• Clinical Endoscopy
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• v.57 no.5
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• pp.595-603
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• 2024

Background/Aims: Coaxial placement of double pigtail plastic stents (DPPS) through lumen-apposing metal stents (LAMSs) is commonly performed to reduce the risk of LAMS obstruction, bleeding, and stent migration when used for the drainage of pancreatic fluid collections (PFCs). A systematic review and meta-analysis were performed to compare the outcomes of LAMS alone and LAMS with coaxial DPPS placement in the management of PFCs. Methods: A systematic review was conducted to identify studies comparing LAMS and LAMS/DPPS for PFC drainage. Primary outcomes included the rate of clinical success, overall adverse events (AEs), bleeding, infection, occlusion, and stent migration. The pooled effect size was summarized using a random-effects model and compared between LAMS and LAMS/DPPS by calculating odds ratios (ORs). Results: Nine studies involving 709 patients were identified (338 on LAMS and 371 on LAMS/DPPS). LAMS/DPPS was associated with a reduced risk of stent obstruction (OR, 0.59; p=0.004) and infection (OR, 0.55; p=0.001). No significant differences were observed in clinical success (OR, 0.96; p=0.440), overall AEs (OR, 0.57; p=0.060), bleeding (OR, 0.61; p=0.120), or stent migration (OR, 1.03; p=0.480). Conclusions: Coaxial DPPS for LAMS drainage of PFCs is associated with a reduced risk of stent occlusion and infection; however, no difference was observed in the overall AE rates or bleeding.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.1-6
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• 2017

Stents are widely used as the most common method of treating coronary artery disease with implants in the form of a metal mesh. The blood flow is normalized by inserting a stent into the narrowed or clogged areas of the human body. In this study, the mechanical characteristics of a stent are investigated according to the variations of its design parameters by the Taguchi method and finite element analysis. A stent model of the Palmaz-Schatz type was used for the analysis. In the analysis, an elasto-plastic material model was adopted for the stent and a hyper-elastic model was used for the balloon. The main interest of this study is to investigate the effects of the design parameters which reduce the possibility of restenosis by adjusting the recoil amount. A Taguchi orthogonal array was constructed on the model of the stent. The thickness and length and angle of the slot were selected as the design parameters. The amounts of radial recoil and longitudinal recoil were calculated by finite element analysis. The statistical analysis using the Taguchi method showed that optimizing the shape of the stent could reduce the possibility of restenosis. The optimized shape showed improvements of recoil in the radial and longitudinal directions of ~1% and ~0.1%, respectively, compared to the default model.

• Journal of Korean Neurosurgical Society
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• v.57 no.5
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• pp.342-349
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• 2015

Background : Higher reperfusion rates have been established with endovascular treatment for acute ischemic stroke patients. There are limited data on the comparative performance of mechanical thrombectomy devices. This study aimed to analyse the efficacy and safety of the stent retriever device (Solitaire stent) by comparing procedure time, angiographic outcome, complication rate and long term clinical outcome with previous chemical thrombolysis and mechanical thrombectomy using penumbra system. Method : A retrospective single-center analysis was undertaken of all consecutive patients who underwent chemical thrombolysis and mechanical thrombectomy using Penumbra or Solitaire stent retriever from March 2009 to March 2014. Baseline characteristics, rate of successful recanalization (modified Thrombolysis in Cerebral Infarction score 2b-3), symptomatic intracerebral hemorrhage, procedure time, mortality and independent functional outcomes ($mRS{\leq}2$) at 3 month were compared across the three method. Results : Our cohort included 164 patients, mechanical thrombectomy using stent retriever device had a significant impact on recanalization rate and functional independence at 3 months. In unadjusted analysis mechanical thrombectomy using Solitaire stent retriever showed higher recanalization rate than Penumbra system and chemical thrombolysis (75% vs. 64.2% vs. 49.4%, p=0.03) and higher rate of functional independence at 3 month (53.1% vs. 37.7% vs. 35.4%, p=0.213). In view of the interrelationships between all predictors of variables associated with a good clinical outcome, when the chemical thrombolysis was used as a reference, in multiple logistic regression analysis, the use of Solitaire stent retriever showed higher odds of independent functional outcome [odds ratio (OR) 2.62, 95% confidence interval (CI) 0.96-7.17; p=0.061] in comparison with penumbra system (OR 1.57, 95% CI 0.63-3.90; p=0.331). Conclusion : Our initial data suggest that mechanical thrombectomy using stent retriever is superior to the mechanical thrombectomy using penumbra system and conventional chemical thrombolysis in achieving higher rates of reperfusion and better outcomes. Randomized clinical trials are needed to establish the actual benefit to specific patient populations.

• Progress in Medical Physics
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• v.20 no.3
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• pp.119-124
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• 2009

Stents are frequently used throughout the human body. They keep pathways open in vascular or nonvascular duct for a long time. Therefore its stability is very important factor. In recent years, aconsiderable amount of research has been carried out in order to estimate mechanical properties of the stent such as expansion pressure behavior, radial recoil and longitudinal recoil using FEM (Finite element analyses). However, published works on simulation of stent fatigue behavior using FEM are relatively rare. In this paper, a nonlinear finite-element methodwas employed to analyses the compression of a stent using external pressure and fatigue behavior. Finite element analyses for the stent system were performed using NASTRAN FX. In conclusion this paper shows how the stent is behaved in the body, and its fatigue behavior.

• Imaging Science in Dentistry
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• v.42 no.3
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• pp.139-146
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• 2012

Purpose: An individual surgical stent fabricated from computed tomography (CT) data, called a CT-guided stent, would be useful for accurate installation of implants. The purpose of the present study was to introduce a newly developed CT-guided stent with a simple design and evaluate the accuracy of the stent placement. Materials and Methods: A resin template was fabricated from a hog mandible and a specially designed plastic plate, with 4 metal balls inserted in it for radiographic recognition, was attached to the occlusal surface of the template. With the surgical stent applied, CT images were taken, and virtual implants were placed using software. The spatial positions of the virtually positioned implants were acquired and implant guiding holes were drilled into the surgical stent using a specially designed 5-axis drilling machine. The surgical stent was placed on the mandible and CT images were taken again. The discrepancy between the central axis of the drilled holes on the second CT images and the virtually installed implants on the first CT images was evaluated. Results: The deviation of the entry point and angulation of the central axis in the reference plane were $0.47{\pm}0.27$ mm, $0.57{\pm}0.23$ mm, and $0.64{\pm}0.16^{\circ}$, $0.57{\pm}0.15^{\circ}$, respectively. However, for the two different angulations in each group, the $20^{\circ}$ angulation showed a greater error in the deviation of the entry point than did the $10^{\circ}$ angulation. Conclusion: The CT-guided template proposed in this study was highly accurate. It could replace existing implant guide systems to reduce costs and effort.

• Proceedings of the KAIS Fall Conference
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• 2000.10a
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• pp.30-33
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• 2000

최근 국내에서도 관 동맥 질환 환자의 수가 급증하고 있으며, 관 동맥 질환의 치료 방법인 관 동맥 성형 술은 관 동맥 stent의 도입에 의하여 보편화되어 국내에서 년간 5000개 이상의 stent가 시술되고 있다. 그러나 stent는 고가(1,200천원/개)로 전량 수입에 의존하고 있으며, 시술 후 사망까지 이를 수 있는 혈전에 의한 급성 페쇠와 재 협착이 문제점이다. 이를 위한 한가지 방법이 생체 적합성이 뛰어난 복합 stent의 개발인데 SiC나 Carbon을 coating한 stent는 시술 후 혈전 형성을 억제하는 것으로 알려져 있다. 특히 가장 순수한 Pyrolytic carbon은 hemocompatibility가 탁월하고 기밀 성이기 때문에 본 연구에서 그의 CVB-Kinetics를 연구코저 하는 것이다. methane으로부터 pyrolytic carbon의 CVD는 온도에 따라서 다양한 구조를 가지며 따라서 그의 mechanism도 다양하다는 것은 잘 알려져 있다. 더구나 광간(균질)반응과 표면(불균질)반응의 정량적 관계에 따라서도 다르다는 것도 확인되었다. 그러나 stainless steel 316L로 만든 stent는 12 - 15 %의 Ni과 2%의 Mo을 함유해서 금속성을 잃지 않는 저온(600℃)에서도 pyrolytic carbon의 속매적 CVD가 가능함을 그리고 SiC의 코팅에 적합한 buffer layer 역할을 함을 확인하였다. 그리하여 본 연구는 반응기 설계에 필요한 저온 촉매적 pyrolytic carbon의 CVD-kinetics의 연구결로 그의 mechanism과 함께 rate law 식을 유도, 확인하였으며 600℃, 90kPa에서 P/sub ch4//P/sub H2/=5:1과 체류시간 1.8 sec가 최적임을 발견하였다. 이때 석출속도 11.2 g-mol/g-cat.h 혹은 두께속도로 73 nm/sec를 나타내었다.메타놀-물 (1 : 1) 유출액에서 $(0.80\;{\mu}g)$ 검출되었다. 하면 morey eel내장에서 얻은 독물질도 DEAE-셀루로즈에서 ST-1 과 ST-2로 나누어지며, 이 ST-1의 TLC, HPLC 및 알루미나 컬럼상의 거동이 파랑비늘돔에서 얻은 ST-1의 그것과 같으므로 scaritoxin으로 보고한 ST-1은 ciguatoxin의 형태인 less polar cigutoxin (LPCTX) 으로 생각된다.에서 각각 대조구의 57, 413 및 315% 증진되었다. 거품의 열안정성은 15분 whipping시, pH 4.0(대조구, 30.2%) 및 5.0(대조구, 23.7%)에서 각각 $0{\sim}38.0$ 및 $0{\sim}57.0%$이었고 pH 7.0(대조구, 39.6%) 및 8.0(대조구, 43.6%)에서 각각 $0{\sim}59.4$ 및 $36.6{\sim}58.4%$이었으며 sodium alginate 첨가시가 가장 양호하였다. 전체적으로 보아 거품안정성이 높은 것은 열안정성도 높은 경향이며, 표면장력이 낮으면 거품형성능이 높아지고, 비점도가 높으면 거품안정성 및 열안정성이 높아지는 경향이 있었다.protocol.eractions between application agents that are developed using different languages. Dynamic agent invocation is accomplished by Java Native Interface(JNI) that links two heterogeneous methods, and by KQML language interface that facilitates the communications between heterogeneous agents. This scheme of dyna

• Journal of the Korean Society of Radiology
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• v.6 no.2
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• pp.93-98
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• 2012

Micro-computed tomography (microCT) is an important tool for preclinical vascular imaging, with micron-level resolution. This non-destructive means of imaging allows for rapid collection of 2D and 3D reconstructions to visualize specimens prior to destructive analysis such as pathological analysis. Objectives. The aim of this study was to suggest a method for ex vivo, postmortem examination of stented arterial segments with microCT. And ex vivo evaluation of stents such as bare metal or drug eluting stents on in-stent restenosis (ISR) in rabbit model was performed. The bare metal stent (BMS) and drug eluting stent (DES, paclitaxel) were implanted in the left or right iliac arteries alternatively in eight New Zealand white rabbits. After 4 weeks of post-implantation, the part of iliac arteries surrounding the stent were removed carefully and processed for microCT. Prior to microCT analysis, a contrast medium was loaded to lumen of stents. All samples were subjected to an X-ray source operating at 50 kV and 200 ${\mu}A$ by using a 3D isotropic resolution. The region of interest was traced and measured by CTAN analytical software. Objects being exposed to radiation had different Hounsfield unit each other with values of approximately 1.2 at stent area, 0.12 ~ 0.17 at a contrast medium and 0 ~ 0.06 at outer area of stent. Based on above, further analyses were performed. As a result, the difference of lengths and volumes between expanded stents, which may relate to injury score in pathological analysis, was not different significantly. Moreover, ISR area of BMS was 1.6 times higher than that of DES, indicating that paclitaxel has inhibitory effect on cell proliferation and prevent infiltration of restenosis into lumen of stent. And ISR area of BMS was higher ($1.52{\pm}0.48mm^2$) than that of DES ($0.94{\pm}0.42mm^2$), indicating that paclitaxel has inhibitory effect on cell proliferation and prevent infiltration of restenosis into lumen of stent. Though it was not statistically significant, it showed that the extent of neointema of mid-region of stents was relatively higher than that of anterior and posterior region in parts of BMS as showing cross-sectional 2-D image. suggest that microCT can be utilized as an accessorial tool for pathological analysis.

• Clinical and Experimental Pediatrics
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• v.46 no.1
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• pp.67-75
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• 2003

Purpose : Intravascular stent implantation for the treatment of postoperative branch pulmonary artery(PA) stenosis has been used successfully. However, the cross sectional area of contralateral branch PA does not regress in spite of the successful dilation of the stenotic branch PA after stent implantation. We analyzed the morphologic and hemodynamic factors on the size of branch PA after successful stent implantation. Methods : The subjects in our study were 23 children who had undergone stent implantaion from Jan. 1995 to Jul. 2002 in the Division of Yonsei Pediatric Cardiology. We evaluated the cross sectional area index(CSAI) of branch PA before and after stent implantation at follow-up catheterization. We also investigated factors such as residual pulmonary stenosis, pulmonary regurgitation(PR), systolic pressure of right ventricle, and lung perfusion scan. Results : The CSAI of the RPA without stenosis changed from mean $238{\pm}17mm^2/BSA$ to mean $249{\pm}20mm^2/BSA$(P=0.47), but didn't regress. The CSAI of the LPA with stenosis was increased effectively by stent implantation from the mean $102{\pm}12mm^2/BSA$ to mean $125{\pm}11mm^2/BSA$(P< 0.05). At follow up after stent implantation, the CSAI of PA is correlated with the residual PR fraction after stent implantation. Conclusion : In a group with increased residual PR, CSAI of RPA was found to be significantly increased between the pre- and post-stages of stent implantation. So, we suspect that the pulmonary regurgitation remaining after right ventricle outlet tract(RVOT) dilatation surgery is correlated with the increase in CSAI of RPA.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1493-1494
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1495-1496
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• 2011