• Journal of the Korean Society for Precision Engineering
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• v.23 no.3 s.180
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• pp.195-202
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• 2006

The degenerative lumbar spinal stenosis (DLSS) is a disease inducing low back pain, leg pain, convulsion. numbness, and neurogenic claudication from compression of nerve root. Intervertebra fixation was reported to increase the degeneration of neighbor lesion after treatment. Recently, a new surgical technique of inserting a fixator between interspinous processes has been introduced. The purpose of this study is to design the interspinous process fixator with flexibility to complement the trouble of using fixator in DLSS. This study evaluated the existing fixator through the mechanical test and modified it using the finite element analysis (FEA). The evaluation was based on the displacement, stiffness and von-Mises stress obtained from the mechanical test and calculated from the FEA in the biomechanical loading condition. Effects of variation in length and thickness were investigated to design an optimal fixator. Three prototypes were manufactured using FEA results. Mechanical tests under the biomechanical loading condition were performed to select the best one from these three. The selected fixator increased flexiblity by 32.9%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.1 s.256
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• pp.21-28
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• 2007

The use of drug-eluting stents has dramatically reduced the incidence of restenosis however, much remains to be teamed about the performance of these stouts. In the present study, we tested the hypothesis that the design of drug-eluting stents influences the efficacy of local drug delivery to the arterial wall and that this effect depends on both arterial geometry and the prevailing flow conditions. We performed computational simulations in which the coupled Navier-Stokes and advection-diffusion equations were solved to determine the flow field and drug concentration in the vicinity of model drug-eluting stouts It is found that the characteristics of flow phenomena can be influenced greatly by the ratio of stent diameter to vessel diameter. The presence of drug-eluting stent may have profound effect on wall shear stresses, recirculation sizes and drug distributions. The results show that recirculation zone is influenced by the imposed flow conditions and stent diameter. In pulsatile flow, the low wall shear stress and high drug concentration occur along the arterial wall during the decelerating flow conditions. These results could provide the guideline for future drug-eluting stent designs toward reducing restenosis by affecting local wall shear stress distributions associated with neointimal hyperplasia.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1509-1517
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• 2006

The intervertebral fusion was reported to increase the degeneration of the neighboring region. Recently, a new technique of inserting an interspinous process fixator has been introduced to minimize the degenerative change in the lumbar spine. This study analyzed biomechanical effects of the fixator in the lumbar spine, and designed a new prototype to improve flexibility of the fixator with a reduced size. The evaluation was based on the displacement, stiffness and von-Mises stress obtained from the mechanical test and finite element analysis. A finite element lumbar model of L1 to L5 was constructed. The finite element model was used to analyze intervertebral fusion, insertion of a commercial fixator and a new prototype. The range of motion of intervertebral segments and pressures at vertebral discs were calculated from FEA. The results showed that the stiffness of the prototype was reduced by 32.9% than that of the commercial one.

• Journal of Chest Surgery
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• v.39 no.4 s.261
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• pp.275-280
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• 2006

Background: Aortopulmonary window (APW) is a very rare congenital heart anomaly, often associated with other cardiac anomalies. It causes a significant systemic to pulmonary artery shunt, which requires early surgical correction. Accurate diagnosis and surgical correction will bring good outcomes. The purpose of this study was to describe our 20-year experience of aortopulmonary window. Material and Method: Between March 1985 and January 2005, 16 patients with APW underwent surgical repair. Mean age at operation was $157.8{\pm}245.3$ ($15.0{\sim}994.0$) days and mean weight was $4.8{\pm}2.5$ ($1.7{\sim}10.7$) kg. Patent ductus arteriosus (8), atrial septal defect (7), interruptedaortic arch (5), ventricular septal defect (4), patent foramen ovate (3), tricuspid valve regurgitation (3), mitral valve regurgitation (2), aortic valve regurgitation (1), coarctation of aorta (1), left superior vena cavae (1), and dextrocardia (1) were associated. Repair methods included 1) division of the APW with primary closure or patch closure of aorta and pulmonary artery primary closure or patch closure (11) and 2) intra-arterial patch closure (3). 3) Division of the window and descending aorta to APW anastomosis (2) in the patients with interrupted aortic arch or coarctation. Result: There was one death. The patient had 2.5 cm long severe tracheal stenosis from carina with tracheal bronchus supplying right upper lobe. The patient died at 5th post operative day due to massive tracheal bleeding. Patients with complex aortopulmonary window had longer intensive care unit and hospital stay and showed more morbidities and higher reoperation rates. 5 patients had reoperations due to left pulmonary artery stenosis (4), right pulmonary artery stenosis (2), and main pulmonary artery stenosis (1). The mean follow-up period was $6.8{\pm}5.6$ (57.0 days$\sim$16.7 years)years and all patients belonged to NYHA class 1. Conclusion: With early and prompt correction of APW, excellent surgical outcome can be expected. However, optimal surgical method needs to be established to decrease the rate of stenosis of pulmonary arteries.

• Journal of Chest Surgery
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• v.29 no.12
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• pp.1366-1372
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• 1996

Bronchoplasty has gained popularity in the selected cAses of bronchogenic carcinoma with poor pulmonary reserve, and also has been a choice of treatment for obstructive bronchial diseases since it can cure patient completely with preservation of pulmonary function. From Apr. 1990 to hpr. 19'96 two methods of bronchoplastic procedures, d patch dilating bronchoplasty and a segmental bronchial resection with end-to-end anastomosis, were performed with or without concominant pulmonary resection in 13 patients with benign bronchial stenosis and obstruction. The patients were 8 men and 5 women with average age of 43years(range 19 to 64 years). Patch dilating bronchoplasty using autogenous perichondrium and pericardium was applied in 5 cases of bronchial stenosis. Antecedan diseases of bronchial stenosls were 3 inflammatory bronchiectas is, and 2 endobronchial tuberculose is mixed with bronchi,ectas is. Segmental bronchial resection with end-to-end anastomosis was applied in 8 cases of bronchial obstruction, which were caused by endobronchial tuberculosis in 6 and cicatrization after trauma and foreign body in one case each. Bronchial obstructive symptoms and signs including recurrent pulmonary infection, dyspnea and wheezing were disappeared postoperatively with satisfactory recovery of physical activity. There was no operative mortality. Morbidity occured in 2 patients which were one case of unstability of applied bronchial patch resulting atelectasis and one case of bronchial restenosis at the anastomotic site. Based upon our experiences, we conclude that bronchoplastic procedure can be done with great success in patients with lung atelectasis caused by bronchial obstruction or stenosis and it restores physiologic function of collapsed lung with acc ptable complication.

• Progress in Medical Physics
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• v.10 no.3
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• pp.151-157
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• 1999

The GafChromic film was used for the dosimetry of a balloon angio catheter filled with the radioisotope HO-166 for endovascular irradiation. The balloon angio catheter was 2 cm long and 3 mm in diameter when inflated. The isotope, Ho-166, was produced by the neutron bombardment using the research reactor in Korea Atomic Energy Research Insititute. Co-60 teletherapy beam was used for making H-D curve for the Gaf-Chromic film. The film dosimetry was measured with a videodensitometer. The radial dose distribution indicated that the absorbed dose dropped to about 20% of the surface dose at the 1 mm away from the balloon surface and at 5 mm position the dose decreased to below 1% of the surface dose. The result also shows that with the specific activity of Ho-l66, 250 mCi/ml it takes 230 seconds to deliver 1200 cGy to the region where is 1mm away from the balloon surface. The concentric isodose curves were also presented. The Ho-166 is an another alternative for endovascualr irradiation to prevent restenosis after PTCA (Percutaneous Trans Coronary Angioplasty)

• Journal of Chest Surgery
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• v.30 no.4
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• pp.363-372
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• 1997

One hundred forty-four patients underwent operation for coarctation of the aorta at Seoul National University Children's Hospital between June 1986 and Decembsr 1995. Age ranged 0.1 to 191 months. Of these 78.5%(113) were infants. We classified the patients in terms of the anatomic location of coarctatiln and the associatCd anomalies(I[401= primary coarctation, 11(741=isthmic hypoplasia, lIIf30)=tubular hypoplasia involving transverse arch, Ar63 =with ventricular septal defect, B(28)=with other major cardiac defects). Subcalvian flap coarctoplasty(60), resection & anastomosis(44), extended aortoplasty(26), and onlay patch(14) were used as surgical methods. Overall operative mortality was 16.0(23/144)%. The hospital mortality was signific'antly higher in patheints with type 111, subtype B, younger age(under 3 months), extended aortoplasty(p(0.01). However, one-stage total repair in patients with subtype A or B were not found to be a predictor of hospital death. Restenosis had occured in 18 patients among 121 survivals(14. 9%). The mean follow-up period was 29.1 $\pm$28.8(0~129.2) months. Preoperative, immediate postoperative(within 3 months after operation) and postoperative(later than 6 months after operation) echocardiographic data on the dimensions of ascending aorta(AA), transverse arch(TA), an4 aortic isthmus(Al) were available in 77 patients(I=20, ll=42, 111= 15). Preoperative and postoperative aortic isthmus(All) and tra sverse arch indices(TAI), defined as TAIAA & AIIAA respectively, were compared. Immediate postoperative All in type 1, II and TAI in type 111 were significantly smaller in stenotic than non-stenotic group suggesting incomplete relieves of stenotic segment Younger age, subclavian coarctoplasty in patient under 3 months of age were round to be the risk factors for restenosis in this series. In conclusion, We found that aortic arch index and transverse arch index can be a useful tool to figure out the anatomic and clinical characteristics of the patients with aortic coarctation, and that anatomy, associated anomalies, age, and surgical methods may influence the surgical outcome of the coarctation repair.

• Journal of Chest Surgery
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• v.36 no.12
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• pp.929-936
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• 2003

We analysed the surgical outcomes of immediate reoperations after mitral valve repair. Material and Method: Eighteen patients who underwent immediate reoperation for failed mitral valve repair from April 1995 through July 2001 were reviewed retrospectively. There were 13 female patients. The mitral valve disease was regurgitation (MR) in 12 patients, stenosis (MS) in 3, and mixed lesion in 3. The etiologies of the valve disease were rheumatic in 9 patients, degenerative in 8, and endocarditis in 1. The causes of reoperation was residual MR in 13 patients, residual MS in 4, and rupture of left ventricle in 1. Fourteen patients had rerepair for residual mitral lesions (77.8%) and four underwent replacement. Result: There was no early death. After mean follow-vp of 33 months, there was one late death. Echocardiography revealed no or grade 1 of MR (64.3%) in 9 patients and no or mild MS in 11 patients (78,6%). Reoperation was done in one patient. The cumulative survival and freedom from valve-related reoperation at 6 years were 94% and 90%, respectively. The cumulative freedom from recurrent MR and MS at 4 years were 56% and 44%, respectively. Conclusion: This study suggests that immediate reoperation for failed mitral valve repair offers good early and intermediate survival, and mitral valve rerepair can be successfully performed in most of patients. However, because mitral rerepair have high failure rate, especially in rheumatic valve disease, adequate selections of valvuloplasty technique and indication are important to reduce the failure rate of mitral rerepair.

• Journal of Chest Surgery
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• v.38 no.4 s.249
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• pp.291-300
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• 2005

One-stage repair of aortic arch anomalies and intracardiac defects through median sternotomy has been recently adopted by many institutions since it is known to be safer than the staged repair. The early and midterm results of the one-stage repair of aortic arch anomalies and intracardiac defects were retrospectively evaluated. Material and Method: 45 patients who underwent one-stage repair of aortic arch anomalies and intracardiac defects performed by one surgeon from January 1996 to July 2003 were included in this retrospective study. The median age of repair was 16 days (range, 3 days$\~$23.7 months) and the mean weight was $3.62\;\pm\;1.30 kg$. Thirty one $(68.9\%)$ had coarctation and 14 $(31.1\%)$ had interrupted aortic arch. Associated intracardiac anomalies were VSD in 31 patients (VSD group), TGA or Taussig-Bing anomaly in 10 (TGA group), and others in 4 (ASD in 1, aortopulmonary window 1, truncus arteriosus 1, aortic and mitral stenoses 1, miscellaneous group). The arch obstruction was repaired with end-to-side anastomosis in 23 patients and end-to-end anastomosis in 22. Result: Overall postoperative hospital mortality was $22.2\%\;(10/45);\;16.1\%$ (5/31) in VSD group, $40\%$ (4/10) in TGA group, and$25\%$ (1/4) in miscellaneous group. There was no mortality in VSD group since 1998, and the mortality in TGA group has remarkably reduced since technical modification for coronary transfer was adopted $(75\%\;vs\;16.7\%)$. There was no postoperative seizure or other neurological complications. Postoperative aortic restenosis occurred in 5 patients $(5/35,\;14.3\%)$. Two patients underwent balloon aortoplasty with successful results. There was no reoperation. There was one late death caused by pneumonia 5 months after the operation. Two-year actuarial survival rate including operative death was $72.9\%$. Conclusion: The operative mortality of one-stage repair has been reduced with time and aortic restenosis rate was also acceptable. We concluded that this procedure is a reproducible procedure for aortic arch anomalies associated with intracardiac defects.

• Journal of Chest Surgery
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• v.20 no.4
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• pp.859-864
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• 1987

The microwave tissue coagulator was originally used for hemostasis in the hepatic surgery, which is effectively applied in the endoscopic surgery such as the hemostasis of gastric ulcer or tumor bleeding, stenosis relieving of esophageal or rectal stenosis and tumor reduction in inoperable early cancer cases. We experienced the good result of the microwave tissue coagulation therapy in the patient with the restenosis of esophagogastrostomy. The patient was 67 year-old female, who was admitted due to the lye stricture of esophagus for 40 years. We made the lower esophagectomy and the esophagogastrostomy with the upper intact esophagus in the right thorax. But the restenosis occurred at the esophagogastrostomy site because of the polypoid mucosal protrusion at one month after operation. We applied the microwave tissue coagulator 3 times with 6 day interval under esophagoscopy and the good symptomatic and endoscopic relief was alleviated. We think that the microwave tissue coagulation is a very convenient and advisable method in the case of restenosis after esophageal surgery.