• Proceedings of the KSME Conference
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• 2003.04a
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.7
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• pp.915-922
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• 2004

A stent is small tube-like structure expanded into stenotic arteries to restore blood flow. The stent expansion behaviors define the effectiveness of the surgical operation. In this paper, finite-element method was employed to analyze expansion behaviors and fatigue life of a typical diamond-shaped 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 simulated using commercial FEM code, ANSYS and fatigue life were estimated using NISAII ENDURE. The FEM results showed that the pressures necessary to expand the stent up to a diameter of 3mm, 4mm and 5mm were 0.75MPa, 0.82MPa and 0.97MPa. The fatigue lifes according to expansion diameter were 114${\times}$10$^{7}$cycles, 714${\times}$$^{6}$cycles and 163${\times}$10$^{6}$cycles. As a result, a finite element model used in this study can simulate expansion behaviors of stents and should be useful to design new stents or analyze actual stents.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.156-162
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• 2005

Stouts are frequently used throughout the human body, but the most critical areas are in coronary arteries. They open pathways in vessels and supply blood directly to the heart muscle. To simulate behavior of expansion for the coronary stent by balloon, the commercial finite element code LS-DYNA and ANSYS were used in the analysis. The explicit method is used to analyze the expansion of the stent and the implicit method is performed to simulate the springback that developed in a stent after the balloon pressure has been removed. Finally the experimental results for the expansion of the PS153 stents were compared with the FEM results. The springback was measured with the stents subjected to no external pressure to which stents are subjected in vivo. The simulated results were in good agreement with experimental results. Standard mechanical characteristics such as stress, plastic strains, and springback can be derived from the numerical results. These data can be used to determine maximum expansion diameter without fracture and expansion pressure considering elastic recoil.

• Journal of Korean Neurosurgical Society
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• v.46 no.6
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• pp.572-576
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• 2009

Detachable balloon-based endovascular fistula occlusion is a widely accepted treatment for traumatic carotid cavernous fistulas (CCF). However, more recently coils have been used to obliterate the lesion, especially in case detachable balloon is not available. We failed balloon-assisted coil embolization for CCF because of large fistulas and herniation of coil loops into the parent artery. The authors describe our experiences of balloon-expandable graft-stents to treat CCF, and place emphasis on arterial wall reconstruction. Three traumatic CCF patients were treated using a graft-stent with/without coils, and underwent angiographic follow-up to evaluate the patency of the internal carotid artery (ICA). In all cases, symptoms related to CCF regressed after stent deployment and did not recur during follow-up. Follow-up angiography revealed good patency of the ICA in all patients. Graft-stents should be considered as an alternative means of treating CCF and preserving the parent artery by arterial wall reconstruction especially in patients with a fistula that cannot be successfully occluded with detachable balloons or coils.

• Journal of Korean Neurosurgical Society
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• v.50 no.1
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• pp.48-50
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• 2011

A 57-year-old man presented with a 2-day history of left oculomotor palsy. Digital subtraction angiography revealed a pseudoaneurysm of the left cavernous internal carotid artery (ICA) measuring $37{\times}32mm$. The pseudoaneurysm was treated with a balloon expandable graft-stent to occlude the aneurysmal neck and preserve the parent artery. A post-procedure angiogram confirmed normal patency of the ICA and complete sealing of the aneurysmal neck with no opacification of the sac. After the procedure, the oculomotor palsy improved gradually, and had completely resolved 3 months after the procedure. A graft-stent can be an effective treatment for a pseudoaneurysm of the cavernous ICA with preservation of the parent artery.

• Tuberculosis and Respiratory Diseases
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• v.39 no.4
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• pp.318-324
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• 1992

Acquired tracheobronchial stenosis has resulted from vehicular accidents, prolonged tracheal intubation, sleeve resection, tuberculosis and sarcodosis. Various modalities of therapy for the relief of such stenosis included surgery, cryotherapy, laser photoresection, and sometimes balloon dilatation. Several recent reports have described the use of self-expandable metal stents for the dilatation of stenotic areas in the tracheobronchial tree. Three patients of benign acquired tracheobronchial stenosis were treated with self-expandable metal stents, who had shown little response to several times of balloon dilatations; One patient had a tracheal stenosis caused by intubation, one a right main bronchial stenosis developed after reconstructive surgery of traumatic bronchial rupture, and the other a left main bronchial stenosis caused by longstanding endobronchial tuberculosis. We found that the using stent in benign acquired tracheobronchial stenosis can be effectively performed with alleviation of clinical symptoms and lung function. And even in longstanding localized stenosis of main bronchus without distal bronchial destruction, lung perfusion also improved.

• Journal of Chest Surgery
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• v.33 no.1
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• pp.107-111
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• 2000

Although a tracheal stent can be an option for inoperable tracheal stenoses there still are some troublesome side effects including overgranulation from foreign body irritation restenosis and patient's discomfort associated with the procedure. We report a successful case of a retrievable stent made of self-expandable 'shape memory' metal and polyurethane in a 24 year old female patient with respiratory distress and tight stenosis in the trachea and left main bronchus, The stent was inserted following a balloon dilatation and was successfully removed on the 7th days after the procedure. She regained a normal active life without any repiratory symptoms and a follow-up of 8 months showed satisfactory results.

• Journal of Korean Neurosurgical Society
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• v.45 no.5
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• pp.284-288
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• 2009

Objective : Our retrospective study aimed to determine whether 16-slice computerized tomography (CT) angiography optimized sharp kernel is suitable for the evaluation of visibility, luminal patency and re-stenosis of intracranial stents in comparison with conventional angiography. Methods : Fifteen patients with symptomatic intracranial stenotic lesions underwent balloon expandable stent deployment of these lesions (10 middle cerebral arteries, 2 intracranial vertebral arteries, and 3 intracranial internal carotid arteries). CT angiography follow-up ranged from 6 to 15 months (mean follow-up, 8 months) after implantation of intracranial stents and conventional angiography was confirmed within 2 days. Curved multiplanar reformations with maximal intensity projection (MIP) with optimal window settings for assessment of lumen of intracranial stents were evaluated for visible lumen diameter, stent patency (contrast distal to the stent as an indirect sign), and re-stenosis by two experienced radiologists who blinded to the reports from the conventional angiography. Results : All of stents deployed into symptomatic stenotic lesions. All stents were classified as patent and no re-stenosis, which was correlated with results of conventional angiography. Parts of the stent lumen could be visualized in all cases. On average, 57% of the stent lumen diameter was visible using optimized sharp kernel. Significant improvement of lumen visualization (22%, p<0.01) was observed using the optimized sharp kernel compared with the standard sharp kernel. Inter-observer agreements on the measurement of lumen diameter and density were judged as good, respectively (p<0.05). Conclusion : Sixteen-slice CT using the optimized sharp kernel may provide a useful information for evaluation of lumen diameter patency, and re-stenosis of intracranial stents.

• Journal of Korean Neurosurgical Society
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• v.50 no.4
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• pp.322-326
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• 2011

Objective : Stenting of symptomatic intracranial stenosis has recently become an alternative treatment modality. However, urgent intracranial stenting in patients with intracranial stenosis following a transient ischemic attack (TIA) or minor stroke is open to dispute. We sought to assess the feasibility, safety, and effectiveness of urgent intracranial stenting for severe stenosis (>70%) in TIA or minor stroke patients. Methods : Between June 2009 and October 2010, stent-assisted angioplasty by using a balloon-expandable coronary stent for intracranial severe stenosis (>70%) was performed in 7 patients after TIA and 5 patients after minor stroke (14 stenotic lesions). Technical success rates, complications, angiographic findings, and clinical outcomes were retrospectively analyzed. Results : Stenting was successful in all 12 patients. The mean time from symptom onset to stenting was 2.1 days (1-8 days). Post-procedural angiography showed restoration to a normal luminal diameter in all patients. In-stent thrombosis occurred in one patient (n=1, 8.3%), and was lysed with abciximab. No device-related complications, such as perforations or dissections at the target arteries or intracranial hemorrhaging, occurred in any patient. The mortality rate was 0%. No patient had an ischemic event over the mean follow-up period of 12.5 months (range, 7-21 months), and follow-up angiography (n=7) revealed no significant in-stent restenosis (>50%). Conclusion : Urgent recanalization with stenting is feasible, safe, and effective in patients with TIA or acute minor stroke with intracranial stenosis of ${\geq}$ 70%.

• Journal of Chest Surgery
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• v.39 no.12 s.269
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• pp.927-930
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• 2006

Hybrid procedure was performed for a thirteen-day-old girl with a functionally single ventricle, who weighed 2.2 kg and had been prematurely born at $32^{+5}$ weeks of gestation. She underwent bilateral pulmonary artery banding using 3.5 mm Gore-Tex graft, ductal stenting using balloon expandable stent, and reverse Blalock-Taussig shunt with 3.5 mm Gore-Tex vascular graft. After discharge, she was followed up for 4 months, and underwent 2nd stage operation(extensive arch reconstruction with Damus-Kaye-Stansel anastomosis, atrial septectomy, bilateral pulmonary artery angioplasty, bidirectional cavopulmonary shunt). She has been followed up for 4 months after the 2nd operation with an excellent clinical condition.