (MRI) showed a lesion within the rotator cuff supraglenoid. Excisional biopsy from a previous institution revealed a heterotopic ossificans (HO). Following repeat MRI and bone scan, histopathology from arthroscopic resection confirmed an HO. The patient demonstrated improved pain and ROM at follow-up. Idiopathic HO rarely occurs in the shoulder joint, and resection of HO should be delayed until maturation of the lesion to avoid recurrence. The current case showed that arthroscopic HO resection provides an excellent surgical view to ensure complete lesion removal and minimize soft tissue damage at the supraglenoid area. Furthermore, the minimally invasive procedure of arthroscopy may reduce rehabilitation time and facilitate early return to work.

• Journal of Korean Neurosurgical Society
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• 제45권2호
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• pp.107-111
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• 2009

Meningiomas are usually benign neoplasms in which extracranial metastases occur very rarely. We report a case of multiple extracranial metastases of an atypical meningioma following a local recurrence. A 68-year-old man presented with left-side motor weakness and dysarthria for two weeks. A computed tomography (CT) scan and magnetic resonance imaging (MRI) showed an intraventricular tumor. We performed a total mass removal, and the histopathologic findings were consistent with benign meningioma. Eight months later, the meningioma recurred. We performed a reoperation and whole brain radiation therapy postoperatively. The histopathologic findings showed atypical meningioma. Six months later, CT and MRI revealed metastases to multiple vertebrae, lung, ribs and perirenal soft tissue so a decompressive laminectomy with mass removal was performed. The histopathologic findings of the spinal tumors showed atypical meningioma. The results from perirenal biopsies were consistent with metastatic meningioma. In conclusion, extracranial metastasis as well as local recurrence must be considered in atypical or anaplastic meningioma. There must be regular follow-ups. Finally, an evaluation of the chest, abdomen and bone is necessary, especially when related symptoms or signs develop.

• Journal of Korean Neurosurgical Society
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• 제48권3호
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• pp.276-280
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• 2010

Liposarcomas are malignant tumors of the soft tissue, with myxoid liposarcoma being the second most common subtype, tending to occur in the limbs, particularly in the thighs. Myxoid liposarcomas have an intermediate prognosis between well-differentiated and pleomorphic tumors. Spinal metastasis is usual but intradural involvement is extremely rare. We present an unusual case of a multicentric myxoid liposarcoma with intradural involvement. A 41-year-old woman complained of tingling sensation on her left arm. Radiological evaluation revealed multiple masses in her cervical spine, abdominal wall, liver, heart and right thigh, all of which were resected. She was histologically diagnosed with small round cell myxoid sarcoma and underwent adjuvant chemotherapy. However, magnetic resonance imaging analysis after 1 year revealed a large metastatic mass with bony invasion at the C6-T1 level. This mass consisted of extradural and intradural components causing severe compression of the spinal cord. She underwent resection via a posterior facetectomy of C6-7 and an anterior C7 corpectomy. However, the patient died of multiple metastases 18 months after the first diagnosis.

• 대한두개안면성형외과학회지
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• 제21권1호
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• pp.69-72
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• 2020

Hemangioma is a benign vascular tumor that grows by endothelial cell hyperplasia. It occurs most frequently in the head and neck region. Nose reconstruction is tricky because of its unique three-dimensional structure and different tissue components. We report a case of successful reconstruction of near-total nose defect using the paramedian forehead flap combined with a nasolabial flap, immediately after excision of nasal hemangioma. A 49-year-old male patient was presented with a huge mass at the nose. Preoperative magnetic resonance imaging showed prominent vascular channels extending to the forehead and cheek. Complete resection of the mass was performed, which resulted in an eccentric defect. The right paramedian forehead flap and the left nasolabial flap were designed and transferred to the defect. Flap division was performed 1 month later. The patient is satisfied with the overall appearance and did not develop any functional deficit.

• Asian Pacific Journal of Cancer Prevention
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• 제13권5호
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• pp.1713-1718
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• 2012

Advanced imaging approaches (computed tomography, CT; magnetic resonance imaging, MRI; $^{18}F$-fluorodeoxyglucose positron emission tomography, FDG PET) have increased roles in cervical cancer staging and management. The recent FIGO (International Federation of Gynecology and Obstetrics) recommendations encouraged applications to assess the clinical extension of tumors rather than relying on clinical examinations and traditional non-cross sectional investigations. MRI appears to be better than CT for primary tumors and adjacent soft tissue involvement in the pelvis. FDG-PET/CT has increased in usage with a particular benefit for whole body evaluation of tumor metabolic activity. The potential benefits of advanced imaging are assisting selection of treatment based upon actual disease extent, to adequately treat a tumor with minimal normal tissue complications, and to predict the treatment outcomes. Furthermore, sophisticated external radiation treatment and brachytherapy absolutely require advanced imaging for target localization and radiation dose calculation.

• Journal of Korean Neurosurgical Society
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• 제46권2호
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• pp.156-160
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• 2009

Solitary extramedullary plasmacytomas are isolated plasma cell tumors of soft tissue that typically do not metastasize. They are rare and account for 4% of all plasma cell tumors. To our knowledge, only 14 cases of solitary extramedullary plasmacytomas in the sphenoid sinus have been reported. A 32-year-old man presented to our department with complaint of ocular pain in the right eyeball and diplopia. Physical and neurological examinations revealed intact and prompt direct and indirect light reflexes in both pupils and limitation of extraocular muscle movement seen with the lateral gaze of the right eyeball. Magnetic resonance imaging suggested the presence of mucocele or mycetoma, therefore surgical resection was performed with endoscopic endonasal transsphenoidal approach. Histopathology was consistent with plasmacytoma. Systemic work-up did not show any evidence of metastasis and the sphenoid sinus was the sole tumor site, and therefore the diagnosis of solitary extramedullary plasmacytoma was confirmed. We report a rare case of solitary extramedullary plasmacytoma in the sphenoid sinus with successful treatment using the endoscopic endonasal transsphenoidal resection and adjuvant radiotherapy.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제29권3호
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• pp.211-216
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• 2007

Temporomandibular joint disorders (TMD) often show muscular disorder, internal derangement and degenerative change of articular surface of the condyle. It is important to choose adequate diagnostic method for obtaining data for the diagnosis and treatment. Magnetic Resonance Imaging (MRI) has some advantages, because it shows good resolution image for the soft tissue and it is not invasive to the human body. We have performed serial research about the retrodiscal tissue of the TMJ according to the progress of the disease, using T2 weighted image, since 2002. In this study, we applicated resized observation area to compare signal intensity between the retrodiscal tissue of the TMJ and cerebral gray matter, using T2 weighted image.

• Journal of Korean Neurosurgical Society
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• 제50권5호
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• pp.468-471
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• 2011

Mesenchymal chondrosarcomas are rare malignant tumors of the bone and soft tissue. Spinal mesenchymal chondrosarcomas are even rarer and, to the best of our knowledge those that are concomitantly located in the intradural and extradural regions, have never been reported. We report a case of a 25-year-old man with back pain and bilateral progressive weakness of the lower extremities. Magnetic resonance imaging revealed a markedly enhanced dumbbell-shaped mass at the T7 level. The lesion was intradurally located at the left side of the spinal cord, and extended extradurally to the extraforminal space through the T7-8 intervertebral foramen. The tumor was completely excised through a posterior approach. Microscopic examination and immunohistochemical studies confirmed mesenchymal chondrosarcoma. Postoperative radiation therapy and chemotherapy were also performed to prevent local recurrence and metastasis. The patient has been symptom-free for two years after surgery. Herein, we reviewed and discussed the clinical characteristics, treatments, and outcomes of primary intraspinal mesenchymal chondrosarcomas in the literature.