• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.380-384
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• 1997

This study was performed to understand the exogenous-water-drop induced thermomechanical effect on the tooth in the free-running Er:YAG laser mode for the proper use of water as a laser energy absorber and coolant in dentistry. The ree-running Er:YAG laser was used in the dental hard tissue ablation study. A Microjet system was employed to dispense precise water drops. Ablation rate, recoil momentum, and temperature rise in the pulp cavity were measured with and without an exogenous water drop on the tooth surface. Exogenous water enhanced ablation rate in the thick tooth in which the ablation rate on the dry surface does not increase linearly but shows plateau. Optimal exogenous water volume was shifted from 2 nl to 4 nl as the laser energy was increased from 48 mJ to 145 mJ. The magnitude of the recoil momentum was increased as the volume of exogenous water increased. The results of this study suggest that we must pay attention to the recoil momentum or recoil pressure study or the optimal and safe usage of water in the dental treatment because these mechanical effects depend on the volume of exogenous water on the tooth surface.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.347.1-347.1
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• 2016

Screen printing is commonly used to form the electrode for crystalline silicon solar cells. However, it has caused high resistance and low aspect ratio, resulting in decrease of conversion efficiency. Accordingly, Ni/Cu/Ag plating method could be applied for crystalline silicon solar cells to reduce contact resistance. For Ni/Cu/Ag plating, laser ablation process is required to remove anti-reflection layers prior to the plating process, but laser ablation results in surface damage and then decrease of open-circuit voltage and cell efficiency. Another issue with plating process is ghost plating. Ghost plating occurred in the non-metallized region, resulting from pin-hole in anti-reflection layer. In this paper, we investigated the effect of Ni/Cu/Ag plating on the electrical properties, compared to screen printing method. In addition, phosphoric acid layer was spin-coated prior to laser ablation to minimize emitter damage by the laser. Phosphorous elements in phosphoric acid generated selective emitter throughout emitter layer during laser process. Then, KOH treatment was applied to remove surface damage by laser. At this step, amorphous silicon formed by laser ablation was recrystallized during firing process and remaining of amorphous silicon was removed by KOH treatment. As a result, electrical properties as Jsc, FF and efficiency were improved, but Voc was lower than screen printed solar cells because Voc was decreased due to surface damage by laser process. Accordingly, we expect that efficiency of solar cells could be improved by optimization of the process to remove surface damage.

• Korean Journal of Radiology
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• v.21 no.5
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• pp.572-581
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• 2020

Objective: To evaluate the safety, feasibility, and efficacy of microwave ablation (MWA) for the treatment of primary hyperparathyroidism (PHPT). Materials and Methods: This study enrolled 67 PHPT patients (22 men, 45 women; mean age, 56.0 ± 16.3 years; range, 18-83 years) from January 2015 to December 2018. The laboratory data, including the serum intact parathyroid hormone (iPTH), calcium, phosphorus, and alkaline phosphatase (ALP) levels, were evaluated before MWA and again 2 hours, 1 day, 7 days, 1 month, 3 months, 6 months, 12 months, 18 months, and 24 months after. Results: Complete ablation was achieved with all 72 hyperplastic parathyroid glands found on the 67 patients enrolled, 64 of whom were treated in one session and 3 were treated over two sessions. The technical success rate was 100%. The median follow-up time was 13.6 months (range, 10.0-31.1 months). The clinical success rate was 89.4%. The volume reduction rate was 79.4% at 6 months. Compared to pre-MWA, the serum iPTH, calcium, phosphorus, and ALP levels had significantly improved 6 months post-MWA (iPTH, 157.3 pg/mL vs. 39.2 pg/mL; calcium, 2.75 ± 0.25 mmol/L vs. 2.34 ± 0.15 mmol/L; phosphorus, 0.86 ± 0.20 mmol/L vs. 1.12 ± 0.22 mmol/L; ALP, 79 U/L vs. 54 U/L, respectively; all, p < 0.01). Hoarseness was a major complication in 4 patients (6.0%), but it improved spontaneously within 2-3 months. Conclusion: MWA is safe, feasible, and effective for the treatment of PHPT.

• The Journal of the Korean bone and joint tumor society
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• v.8 no.3
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• pp.83-89
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• 2002

Purpose: To analyze the postoperative functional and radiographic follow-up results in patients who underwent percutaneous radiofrequency ablation therapy after the diagnosis of osteoid osteoma. Materials and Methods: Seven patients, who were clinically and radiographically diagnosed with osteoid osteoma from July 1999 to January 2001, and received percutaneous radiofrequency ablation therapy. The average follow-up period was 15.5 months(range, 8~25 months). For the diagnosis and accurate localization of the lesion, simple radiography, computed tomography and magnetic resonance imaging(MRI) were performed preoperatively. Simple radiographs and MRI were taken periodically for the follow-up studies. Results: In all 7 patients, symptoms completely disappeared within 3 days after the operation. The average period of hospitalization was 2.4 days, excluding 1 patient who needed an additional burn treatment. The average postoperative night and day pain scores were 1.8 and 1.3, respectively. The average vocational and recreational activity scores were 1 and 0.6, respectively. Conclusions: Satisfactory functional results were obtained with percutaneous radiofrequency ablation therapy for the elimination of osteoid osteoma. Compared to conventional treatment, the advantages of this therapy were short hospitalization period, no internal fixation and bone graft for preventing fracture, and no limitation of joint motion by long fixation period.

• Korean Journal of Radiology
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• v.23 no.5
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• pp.555-565
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• 2022

Objective: To assess the efficacy and safety of ultrasound (US)-guided radiofrequency ablation (RFA) in patients with primary hyperparathyroidism (PHPT). Materials and Methods: This prospective study enrolled 39 participants (14 male, 25 female; mean age, 59.5 ± 15.3 [range, 18-87] years) between September 1, 2018, and January 31, 2021. All participants had parathyroid lesions causing PHPT, proven biochemically and through imaging. The imaging features of the PHPT nodules, including the shape, margin, size, composition, and location, were evaluated before treatment. Serum intact parathyroid hormone, calcium, and phosphorus levels; parathyroid nodule volume; and PHPT-related symptoms were recorded before and after treatment. We calculated the technical success, biochemical cure, and clinical cure rates for these patients. Complications were evaluated during and after the ablation. Results: Complete ablation was achieved in 38 of the 39 nodules in the 39 enrolled participants. All the patients were treated in one session. The technical success rate was 97.4% (38/39). The mean follow-up duration was 13.2 ± 4.6 (range, 6.0-24.9) months. At 6 and 12 months post-RFA, the biochemical cure rates were 82.1% (32/39) and 84.4% (27/32), respectively, and the clinical cure rates were 100% (39/39) and 96.9% (31/32), respectively. Only 2.6% (1/39) of the patients had recurrent PHPT. At 1, 3, 6, and 12 months after technically successful RFA, 44.7% (17/38), 34.3% (12/35), 15.8% (6/38), and 12.5% (4/32) of participants, respectively, had elevated eucalcemic parathyroid hormone levels. Recurrent laryngeal nerve paralysis occurred in 5.1% (2/39) of the patients, who recovered spontaneously within 1-3 months. Conclusion: US-guided RFA was effective and safe for PHPT patients. RFA may be an alternative treatment tool for patients who cannot tolerate or refuse to undergo surgery.

• Korean Journal of Radiology
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• v.21 no.9
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• pp.1077-1086
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• 2020

Objective: To evaluate the effect of perfluorobutane microbubbles (Sonazoid^®, GE Healthcare) on steam popping during radiofrequency (RF) ablation for treating hepatocellular carcinoma (HCC), and to assess whether popping affects treatment outcomes. Materials and Methods: The institutional review board approved this retrospective study, which included 90 consecutive patients with single HCC, who received percutaneous RF ablation as the first-line treatment. The patients were divided into two groups, based on the presence or absence of the popping phenomenon, which was defined as an audible sound with a simultaneous sudden explosion within the ablation zone as detected via ultrasonography during the procedure. The factors contributing to the popping phenomenon were identified using multivariable logistic regression analysis. Local tumor progression (LTP) and disease-free survival (DFS) were assessed using the Kaplan-Meier method with the log-rank test for performing comparisons between the two groups. Results: The overall incidence of the popping phenomenon was 25.8% (24/93). Sonazoid^® was used in 1 patient (4.2%) in the popping group (n = 24), while it was used in 15 patients (21.7%) in the non-popping group (n = 69). Multivariable analysis revealed that the use of Sonazoid^® was the only significant factor for absence of the popping phenomenon (odds ratio = 0.10, p = 0.048). There were no significant differences in cumulative LTP and DFS between the two groups (p = 0.479 and p = 0.424, respectively). Conclusion: The use of Sonazoid^® has a suppressive effect on the popping phenomenon during RF ablation in patients with HCC. However, the presence of the popping phenomenon may not affect clinical outcomes.

• Journal of Chest Surgery
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• v.47 no.3
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• pp.280-282
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• 2014

Atrial septal defect (ASD) is one of the most common congenital heart defects in adults. Surgical repair is the most common treatment approach, but device closure has recently become widely performed in accordance with the trend toward less invasive surgical approaches. Although surgery is recommended when ASD is accompanied by atrial fibrillation, this study reports a case in which a complete cure was achieved by closure of a device and totally thoracoscopic ablation.

• Journal of Chest Surgery
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• v.47 no.6
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• pp.499-503
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• 2014

Atrial fibrillation (AF) is the most common type of arrhythmia and has a large global burden. In general, treatment of AF is based on medication and consists of rate and rhythm control together with anticoagulation. However, surgical treatment may be required in patients with AF combined with organic valvular heart diseases or who experience recurrence despite medication. In addition, surgical treatment plays a role in the treatment of lone AF. This article reviews the various surgical treatment options for AF.

• Macromolecular Research
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• v.12 no.1
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• pp.134-140
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• 2004

Semi-crystalline poly(ethylene terephthalate) (PET) film surfaces were modified with argon and oxygen plasmas by radio-frequency (RF) glow discharge at 240 mTorr/40 W; the changes in topography and surface structure were investigated by atomic force microscopy (AFM) in conjunction with specular reflectance of infrared microspectroscopy (IMS). Under our operating conditions, analysis of the AFM images revealed that longer plasma treatment results in significant ablation on the film surface with increasing roughness, regardless of the kind of plasma used. The basic topographies, however, were different depending upon the kind of gas used. The specular reflectance analysis showed that the ablative mechanisms of the argon and oxygen plasma treatments are entirely different with one another. For the Ar-plasma-treated PET surface, no observable difference in the chemical structure was observed before and after plasma treatment. On the other hand, the oxygen-plasma-treated PET surface displays a significant decrease in the number of aliphatic C-H groups. We conclude that a constant removal of material from the PET surface occurs when using the Ar-plasma, whereas preferential etching of aliphatic C-H groups, with respect to, e.g. , carbonyl and ether groups, occurs upon oxygen plasma.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.14
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• pp.5799-5804
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• 2014

Background: Radiofrequency ablation (RFA) is the most widely used and studied method internationally for the local treatment of liver tumors. However, the extension of coagulation necrosis in one RFA procedure is limited and incomplete coverage of the damaged area can lead to a high local recurrence rate. Objective: In this study, we compared the effects of different solutions in enhancing hepatic radiofrequency by establishing a rabbit VX2 liver cancer model. We also determined the optimal solution to maximise effects on the extent of RFA-induced coagulation necrosis. Methods: Thirty VX2 tumor rabbits were randomly assigned to five groups: group A, RFA alone; group B, RFA with anhydrous ethanol injection; group C, RFA with 5% hypertonic saline injection; group D, RFA with lidocaine injection; and group E, RFA with a mixed solution. Routine ultrasound examinations and contrast-enhanced ultrasound (CEUS) of the ablation areas were performed after RFA. Then, we measured the major axis and transverse diameter and compared the areas of coagulation necrosis induced by RFA. Results: The mean ablation area range increased in groups B, C and especially E, and the scopes were greater compared with group A. Preoperative application of anhydrous ethanol, hypertonic saline, lidocaine and the mixed solution (groups B, C, D and E, respectively) resulted in larger coagulation necrosis areas than in group A (p<0.05). Among the groups, the coagulation necrosis areas in group E was largest, and the difference was statistically significant compared with other groups (p<0.05). Pathological findings were consistent with imaging results. Conclusions: A mixture of dehydrated alcohol, hypertonic saline and lidocaine injected with RFA increases the extent of coagulation necrosis in the liver with a single application, and the mixed solution is more effective than any other injection alone.