• Korean Journal of Radiology
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• 제20권4호
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• pp.580-588
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• 2019

Objective: To evaluate the impact of energy and access methods on extrahepatic tumor spreading and the ablation zone in an ex vivo subcapsular tumor mimic model with a risk of extrahepatic tumor spreading. Materials and Methods: Forty-two tumor-mimics were created in bovine liver blocks by injecting a mixture of iodine contrast material just below the liver capsule. Radiofrequency (RF) ablations were performed using an electrode placed parallel or perpendicular to hepatic surface through the tumor mimic with low- and high-power protocols (groups 1 and 2, respectively). Computed tomography (CT) scans were performed before and after ablation. The presence of contrast leak on the hepatic surface on CT, size of ablation zone, and timing of the first roll-off and popping sound were compared between the groups. Results: With parallel access, one contrast leak in group 1 (1/10, 10%) and nine in group 2 (9/10, 90%) (p < 0.001) were identified on post-ablation CT. With perpendicular access, six contrast leaks were identified in each group (6/11, 54.5%). The first roll-off and popping sound were significantly delayed in group 1 irrespective of the access method (p = 0.002). No statistical difference in the size of the ablation zone of the liver specimen was observed between the two groups (p = 0.247). Conclusion: Low-power RF ablation with parallel access is proposed to be effective and safe from extrahepatic tumor spreading in RF ablation of a solid hepatic tumor in the subcapsular location. Perpendicular placement of an electrode to the capsule is associated with a risk of extrahepatic tumor spreading regardless of the power applied.

• Korean Journal of Radiology
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• 제2권3호
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• pp.151-158
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• 2001

Objective: To determine the ability of MR imaging to detect the pathological changes occurring in radiofrequency (RF) thermal lesions and to assess its accuracy in revealing the extent of tissue necrosis. Materials and Methods: Using an RF electrode, thermal lesions were created in the livers of 18 rabbits. The procedure involved three phases. In the acute phase, six animals were killed the day after performing thermal ablation with RF energy, and two on day 3. In the subacute and chronic phases, eight rabbits underwent percutaneous hepatic RF ablation. After performing MR imaging, two animals were sacrificed at 1, 2, 4, and 7 weeks after the procedure, and MRpathologic correlation was performed. Results: In the acute phase, the thermal ablation lesions appeared at gross examination as well-circumscribed, necrotic areas, representing early change in the coagulative necrosis seen at microscopic examination. They were hypointense on T2-weighted images, and hyperintense on T1-weighted images. Gadolinium-enhanced MR imaging showed that a thin hyperemic rim surrounded the central coagulative necrosis. In the subacute phase, ablated lesions also showed extensive coagulative necrosis and marked inflammation at microscopic examination. Beyond two weeks, the lesions showed gradual resorption of the necrotic area, with a peripheral fibrovascular rim. The size of lesions measured by MR imaging correlated well with the findings at gross pathologic examination. Conclusion: MR imaging effectively demonstrates the histopathological tissue change occurring after thermal ablation, and accurately determines the extent of the target area.

• Radiation Oncology Journal
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• 제9권1호
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• pp.27-35
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• 1991

8MHz 라디오파를 이용한 자입식 온열치료를 위한 기초실험의 일환으로 조직등가물을 이용하여 다양한 needle electrode의 배열을 통한 적정 온도분포를 규명하고자 하였고, 직접 개의 뇌실질에 자입 온열요법을 시도하여 이에 따른 조직 병리학적 소견을 관찰하고자 하였다. 조직등가물 실침에서 저자들은 needle electrode 1 cm 간격의 정방형 배치에서 횡단면상 $90\%$ relative SAR 분포가 약 1.25 cm 반경의 균일한 원형으로 관찰됨을 알 수 있었고 종단면상 needle electrode의 길이에 따라 균일한 온도분포가 이루어짐을 관찰할 수 있었다. 정상 개의 뇌실질에 자입하여 직접 정방형의 중심을 $43^{\circ}C$로 유지하며 50분간 온열요법을 시행한 후 관찰한 조직 병리학적 소견은 liquefactive necrosis, pyknosis of neuronal element 및 Polymorphonuclear leukocytes들이 회백질에서 급성기에 관찰 되었고 liquefactive necrosis 주위에 lipid-laden macrophage들이 관찰됨이 공통적인 특징 이었으며 후기 변화로 괴사조직 주위로 신경교세포의 증식이 관찰되었다.

• 대한영상의학회지
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• 제85권3호
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• pp.618-630
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• 2024

목적 본 연구는 낭성 및 고형성 혼합 갑상선 결절 치료에서 고주파 절제술 단독요법과 에탄올 절제 후 고주파 절제술 요법의 유효성 및 안전성을 비교하고자 하였다. 대상과 방법 본 연구는 초음파 유도 하 조직검사에서 양성으로 확인된 243개의 낭성 및 고형성 혼합 갑상선 결절을 대상으로 진행됐으며, 243개의 결절은 243명의 환자로부터 진단되었다. 연구 대상이 된 결절들은 고주파 절제술 단독요법과 에탄올 절제 후 고주파 절제술 요법을 받은 군의 두 군으로 나누어 분류됐다. 본 연구는 각 군에서의 시술 후 부피 감소율, 치료 성공률, 증상 및 미용 문제의 개선 정도를 평가하였다. 또한 시술 후 연관된 합병증이나 부작용이 발생하였는지 확인하였다. 결과 고주파 절제술 단독 요법 군에는 204명의 환자가 포함되었고, 에탄올 절제 후 고주파 절제술 요법 군에는 39명의 환자가 포함되었다. 단독요법군과 혼합요법 군에서 최종 추적 검사 시 평균 부피 감소율은 각각 81.6%와 87.2%였다. 두 군에서의 장기적 치료 성공률은 각각 90.2%와 97.4%였다. 치료 결과는 마지막 추적 관찰 시기에서 두 군에서 유사하게 나타났다. 대부분 낭성 결절에 국한된 추가 분석에서도 두 군 간에 치료 효과에 있어 유의미한 차이가 없었다. 증상 및 미용적 문제는 두 군에서 모두 현저하게 개선되었다. 시술 후 연관된 큰 합병증은 두 군 모두에서 발생하지 않았다. 결론 에탄올 절제 후 고주파 절제술 혼합 요법이 고주파 절제술 단독요법에 비해 약간 더 나은 치료 방법이지만, 두 치료 요법 모두 낭성 및 고형성 혼합 결절의 치료에 안전하고 효과적인 방법이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.1309-1312
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• 1987

Hyperthermia for the treatment of cancer has been introduced for a long time and the biological effect for the use of hyperthermia to malignant tumors has been well established and encouraging clinical results has been observed. Unfortunately, the engineering or technical aspects of hyperthermia for the deep seated tumors has not been satisfactory. We have researched and developed the radiofrequency capacitive hyperthermia system (GHT- RF8). It was composed with 8-9 MHZ RF generator, capacitive electrode, matching system, cooling system, temperature measuring system and control computer. The thermal profile was investigated in agar phantom, animals and in human tumors, which was heated with capacitive RF device.

• Current Optics and Photonics
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• 제2권1호
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• pp.53-58
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• 2018

A novel X-band high speed frequency sweep signal generator based on a tunable optoelectronic oscillator (OEO) incorporating a frequency-swept laser is presented and the theoretical fundamentals of the design are explained. A prototype of the generator with tuning range from 8.8552 GHz to 10.3992 GHz and a fine step about 8 MHz is achieved. The generated radiofrequency signal with a single sideband (SSB) phase noise lower than -100 dBc/Hz@10KHz is experimentally demonstrated within the whole tunable range, without any narrow RF band-pass filters in the loop. And the tuning speed of the frequency sweep signal generator can reach to over 1 GHz/s benefiting from applying a novel dispersion compensation modular instead of several tens of kilometers of optical fiber delay line in the system.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.262-265
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• 2003

Radiofrequency thermal ablation (RTA) as one of the microwave hyperthermia is becoming the treatment of choice for small but inoperable tumors of the liver. In this paper, we designed the applicator composed of semi-rigid coaxial cable antenna with a ring slot for RTA. To optimize the maximum output of radiation at 2450 MHz, we simulated the antenna using Electromagnetic simulation tools Maxwell program and analyzed the return loss and the electric field $E_{tot}$ at the near-field region between the simulation results and measurement results. As a result, we obtained the return loss of -29.786 dB at 2450 MHz when the antenna was placed between two blocks of a pig's liver, and the measurement results agreed with the simulation results well. Therefore, this semi-rigid coaxial cable antenna with a ring slot can be used very usefully as the applicator for RTA.r RTA.A.

• Transactions on Electrical and Electronic Materials
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• 제8권5호
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• pp.211-214
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• 2007

Chemical and morphological changes of phenol formaldehyde-based photoresist after $O_2$ radiofrequency(RF) plasma treatment depending on exposure time and source power were investigated. It was found that etch rate of photoresist sharply increased after discharge turn on and reached a limit with increase in plasma exposure time. Contact angle measurements and X-ray photoelectron spectroscopy(XPS) analysis showed that the surface chemical structure become nearly constant after 15 sec of the treatment. Atomic force microprobe(AFM) measurements were shown that surface roughness was increased with plasma exposure time.

• Journal of Korean Neurosurgical Society
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• 제60권3호
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• pp.294-300
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• 2017

Hypothalamic hamartoma (HH) is a benign indolent lesion despite the presentation of refractory epilepsy. Behavioral disturbances and endocrine problems are additional critical symptoms that arise along with HHs. Due to its nature of generating epileptiform discharge and spreading to cortical region, various management strategies have been proposed and combined. Surgical approaches with open craniotomy or endoscopy, stereotactic approaches with radiosurgery and gamma knife surgery or radiofrequency thermos-coagulation, and laser ablation have been introduced. Topographical dimension and the surgeon's preference are key factors for treatment modalities. Endoscopic disconnection has been one of the most favorable options performed in treating HHs. Here we discuss presurgical evaluation, patient selection, surgical procedures, and complications.

• Journal of Chest Surgery
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• 제27권3호
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• pp.230-233
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• 1994

A 21-year-old man with atrioventricular[AV] reentry tachycardia secondary to concealed accessory AV connection underwent surgical division of two accessory pathways following failure of radiofrequency catheter ablation. pathways were located in the left free wall area.Before cardiopulmonary bypass, the epicardial mapping confirmed the existence and localization of two accessory pathways. The patient was approached through a left atriotomy with a dissection of the left free wall area beginning with an internal mapping was carried out after separation from cardiopulmonary bypass to confirm the absence of retrograde conduction of accessory pathway. Five weeks after surgery, the electrophysiololgic study demonstrated no retrograde conduction through two accessory pathways.