• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.485-490
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• 2003

In this paper, a nonlinear finite-element method was employed to analyze mechanical behaviors of the balloon-expandable stent. Beyond safety considerations, this type of analysis provides mechanical properties that are often difficult to obtain by experiments. Mechanical properties of the stent expansion pressure, radial recoil, longitudinal recoil and foreshortening were studied using commercial FEM code, ANSYS. As a result, the pressure necessary to expand the stent up to a diameter of 3mm was 7.6atm, longitudinal recoil, radial recoil and foreshortening were -0.388%, 2.87% and 4.07% respectively. In conclusion, a finite element model used in this study could help in designing new stents or analyzing actual stents.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1306-1309
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• 2003

In the present paper, finite element analyses were carried out to evaluate the most important feature of a stent, that is. high radial strength and flexibility. Palmaz-Schatz 154 stent and two new models(stent A, stent B) were selected because they are the most representatives of tubular stents. Finite element analyses for the stent system were performed using ABAQUS/Explicit code. As a result, Palmaz-Schatz 154 stent shows sufficient radial strength but it needs some improvement in general properties such as high flexibility, low elastic recoil, low longitudinal contraction and low metal coverage area. Other two models show that sufficient flexibility, foreshortening and longitudinal recoil.

• Biomaterials and Biomechanics in Bioengineering
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• 제1권3호
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• pp.131-150
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• 2014

Vascular stenting has a great attention as a treatment for coronary arteries diseases as compared with percutaneous balloon angioplasty. In-stent restenosis and thrombosis are side effects resulting from using bare metal stent (BMS). Employing platelet therapy allowed to reduce the rate of thrombosis, however, the rate of restenosis remains a major problem. In 2002, drug-eluting stents (DESs) were introduced as an effort to reduce the restenosis. The commercially available DESs continue to suffer from coating defects that might lead to a series of adverse effects. Most importantly, multiple concerns remain regarding the polymer coating integrity on metal surfaces or the relation of polymer irregularities to longterm adverse events.

• Nuclear Medicine and Molecular Imaging
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• 제40권2호
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• pp.106-112
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• 2006

Tissue hyperplasia is one of the most frequently encountered complications when self-expanding metallic stents are placed in benign non-vascular luminal organ strictures, thus causing restenosis of the lumen. The investigators postulated that ionizing irradiation could be applied to prevent restenosis caused by tissue hyperplasia in non-vascular luminal organs as it reduced coronary or peripheral arterial narrowing successfully. The authors combined $\beta$-irradiation using $^{188}Re-MAG_3$ solution with balloon dilation for animal and clinical studies because this new treatment approach had the advantages such as low penetration depth of $\beta$-ray, self-centering irradiation, and mechanical effect of balloon dilation over using $\gamma$-irradiation with afterloading devices in this article, the concept and mechanism of radioisotope balloon dilation, and animal and clinical studies using radioisotope balloon dilation are reviewed.

• Journal of Medicine and Life Science
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• 제20권3호
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• pp.131-134
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• 2023

Here, we present a case of a 56-year-old man with acute myocardial infarction. The patient underwent percutaneous coronary intervention (PCI) at the left main bifurcation and mid-left anterior descending artery using drugeluting stents. Four months after the PCI, the patient was readmitted for cardiac arrest. Coronary angiography (CAG) revealed stent thrombosis in the left main-to-proximal left anterior descending artery and in-stent restenosis in the left main-to-proximal left circumflex artery. We performed balloon angioplasty at the left main to mid-left anterior descending artery and left main to proximal left circumflex artery stents; subsequently, blood flow was fully restored. However, contrast agent extravasation was observed outside the mid-portion of the left main artery to the proximal left anterior descending artery stent, indicating the presence of a coronary artery aneurysm (CAA) outside the stent. After guideline-directed medical therapy with dual antiplatelet agents and high-intensity statins, follow-up CAG revealed near-resolution of the CAA, absence of stenotic lesions, and good blood flow.

• Korean Circulation Journal
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• 제48권11호
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• pp.1030-1031
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• 2018

• 폴리머
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• 제34권2호
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• pp.172-177
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• 2010

최근 20년간 다양한 세포에서 파크리탁셀(PTX)의 효과에 관한 연구는 많이 있지만, 세포증식을 억제하기 위한 약물방출 동역학에 관한 연구는 거의 보고되지 않고 있다. 본 연구에서는 약물방출스텐트 (DES)에 적용하기 위해서 생분해성 고분자로부터 파크리탁셀의 방출거동을 고찰하였다. 다양한 생분해성 고분자인 poly(lactic acid-co-glycolic acid) (PLGA), poly-L-lactide(PLLA) 및 polycaprolactone(PCL)에 파크리탁셀의 함유량을 달리하여 필름을 제조한 후 약물방출 거동을 평가하였다. 약물방출은 8주 동안 이루어졌으며 FE-SEM을 통해 고분자의 분해정도를 관찰하였다. PCL의 생분해 속도는 가장 느리지만 파크리탁셀의 함량이 같을 경우 PCL로부터의 파크리탁셀 방출속도가 가장 빨랐으며 PLGA 그리고 PLLA 순서를 보였다. 이와 같은 결과를 바탕으로 PCL과 같이 유리전이온도($T_g$)가 낮은 고분자의 경우 체내에서 파크리탁셀과 같은 소수성 약물의 움직임이 용이하기 때문에 약물방출 속도가 빠를 수 있음을 제시하고 있다.

• 한국CDE학회논문집
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• 제16권3호
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• pp.216-226
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• 2011

Surgeon dentists usually rely on their experiential judgments from patients' oral plaster casts and medical images to determine the positional and directional information of implant fixtures and to perform drilling tasks during dental implant surgical operations. This approach, however, may cause some errors and deteriorate the quality of dental implants. Computer-aided methods have been introduced as supportive tools to alleviate the shortcomings of the conventional approach. In this paper, we present an approach of 3D dental implant simulation which can provide the realistic and immersive experience of dental implant information. The dental implant information is primarily composed of several kinds of 3D mesh models obtained as follows. Firstly, we construct 3D mesh models of jawbones, teeth and nerve curves from the patient's dental images using software $Mimics^{TM}$. Secondly, we construct 3D mesh models of gingival regions from the patient's oral impression using a reverse engineering technique. Thirdly, we select suitable types of implant fixtures from fixture database and determine the positions and directions of the fixtures by using the 3D mesh models and the dental images with software $Simplant^{TM}$. Fourthly, from the geometric and/or directional information of the jawbones, the gingival regions, the teeth and the fixtures, we construct the 3D models of surgical guide stents which are crucial to perform the drilling operations with ease and accuracy. In the application phase, the dental implant information is combined with the tangible interface device to accomplish 3D dental implant simulation. The user can see and touch the 3D models related with dental implant surgery. Furthermore, the user can experience drilling paths to make holes where fixtures are implanted. A preliminary user study shows that the presented approach can be used to provide dental students with good educational contents. With future work, we expect that it can be utilized for clinical studies of dental implant surgery.

• Journal of Korean Neurosurgical Society
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• 제64권6호
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• pp.853-863
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• 2021

Objective : Biodegradable poly-L-lactic acid (PLLA) with a highly biocompatible surface via tantalum (Ta) ion implantation can be an innovative solution for the problems associated with current biodegradable stents. The purpose of this study is to develop a Taimplanted PLLA stent for clinical use and to investigate its biological performance capabilities. Methods : A series of in vitro and in vivo tests were used to assess the biological performance of bare and Ta-implanted PLLA stents. The re-endothelialization ability and thrombogenicity were examined through in vitro endothelial cell and platelet adhesion tests. An in vivo swine model was used to evaluate the effects of Ta ion implantation on subacute restenosis and thrombosis. Angiographic and histologic evaluations were conducted at one, two and three months post-treatment. Results : The Ta-implanted PLLA stent was successfully fabricated, exhibiting a smooth surface morphology and modified layer integration. After Ta ion implantation, the surface properties were more favorable for rapid endothelialization and for less platelet attachment compared to the bare PLLA stent. In an in vivo animal test, follow-up angiography showed no evidence of in-stent stenosis in either group. In a microscopic histologic examination, luminal thrombus formation was significantly suppressed in the Ta-implanted PLLA stent group according to the 2-month follow-up assessment (21.2% vs. 63.9%, p=0.005). Cells positive for CD 68, a marker for the monocyte lineage, were less frequently identified around the Ta-implanted PLLA stent in the 1-month follow-up assessments. Conclusion : The use of a Ta-implanted PLLA stent appears to promote re-endothelialization and anti-thrombogenicity.

• Journal of Korean Neurosurgical Society
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• 제64권5호
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• pp.818-826
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• 2021

Objective : The widely accepted treatment option of a traumatic carotid cavernous fistula (TCCF) has been detachable balloon or coils based fistula occlusion. Recently, covered stent implantation has been proving an excellent results. The purpose of this study is to investigate our experiences with first line choice of covered stent implantation for TCCF at level 1 regional trauma center. Methods : From November 2004 to February 2020, 19 covered stents were used for treatment of 19 TCCF patients. Among them, 15 cases were first line treatment using covered stents. Clinical and angiographic data were retrospectively reviewed. Results : Procedures were technically successful in all 15 cases (100%). Immediate angiographic results after procedure were total occlusion in 12 patients (80%). All patients except two expired patients had image follow-up (mean 15 months). Recurred symptomatic three patients underwent additional treatments and achieved complete occlusion. Mean clinical follow-up duration was 32 months and results were modified Rankin Scale 1-2 in five, 3-4 in five, and 5 in three patients. Conclusion : The covered stent could be considered as fist line treatment option for treating TCCF patients especially in unstable vital sign. Larger samples and expanded follow-up are required to further develop their specifications and indications.