• Imaging Science in Dentistry
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• v.40 no.4
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• pp.171-178
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• 2010

Purpose : The purpose of this study is to develop a surgical stent for dental implant procedure that can be easily applied and affordable by using cone beam computerized tomography (CBCT). Materials and Methods : Aluminum, Teflon-PFA (perfluoroalkoxy), and acetal (polyoxymethylene plastic) were selected as materials for the surgical stent. Among these three materials, the appropriate material was chosen using the CBCT images. The surgical stent, which could be easily placed into an oral cavity, was designed with chosen material. CBCT images of the new surgical stent on mandible were obtained using Alphard-3030 dental CT system (Asahi Roentgen Co., Ltd., Kyoto, Japan). The point of insertion was prescribed on the surgical stent with the multiplanar reconstruction software of OnDemand3D (CyberMed Inc., Seoul, Korea). Guide holes were made at the point of insertion on the surgical stent using newly designed guide jig. CBCT scans was taken for the second time to verify the accuracy of the newly designed surgical stent. Results : Teflon-PFA showed radiologically excellent image characteristics for the surgical stent. High accuracy and reproducibility of implantation were confirmed with the surgical stent. Conclusion : The newly designed surgical stent can lead to the accurate implantation and achieve the clinically predictable result.

• Smart Structures and Systems
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• v.8 no.1
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• pp.1-15
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• 2011

Cerebral aneurysm is common lesion among adult population. Current methods for treating the disease have several limitations. Inspired by fern leaves, we have developed a new stent, called leaf stent, which can provide a tailored coverage at the neck of an aneurysm and thus prevent the blood from entering the aneurysm. It alone can be used to treat the cerebral aneurysm and therefore overcomes problems existing in current treating methods. The paper focuses on the numerical simulation of the leaf stents. The mechanical behaviour of the stent in various designs has been investigated using the finite element method. It has been found that certain designs provide adequate radial force and have excellent longitudinal flexibility. The performance of certain leaf stents is comparable and even superior to those of the commercially available cerebral stents such as the Neuroform stent and the Enterprise stent, commonly used for stent assisted coiling, while at the same time, providing sufficient coverage to isolate the aneurysm without using coils.

• Journal of Korean Neurosurgical Society
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• v.48 no.1
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• pp.53-58
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• 2010

Objective : The purpose of this study was to review the safety and durability of aneurysms treated with stent-assisted coiling of ruptured anterior communicating artery aneurysms with small parent vessels (< 2.0 mm). Methods : Retrospective review of all ruptured aneurysm treated with stent assisted endovascular coiling between March 2005 and March 2009 at our institution was conducted. We report 11 cases of the Neuroform stent placement into cerebral vessels measuring less than 2.0 mm in diameter (range, 1.3-1.9 mm) in anterior cerebral artery. Clinical follow-up ranged from 3 to 12 months and imaging follow-up was performed with cerebral angiography at 6 months and 12 months after discharge. Results : Complete occlusion was achieved in 10 patients, and a remnant neck was evident in one. No stent displacement or no dislodgement occurred during stent placement. There was no evidence of thromboembolic complication, arterial dissection and spasm during procedure. We performed follow-up angiography in all patients at 6 months and/or 12 months from the first procedure. The follow-up angiographic data showed successfully results except one in-stent stenosis case. All patients improved clinical performances except one patient with severe vasospasm who showed poor clinical condition initially. Conclusion : We have safely and successfully treated 11 vessels smaller than 2.0 mm in diameter with self-expanding stents with good short and intermediate term results. More clinical data with longer follow-ups are needed to establish the role of stent-assisted coiling in ruptured aneurysms with small parent vessels.

• Journal of Korean Neurosurgical Society
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• v.64 no.1
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• pp.136-141
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• 2021

The crossing Y-stent method is one of the indispensable techniques to achieve sufficient neck coverage during coil embolization of bifurcation aneurysms with a wide neck and/or branch incorporation. However, the inevitable hourglass-like expansion of the second stent at the crossing point can result in insufficient vessel wall apposition, reduced aneurysm neck coverage, delayed endothelialization, and subsequent higher risks of acute or delayed thrombosis. It also interferes with engagement of the microcatheter into the aneurysm after stent installation. We expected to be able to reduce these disadvantages by installing a noncrossing type Y-stent using the Solitaire AB stent, which is fully retrievable with a tapered proximal end. Here we report the techniques and two successful cases.

• Journal of Korean Neurosurgical Society
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• v.53 no.5
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• pp.274-280
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• 2013

Objective : To evaluate the feasibility and clinical and angiographic outcomes of stent-assisted embolization for complex middle cerebral artery (MCA) aneurysms. Methods : The records of 23 consecutive patients with 24 MCA aneurysms, who underwent stent-assisted embolization of the aneurysm, were retrospectively evaluated. Results : Fifteen aneurysms were treated with one stent and 8 were treated using more than two stents (5 a stent-within-a-stent, 1 triple stents, and two Y-stent). Angiographically, complete or near complete occlusion was achieved in 15 aneurysms (65.2%), residual neck in five (21.7%), and residual aneurysm in three (13.1%). Five aneurysms demonstrated thrombosis within the stent during the procedure and hospitalization, and were resolved by intraarterial and intravenous Tirofiban injection. Symptomatic thromboembolic complications were developed in five patients and permanent deficits demonstrated in two patients with modified Rankin Scale 1 and 2, respectively. Treatment-related permanent morbidity and mortality rates were 8.3% and 0% with relatively high complication rate. Angiographic follow-up was available in 17 aneurysms at 6-31 months (mean, 13.2 months) and showed stable or improved in 15 (88.2%) and major and minor recurrence in one, respectively. Conclusion : Complex MCA aneurysms could be treated by stent-assisted coiling and showed lower recanalization rate during mid-term follow-up by effective flow diversion due to various stent-assisted techniques. Our results warrant further study with a longer follow-up period in a larger sample.

• Journal of Yeungnam Medical Science
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• v.33 no.2
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• pp.138-141
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• 2016

Coronary stent dislodgement during percutaneous coronary intervention, which occurs when the stent is passed through tortuous and calcified lesions, is not a rare complication. Without proper treatment, such as fixing with another stent in the coronary artery or removing the undeployed stent from the coronary artery or systemic artery system, this complication can cause serious problems. We experienced the unusual situation of a dismounted and dislodged coronary stent, in which retrograde retrieval to the radial artery was impossible during transradial coronary intervention. We report on use of a rendezvous and snare technique at the brachial artery level via femoral puncture, which resulted in resolution without surgery.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.331-334
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• 2004

In clinical use, coronary stents keep coronary arteries open after expansion with a balloon catheter and prevent the expanded artery from collapsing. Coronary stents are positioned in artery by catheter with a balloon along a guide wire to the lesion site. Flexibility is one of important ability for delivery. In this paper, Palmaz-Schatz stent and Tenax complete stent were selected because these are the most representative of tubular stents. Finite element analyses for the stent system were performed using ABAQUS/Standard code. The present study estimated the flexibility of coronary stents due to loading directions. Moreover the present paper suggests a numerical method to test the flexibility of stents. In conclusion this paper shows how the finite element analysis can be effectively organized in the stent development.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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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.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.518-522
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• 2008

Recently, many patients related to heart disease have surgical operation by expanding a blood vessel to treat the angiostenosis. So far most angioplasties have been performed using balloon-dilative stent made of stainless steel. Some researchers are studying the stent made of shape memory alloy (SMA) to operate the angioplasty more easily. and there are several papers which introduce the angioplasty using SMA. However, most of the analysis models for stents are constructed using solid elements. So much computing time is required to solve the analysis model. In this study, we suggest the SMA stent model using 1D truss element which is much faster than stent model using 3D solid element. To represent non-linear behavior of SMA, we apply 1D SMA constitutive equation of Lagoudas'. Pseudo-elastic behavior of stent structures is presented as a numerical example.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.601-607
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• 2012

In this study, we performed computational fluid dynamic simulations to explore how the detailed design of drug-eluting stents affects both the flow field in the vicinity of the stent as well as the concentration of the eluted drug at the endothelial cell surface. Simulations were performed on three idealized stent geometries we developed and on geometries approximating three commercial stents,: Medtronic's Aurora stent, Cordis's BX Velocity stent, and Boston Scientific's Wallstent. An important contribution of the present study is the introduction of the stent effectiveness index (EI), which provides a quantitative assessment of stent performance and an objective basis for comparing the performance of different stents. Among the three commercial stents studied, our simulations have revealed that the BX Velocity stent is associated with the lowest in-stent EI values for the range of flow Reynolds numbers studied ($200{\leq}Re{\leq}800$). In addition to commercial stent designs, we investigated the EI in three idealized stents and determined that a spiral stent provides excellent performance (low EI) under all flow conditions investigated.