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During a maximum follow-up of 18 months, there was no stent migration or esophageal perforation. Most complications could be treated by the interventional radiologist. Conclusion: Self-expandable, covered Nitinol stents provide an option for the treatment of dysphagia combined with esophageal fistulae. In combination with interventional radiology techniques, even complex strictures are accessible. For benign strictures, the value of stent treatment has not yet been proven.

Results of the new nitinol self-expandable stents for distal biliary structures. The nitinol stent is a self-expandable spiral stent made of nickel-titanium alloy. We performed a pilot study to evaluate the method of stent insertion and stent efficacy. Twenty-eight patients with irresectable malignancy had nitinol stents inserted for obstructive jaundice due to distal biliary.

Self-expandable nitinol stent placement in homocysteinemic porcine aorta. Full Text Available PURPOSE: To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs induced with a methionine-rich diet following placement of a self-expanding nitinol stent. They were older than eight weeks in age and had an average weight of 30 kg.

Pigs were randomly divided into two groups. The first, Group C control, was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia. The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography. Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis.

When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M. There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group.

Monitorizing nitinol alloy surface reactions for biofouling studies. Dinu, C. Growth and deposition of unwanted bacteria on implant metal alloys affect their use as biomedical samples. Monitoring any bacterial biofilm accumulation will provide early countermeasures. For a reliable antifouling strategy we prepared nitinol NiTi thin films on Ti-derived substrates by using a pulsed laser deposition PLD method.

As the microstructure of Ti-alloy is dictated by the tensile strength, fatigue and the fracture toughness we tested the use of hydrogen as an alloying element. X-ray diffraction XRD , scanning electron microscopy SEM and atomic force microscopy AFM investigated the crystalline structure, chemical composition and respectively the surface morphology of the nitinol hydrogen and hydrogen-free samples. Moreover, the alloys were integrated and tested using a cellular metric and their responses were systematic evaluated and quantified.

Our attractive approach is meant to select the suitable components for an effective and trustworthy anti-fouling strategy. A greater understanding of such processes should lead to novel and effective control methods that would improve in the future implant stability and capabilities. Fatigue of Nitinol : The state-of-the-art and ongoing challenges.

Nitinol , a nearly equiatomic alloy of nickel and titanium, has been considered for a wide range of applications including medical and dental devices and implants as well as aerospace and automotive components and structures. The realistic loading condition in many of these applications is cyclic; therefore, fatigue is often the main failure mode for such components and structures. The fatigue behavior of Nitinol involves many more complexities compared with traditional metal alloys arising from its uniqueness in material properties such as superelasticity and shape memory effects.

In this paper, a review of the present state-of-the-art on the fatigue behavior of superelastic Nitinol is presented. Various aspects of fatigue of Nitinol are discussed and microstructural effects are explained. Effects of material preparation and testing conditions are also reviewed.

Finally, several conclusions are made and recommendations for future works are offered. All rights reserved. The surface of Nitinol alloy was activated by a thermo-chemical treatment and hydroxyapatite coating was electrodeposited on the alloy, followed by applying the polymer coating. The data revealed that the hydroxyapatite coating is composed of one-dimensional nano sized fl A torsional artificial muscle from twisted nitinol microwire. A work density of up to MPa can be achieved from these microwires.

In the present work, we are showing that by twisting the microwires in form of closed-loop two-ply yarn we can create a torsional actuator. We measured a gravimetric torque of up to These remarkable performance results are comparable to those of guest-infiltrated carbon nanotube twisted yarns. A previous paper Duerig and Bhattacharya in Shap Mem Superelasticity , introduced several engineering considerations surrounding the R-phase in Nitinol and highlighted a common, if not pervasive, misconception regarding the use of the term Af by the medical device industry.

This paper brings additional data to bear on the issue and proposes more accurate terminology. Moreover, a variety of tools are used to establish the forward and reverse stress-temperature phase diagrams for a superelastic wire typical of that used in medical devices. Once established, the two most common methods of measuring transformation temperatures, Differential Scanning Calorimetry and Bend Free Recovery, are tested against the observed behavior.

The use of silicone- or metal stents in stenosis of the distal trachea and the bronchial system is a customary procedure [], for example after tumor invasion or cicatricial stenosis after transplantation. In the proximal part of the trachea, on smaller, short and soft strictures we try to stabilise the trachea by the implantation of rings.

Other methods are tracheal plasty or transverse tracheal resectomy []. In the case of longer or nearer subglottal stenoses the positioning of self-expanding nitinol stents has proven a simple, gentle and well-tolerated alternative procedure even in very serious disorders [1, 8, 9]. These stents can be placed in short narcosis under endoscopic control without great strain on the patient. We placed nitinol -stents in the proximal part of the trachea in eleven cases. In five cases dyspnoea caused by a tracheal collapse improved.

In two further cases a tracheal stenosis with massive granulation tissue and cicatricial pull under an inlaid tracheal cannula was removed and the tracheostoma was closed. In four cases a solid, scarred and cartilaginous stenosis in the area of the cricoid and the upper tracheal rings was widened with laser and later on stented. Over an observation time of two years no complications showed safe one case in which a directly postoperative dislocation was repositioned quickly.

The patients live without restrictions through the tracheal stenosis or a tracheostoma. In the best possible case epithelialization over the metal meshes develops so that a nearly normal mucus transportation is possible [1, ]. The widespread acceptance of carotid artery stenting CAS to treat carotid artery stenosis and its effectiveness compared with surgical counterpart, carotid endarterectomy CEA , is still a matter of debate.

Transient or permanent neurological deficits may develop in patients undergoing CAS due to distal embolization or hemodynamic changes. Design, development, and usage of embolic protection devices EPDs , such as embolic protection filters, appear to have a significant impact on the success of CAS. Unfortunately, some drawbacks, such as filtering failure, inability to cross tortuous high-grade stenoses, malpositioning and vessel injury, still remain and require design improvement.

Currently, many different designs of such devices are available on the rapidly growing dedicated market. In spite of such a growing commercial interest, there is a significant need for design tools as well as for careful engineering investigations and design analyses of such nitinol devices.

The present study aims to investigate the embolic protection filter design by finite element analysis. Subsequently, we used the finite element method to simulate the deployment of the nitinol filter as it exits the delivery sheath. Comparison of the simulations with micro-CT images of the real device exiting the catheter showed excellent correspondence with our simulations. Finally, we evaluated circumferential basket-vessel wall apposition of a 4 mm size filter in a straight vessel of different sizes and shape.

We conclude that the proposed methodology offers a useful tool to evaluate and to compare current or new designs of EPDs. Further simulations will investigate vessel wall apposition in a realistic tortuous anatomy. Feasibility study for the investigation of Nitinol self-expanding stents by neutron techniques. In this paper, neutron techniques - in particular, small angle neutron scattering SANS and neutron diffraction ND - are considered for the non-destructive characterization of Nitinol artery stents.

Nitinol self-expanding artery stents, as permanent vascular support structures, supply an ideal option to bypass surgery, but they are submitted for the whole of patient's life to the dynamical stress of the artery pulsation and the aggression from the biological environment. These stents, consequently, can suffer from wear and fracture occurrence likely due to a variety of cyclic fatigue, overload conditions and residual stresses.

Neutrons have recently become a progressively more important probe for various materials and components and they allow achieving information complementary to those obtained from the traditional microstructural analyses. The outputs from the preliminary works already carried out in this field consent to consider neutron techniques capable to contribute to the development of these crucial medical implants. The achievable results can yield trends adoptable in monitoring of the stent features.

Adhesion, vitality and osteogenic differentiation capacity of adipose derived stem cells seeded on nitinol nanoparticle coatings. Full Text Available Autologous cells can be used for a bioactivation of osteoimplants to enhance osseointegration.

In this regard, adipose derived stem cells ASCs offer interesting perspectives in implantology because they are fast and easy to isolate. However, not all materials licensed for bone implants are equally suited for cell adhesion. Surface modifications are under investigation to promote cytocompatibility and cell growth. The presented study focused on influences of a Nitinol -nanoparticle coating on ASCs. Possible toxic effects as well as influences on the osteogenic differentiation potential of ASCs were evaluated by viability assays, scanning electron microscopy, immunofluorescence and alizarin red staining.

It was previously shown that Nitinol -nanoparticles exert no cell toxic effects to ASCs either in soluble form or as surface coating. Here we could demonstrate that a Nitinol -nanoparticle surface coating enhances cell adherence and growth on Nitinol -surfaces. No negative influence on the osteogenic differentiation was observed.

Nitinol -nanoparticle coatings offer new possibilities in implantology research regarding bioactivation by autologous ASCs, respectively enhancement of surface attraction to cells. Physical properties of a new type of self-expandable nitinol stent. To study the new physical properties including hoop strength and flexibility of a newly developed nitinol stent.

The new stent was made of a single nitinol wire 0. This was wound around a cylindrical metallic jig with a constant angle to the longitudinal direction, and stents which winding were constructed. Hoop strength of the stents was measured with a spring gauge and compared with that of Wallstent and Hanaro stents.

The flexibility of the new stent was evaluated on the basis of changes in stent diameter when bent in the direction of deg Hoop strength of the new nitinol stent was proportional to 3. A greater number of wires on a lateral cut surface or a greater number of longitudinal windings also resulted in increased strength.

However, the former caused an increase in total wire area and the latter resulted increased stent length when compressed. Hoop strength of the new nitinol stent was superior to that of Wallstent and Hanaro stents, and stent diameter did not decrease when the stent was bent in the direction of degrees. Hoop strength of the new nitinol stent was most significantly affected by wire thickness.

The stent was very flexible and thus seemed suitable for an angled lumen. Passive base isolation with superelastic nitinol SMA helical springs. Seismic isolation of structures such as multi-story buildings, nuclear reactors, bridges, and liquid storage tanks should be designed to preserve structural integrity.

By implementing seismic isolation technology, the deformation of superstructures can be dramatically reduced, consequently helping to protect their safety as well. In this paper, an innovative type of passive base isolation system, which is mainly composed of superelastic nitinol SMA helical springs, is developed.

In order to verify the effectiveness of the proposed system, a two-story experimental steel frame model is constructed, and two superelastic SMA helical springs are thermo-mechanically built in the laboratory. To describe the nonlinear mechanical properties of the superelastic SMA helical springs under reciprocating load, a phenomenological model is presented in terms of a series of tensile tests. Afterwards, a numerical model of the two-story frame with the suggested isolation system is set up to simulate the response of the isolated frame subjected to an earthquake.

Both the experimental and the numerical simulation results indicate that the proposed base isolation system can remarkably suppress structural vibrations and has improved isolation effects when compared with a steel spring isolation system. Due to the capabilities of energy dissipation as well as fully re-centering, it is very applicable to utilize the suggested isolation system in base isolated structures to resist earthquakes. Nitinol stents in the treatment of benign proximal tracheal stenosis or tracheomalacia.

Nitinol stents have been used in the treatment of benign tracheal stenosis. A retrospective review of five patients treated at Stobhill Hospital over the last six and a half years is presented. Age at presentation ranged from 17 to 76 years. The minimum follow-up period was 23 months and the maximum was 78 months. All our patients were successfully decannulated, with none requiring recannulation.

Four patients developed granulation tissue related to the stent at intervals ranging from three weeks to 41 months post stenting. Topical mitomycin C application has been useful after resection of granulations using the carbon dioxide CO2 laser. Stent migration occurred in one patient three weeks after insertion. Nitinol stents are easy to insert and effective in the treatment of tracheal stenosis, but can have associated morbidity.

Their use should be considered carefully, as insertion should be regarded as permanent. Publications reporting experience and outcome with the use of Nitinol stents in the trachea are reviewed. To evaluate the patency and the freedom of target lesion revascularization of the 4-French Pulsar self-expandable SE nitinol stent for the treatment of long femoropopliteal occlusive disease in a two-center, prospective, all-comers registry with a follow-up period of 12 months.

This registry enrolled 36 patients with symptomatic femoropopliteal long lesions for recanalization and implantation of the 4-French Pulsar SE nitinol stent. Routine follow-up examination including duplex ultrasound was performed after 6 and 12 months. Primary patency was defined as no binary restenosis on duplex ultrasound Peak systolic velocitiy ration PSVR Pulsar SE nitinol stent for endovascular intervention of femoropopliteal disease with a mean lesion length of Diabetes and renal insufficiency had no negative impact on the patency rate.

Laser shape setting of superelastic nitinol wires: Functional properties and microstructure. Shape setting is one of the most important steps in the production route of Nitinol Shape Memory Alloys SMAs , as it can fix the functional properties, such as the shape memory effect and the superelasticity SE. In this work, a laser beam was adopted for performing straight shape setting on commercially available austenitic Nitinol thin wires.

The laser beam, at different power levels, was moved along the wire length for inducing the functional performances. Calorimetric, pseudo-elastic and microstructural features of the laser annealed wires were studied through differential scanning calorimetry, tensile testing and high energy X-ray diffraction, respectively. It can be stated that the laser technology can induce SE in thin Nitinol wires: the wire performances can be modulated in function of the laser power and improved functional properties can be obtained.

Simon nitinol vena cava filters: effectiveness and complications. Purpose: The aim of this retrospective analysis was to evaluate the clinical safety and effectiveness of the simon nitinol inferior vena cava filter SNF for prevention of pulmonary embolism. Patients and Methods: patients 63 male, 54 female; aged Patient reports were retrospectively analysed for complications during and after implantation and deep venous thrombosis DVT and pulmonary embolism before and after implantation.

Helical-CT with contrast media and plain abdominal radiography were performed on 35 patients, helical-CT alone on two patients. We checked the position and configuration of the SNF and looked for a perforation of the filter legs through the wall of the inferior vena cava IVC. The IVC and deep pelvic veins were analysed for patency. There was no significant increase in thrombosis of the deep pelvic veins and the IVC after implantation.

Pulmonary re-embolism PE was documented in 9 out of patients 7. One out of the 35 examined patients 2. Dislocation of the SNF more than 10 mm occurred in one out of 35 patients 2. We found no occlusion of the IVC. Laser-assisted fixation of a nitinol stapes prosthesis.

Otosclerosis is an inner ear bone disease characterized by fixation of the stapes and consequently progressive hearing loss. One treatment option is the surgical replacement of the stapes by a prosthesis. When so called "smart materials" like nitinol are used, prosthesis fixation can be performed using a laser without manual crimping on the incus. However, specific laser-prosthesis interactions have not been described yet. Total energy for closure was determined. Suitable laser parameters pulse duration, power per pulse, distance between tip of the laser fiber and prosthesis were assessed.

Specific laser-prosthesis interactions were recorded. Especially the diode laser was found to be an appropriate energy source. Energy should be transmitted through a laser fiber equipollent to the prosthesis band diameter. Specific deformation characteristics due to the zonal prosthesis composition have to be taken into account. Lasers Surg. A year-old woman presented with a large femoropopliteal aneurysm. A covered nitinol stent was implanted successfully and complete exclusion of the aneurysm was achieved.

At follow-up 5 months later the stent was still patent and the patient was free of symptoms. However, moderate stenosis was seen at the proximal end of the stent. This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents.

The research is aimed at addressing two of the primary failure modes in Nitinol endovascular stents: fatigue-crack growth and overload fracture. The small dimensions of stents, coupled with their complex geometries and variability among manufacturers, make it virtually impossible to determine generic material constants associated with specific devices. Instead, the research utilizes a hybrid of standard test techniques fracture mechanics and x-ray micro-diffraction and custom-designed testing apparatus for the determination of the fracture properties of specimens that are suitable representations of self-expanding Nitinol stents.

Specifically, the role of texture crystallographic alignment of atoms and the austenite-to-martensite phase transformation on the propagation of cracks in Nitinol was evaluated under simulated body conditions and over a multitude of stresses and strains. Statistical characteristics of surface integrity by fiber laser cutting of Nitinol vascular stents. Laser cutting is the dominant process for manufacturing Nitinol stents.

Conventional laser cutting usually produces unsatisfactory surface integrity which has a significant detrimental impact on stent performance. Emerging as a competitive process, fiber laser with high beam quality is expected to produce much less thermal damage such as striation, dross, heat affected zone HAZ , and recast layer. To understand the process capability of fiber laser cutting of Nitinol alloy, a design-of-experiment based laser cutting experiment was performed.

The kerf geometry, roughness, topography, microstructure, and hardness were studied to better understand the nature of the HAZ and recast layer in fiber laser cutting. Moreover, effect size analysis was conducted to investigate the relationship between surface integrity and process parameters. Fu, C. Use of nitinol self-expandable stents in 26 dogs with tracheal collapse. A study was designed to describe a novel approach to the treatment of tracheal collapse TC in dogs using self-expandable nitinol stents.

Medical records were reviewed retrospectively for 26 client owned dogs in which nitinol stents were deployed. The entire length of trachea was supported independently of the extent of TC. Two overlapping stents were used instead of one in cases where one stent was not spanning the entire trachea adequately.

The diameter of the cranial radiolucent portion of trachea, just behind the cricoid cartilage, was measured as a specific landmark to select the appropriate size of the stent. Two self-expandable nitinol stents were inserted in 9 of 26 dogs; the trachea in the rest of the cases was supported with only one stent. A follow up tracheoscopy was performed in 10 of 26 cases with recurrent clinical signs.

Secondary tracheal stenosis in these cases was caused by stent fracture, granuloma or excessive stent shortening. Additional stents were placed successfully to expand the stenotic lumen. A support of the entire trachea may decrease risk of nitinol fracture at the end of the implant. Multiscale electrochemical analysis of the corrosion of titanium and nitinol for implant applications.

Izquierdo, J. SECM was operated in feedback and redox competition modes as a function of potential applied to the substrate. The kinetics of the electron transfer rate on both materials was characterized by mathematical modelling of the Z-approach curves monitored under feedback conditions.

The rate constant values greatly depended on the characteristics of the passive layers formed over the metals under potentiostatic control. A more insulating film was found on nitinol when biased at low polarizations, resulting in smaller tip current increments during tip approach to the investigated surface under positive feedback and competition operation modes.

However, at higher anodic polarizations, nitinol passive layers experience breakdown, and therefore tip current values reflect the release of metal cations from the biomaterial surface. Materials and Methods. Eighteen patients underwent PTA of focal atherosclerotic occlusive disease of distal abdominal aorta.

Two symptomatic occlusions and 16 stenoses in 10 male and 8 female patients mean age No complications associated with the procedure occurred. During the Endovascular treatment primary self-expandable nitinol stent placement of focal atherosclerotic lesions of distal abdominal aorta is a safe method with excellent primary technical and clinical success rates and favourable Long term results. In that evaluation, most specimens were exposed for a year.

Nitinol 60 was added to the test program in High-resolution 3D X-ray imaging of intracranial nitinol stents. Snoeren, Rudolph M. To assess an optimized 3D imaging protocol for intracranial nitinol stents in 3D C-arm flat detector imaging. For this purpose, an image quality simulation and an in vitro study was carried out.

Nitinol stents of various brands were placed inside an anthropomorphic head phantom, using iodine contrast. Experiments with objects were preceded by image quality and dose simulations. We varied X-ray imaging parameters in a commercially interventional X-ray system to set 3D image quality in the contrast-noise-sharpness space. Beam quality was varied to evaluate contrast of the stents while keeping absorbed dose below recommended values. Two detector formats were used, paired with an appropriate pixel size and X-ray focus size.

Zoomed reconstructions were carried out and snapshot images acquired. High contrast spatial resolution was assessed with a CT phantom. We found an optimal protocol for imaging intracranial nitinol stents. Contrast resolution was optimized for nickel-titanium-containing stents. A high spatial resolution larger than 2. We obtained images of stents of various brands and a representative set of images is shown. Independent of the make, struts can be imaged with virtually continuous strokes.

By balancing the modulation transfer of the imaging components and tuning the high-contrast imaging capabilities, we have shown that thin nitinol stent wires can be reconstructed with high contrast-to-noise ratio and good detail, while keeping radiation doses within recommended values. Experimental results compare well with imaging simulations. Treatment of malignant gastroduodenal obstruction with using a newly designed complex expandable nitinol stent: initial experiences. We wanted to evaluate the usefulness of a new type of a complex expandable nitinol stent that was designed to reduce the stent's propensity to migration during the treatment of malignant gastroduodenal obstructions.

Two types of expandable nitinol stent were constructed by weaving a single thread of 0. Both ends of the covered stent were fabricated by coaxially inserting the covered stent into the tubular uncovered stent and then attaching the two stents together with using nylon monofilament. Clinical improvement was assessed by comparing the food intake capacity before and after the procedure.

The complications were investigated during the follow up period. Stent placement was successful in all the patients. After stent placement, the symptoms improved in all but one patient. Despite the stent migration, the patient was able to resume a soft diet. Six patients developed recurrent symptoms of obstruction with tumor overgrowth at a mean of days after the procedure; all the patients underwent coaxial placement of an additional stent with good results. One patient showed recurrence of obstruction due to tumor in-growth, and this was treated by placement of a second stent.

Two patients with stent placement in the duodenum suffered from jaundice 26 days and 65 days, respectively, after their procedures. Placement of the newly designed complex expandable nitinol stent seems to be effective for the palliative treatment of malignant gastroduodenal obstructions. The new stent also seems to help overcome the.

Management of stent dislodgment in coarctoplasty of aorta with three overlapping self-expandable nitinol stents. We describe a case of native coarctation of aorta managed with three self-expandable nitinol stents. After balloon pre-dilation, the first and second stents were dislodged. The coarcted area was successfully treated with the third stent overlapped with the previous stents. During follow up 30 months , the patient was free of complications.

It seems that implantation of multiple overlapping self-expandable stents in aortic coarctation patients, if needed, is safe and possible. Full Text Available This paper presents nano-impact low cycle fatigue behavior of as-deposited amorphous nitinol TiNi thin film deposited on Si wafer. The nitinol film was 3. Each nano-impact test was conducted for a total of fatigue cycles. Depth sensing approach was adapted to understand the mechanisms of film failure.

Based on the depth-time data and surface observations of films using atomic force microscope, it is concluded that the shape of the indenter test probe is critical in inducing the localized indentation stress and film failure. The measurement technique proposed in this paper can be used to optimize the design of nitinol thin films.

Transcatheter aortic value implantation with self-expandable nitinol valved stent: an experimental study in sheep. Objective: to determine the feasibility and safety of transcatheter aortic valve implantation with domestic self-expandable nitinol valved stent in experimental sheep. Methods: A fresh pig pericardium was cross-linked with a 0.

Ten healthy sheep of Under general anesthesia, the device was delivered through catheter into the native aortic valve of the sheep via the femoral artery or abdominal aorta. The animals were followed up for three months. Results: Six devices were successfully delivered at the desired position in six sheep with no occurrence of complications. Angiographic and hemodynamic studies confirmed that the stents were fixed at correct position with competent valve function immediately and 90 days after the procedure.

Technical failure or fatal complications occurred in the remaining four sheep. Conclusion: Implantation of a domestic nitinol self-expandable stent at the aortic valve position through a transcatheter approach is feasible in experimental sheep. Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease PAD due to its minimally invasive nature and associated reductions in short-term morbidity and mortality.

The mechanical properties of the superelastic Nitinol alloy have played a major role in the explosion of peripheral artery stenting, with modern stents demonstrating reasonable resilience and durability. Yet in the superficial femoral and popliteal arteries, even the newest generation Nitinol stents continue to demonstrate clinical outcomes that leave significant room for improvement.

Restenosis and progression of native arterial disease often lead to recurrence of symptoms and reinterventions that increase morbidity and health care expenditures. One of the main factors thought to be associated with stent failure in the femoropopliteal artery FPA is the unique and highly dynamic mechanical environment of the lower limb. Clinical and experimental data demonstrate that the FPA undergoes significant deformations with limb flexion. It is hypothesized that the inability of many existing stent designs to conform to these deformations likely plays a role in reconstruction failure, as repetitive movements of the leg and thigh combine with mechanical mismatch between the artery and the stent and result in mechanical damage to both the artery and the stent.

In this review we will identify challenges and provide a mechanical perspective of FPA stenting, and then discuss current research directions with promise to provide a better understanding of Nitinol , specific features of stent design, and improved characterization of the biomechanical environment of the FPA to facilitate development of better stents for patients with PAD. Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties.

The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential.

However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life.

Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials.

Purpose: To evaluate the immediate and long-term results in ten patients with malignant biliary obstruction using a polyurethane-covered, self-expandable nitinol stent. Methods: A nitinol stent, fully covered with high-elasticity polyurethane, with an unconstrained diameter of 10 mm and a total length of mm, was placed transhepatically under fluoroscopic guidance in ten patients.

The length of the biliary obstruction varied between mm. The follow-up examination included a clinical assessment, serum bilirubin measurement, and ultrasound examinations at one-month intervals in all patients. Results: Initial stent deployment was successful in eight patients. Two patients experienced proximal migration,which was solved by insertion of two, uncovered Wallstents. One patient had the stent removed after two weeks because of severe nausea and vomiting.

One patient had delayed migration of the covered stent after 40 weeks. The follow-up duration was weeks Mean: Seven patients died weeks and three patients survived weeks. The bilirubin measurements in all patients had significantly decreased one week after stent insertion. The levels of amylase and lipase had did not increase after stent insertion.

Conclusions: Apolyurethane-covered, self-expandable nitinol stent can be used effectively and safely in the treatment of malignant biliary obstruction. The preliminary results are favorable, but there is a need for further large studies to determine both long-term survival and patency. Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease PAD due to its minimally invasive nature and associated reductions in short-termmorbidity and mortality.

We wanted to determine the technical and clinical efficacy of using a PTFE-covered self-expandable nitinol stent for the palliative treatment of malignant biliary obstruction. Thirty-seven patients with common bile duct strictures caused by malignant disease were treated by placing a total of 37 nitinol PTFE stents.

These stents were covered with PTFE with the exception of the last 5 mm at each end; the stent had an unconstrained diameter of 10 mm and a total length of 50 80 mm. The patient survival rate and stent patency rate were calculated by performing Kaplan-Meier survival analysis. The bilirubin, serum amylase and lipase levels before and after stent placement were measured and then compared using a Wilcoxon signed-rank test.

The average follow-up duration was Placement was successful in all cases. There were no immediate complications. Three patients demonstrated stent sludge occlusion that required PTBD percutaneous transhepatic biliary drainage irrigation. Two patients experienced delayed stent migration with stone formation at 7 and 27 weeks of follow-up, respectively. The bilirubin levels were significantly reduced one week after stent insertion p nitinol stent is safe to use with acceptable complication rates.

This study is similar to the previous studies with regard to comparing the patency rates and survival rates. Self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty. The feasibility of self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty was assessed.

Options for lower limb percutaneous revascularization are limited, especially for complex vessel obstruction. Until recently, no self-expanding stent for the use in the infragenicular arteries was available. This is the first report of the results for 18 consecutive patients who received 4F sheath compatible self-expanding nitinol stents following unsuccessful PTA or early restenosis.

Stent implantation was feasible in all cases. No complications occurred. At follow-up, the patency could be assessed in 14 stented arteries. The use of self-expanding nitinol stents in tibioperoneal and popliteal arteries is a safe and feasible option for the treatment of unsuccessful PTA. The 6-months patency is high. A patient suffering from esophagorespiratory fistula after bougienage of a benign stricture at the site of the anastomosis between a jejunal interposition and the esophagus was referred for interventional treatment.

A prototype nitinol stent centrally covered with Dacron was implanted under regional anesthesia and fluoroscopic guidance. The self-expanding prosthesis dilated the stenosis completely and closed the fistula, with consequent improvement in respiratory and nutritional status and thus the general quality of life. The patient was able to eat and drink normally until death 3 months later due to progression of his underlying malignant disease.

Specimens of 60 NiTi were heat treated in air at degC for 30 min or 2 hr, then quench cooled by one of seven different methods. The microstructure and hardness of this material was examined post heat treatment. The results indicated that the quench method had little effect on the resulting hardness and microstructure of 60 NiTi. To retrospectively review the patency of endovascular interventions with nitinol stent placement for symptomatic central venous occlusions in hemodialysis patients.

A retrospective review of all patients who underwent endovascular interventions for dysfunctional hemodialysis grafts and fistulas was performed from April to August The study group consisted of 3 men and 3 women with a mean age of Of these 6 patients, 1 had a graft and 5 had fistulas in the left arm. The primary indication for nitinol stent placement was technical failure of angioplasty following successful traversal of occluded central venous segments.

Patency was assessed from repeat fistulograms and central venograms performed when patients redeveloped symptoms or were referred for access dysfunction determined by the ultrasound dilution technique. No patients were lost to follow-up. In 1 patient, incorrect stent positioning resulted in partial migration to the superior vena cava requiring restenting to prevent further migration.

Over the follow-up period, 2 patients underwent repeat intervention with angioplasty alone. Primary patency was Mean primary patency was No complications related to recanalization of the occluded central venous segments were observed. Our initial experience has demonstrated that use of nitinol stents for central venous occlusion in hemodialysis patients is. Surface modification and fatigue behavior of nitinol for load bearing implants. Musculoskeletal disorders are recognized amongst the most significant human health problems that exist today.

Even though considerable research and development has gone towards understanding musculoskeletal disorders, there is still lack of bone replacement materials that are appropriate for restoring lost structures and functions, particularly for load-bearing applications.

Many materials on the market today, such as titanium and stainless steel, suffer from significantly higher modulus than natural bone and low bioactivity leading to stress shielding and implant loosening over longer time use. Nitinol NiTi is an equiatomic intermetallic compound of nickel and titanium whose unique biomechanical and biological properties contributed to its increasing use as a biomaterial.

An innovative method for creating dense and porous net shape NiTi alloy parts has been developed to improve biological properties while maintaining comparable or better mechanical properties than commercial materials that are currently in use.

Porous implants are known to promote cell adhesion and have a low elastic modulus, a combination that can significantly increase the life of an implant. However, porosity can significantly reduce the fatigue life of an implant, and very little work has been reported on the fatigue behavior of bulk porous metals, specifically on porous nitinol alloy. In cyclic compression loading, plastic strain increased with increasing porosity and it was evident that maximum strain was achieved during the first cycles and remained constant throughout the remaining loading.

When subjected. Predictive parameters for fistula healing using this technique remain uncertain. Comparison of visibility for four self-expanding nitinol bare stents in vitro. Background Sufficient radiopacity of stents is a prerequisite for safe interventions and minimization of the radiation dose for the patient and the interventionist.

Modern nitinol stents are considered less radiopaque compared to formerly used stents. Purpose To evaluate the objective detection rate ODR and the subjective radiopacity score SRS of four self-expanding nitinol stents with their markers on a phantom human pelvis. Stents were placed on a phantom human pelvis and images of the stents were taken in four different positions right and left lumbosacral joint and near the right and left limbus acetabuli using the following modes: spotfilm, pulsed fluoroscopy 4, 7.

Dose area products DAPs were assessed. On phase transformation models for thermo-mechanically coupled response of Nitinol. Fully coupled thermomechanical models for Nitinol at the grain level are developed in this work to capture the inter-dependence between deformation and temperature under non-isothermal conditions. The martensite transformation equations are solved using a novel algorithm which imposes all relevant constraints on the volume fractions.

The numerical implementation of the resulting models within the finite element method is effected by the monolithic solution of the momentum and energy equations. Validation of the models is achieved by means of thin-tube experiments at different strain rates.

Polyorethaoe-covered nitinol strecker stents as primary palliative treatment of malignant biliary obstruction. Purpose: To evaluate the clinical efficacy of the polyure-thane-covered Nitinol Strecker stent in the treatment of patients with malignant biliary obstruction. Methods: Twenty-three covered stents produced by us were placed in 18 patients with malignant biliary obstruction. Resulrs: The mean patency period of the Stents was Adequate biliary drainage over 50 weeks or until death was achieved in 17 of 18 patients Late cholangitis was observed in two patients whose stents bridged the ampulla of Vater.

Other late severe complications were not encountered. Conclusion: Although more study is necessary, our results suggest the clinical efficacy of our covered Nitinol Strecker stent in the management of obstructive jaundice caused by malignant diseases.

Nitinol alloys have been used in various biological applications due to their superior properties. In this study, a bipolar pulsed current electrodeposition technique was applied to produce a hydroxyapatite HA film on the Nitinol alloy. Also, the protection performance of the coating was evaluated on both abraded and thermochemically modified alloy. According to obtained data, reducing the electrocrystallization rate by the pulse deposition technique can promote HA formation on both abraded and modified substrates.

Based on scanning electron microscopy and high-resolution transmission electron microscopy data, the HA coatings revealed a flake-like morphology and each flake was composed of nano-crystalline grains. Atomic force microscopy images revealed that flakes on the abraded substrate were smaller in size than that of the modified alloy. Comparing the corrosion resistance of the bare substrates revealed that the modified alloy has a higher corrosion resistance than the abraded alloy and the modified surface is well passivized during anodic polarization in Ringer's solution.

However, this condition is reversed after the deposition of HA film. It seems that because of the lower crystallization sites on the abraded alloy, the produced HA film is denser and more protective against the corrosive mediums as compared to the coating on the modified alloy. Although the HA coating can improve the bioactivity of both substrates, the resulted film on the oxidized alloy is porous and deteriorates the implant permanence in the vicinity of body fluids.

Sesterhenn, Andreas M. We assessed the results of self-expanding metallic stent insertion into benign proximal tracheal stenosis in patients not appropriate or unfit for surgical repair. Proximal benign tracheal stenoses had occurred in 11 patients 7 men, 4 women, mean age Fourteen self-expanding nitinol stents were placed in the patients under general anesthesia with endoscopical and fluoroscopical guidance.

Stent insertion was successful in all cases and led to immediate relief of the morphological and functional airway obstruction. No immediate complications were noted. During the mean follow-up period of Both complications were successfully treated with additional stent insertion in one case and laser resection of granulomas in the other.

Self-expanding nitinol stents should be considered for the treatment of benign proximal tracheal obstruction in selected patients for whom surgical repair is contraindicated. Biomedical engineering in design and application of nitinol stents with shape memory effect. Our studies in the field of endosurgery in collaboration with the physicians of the National Research Center of Surgery of the Academy of Medical Sciences are carried out beginning in These studies laid the foundation for the new direction of X-ray surgery--X-ray Nitinol stenting of vessels and tubular structures.

X-ray nitinol stents are unique self-fixing shells based on the shape memory effect and superelasticity of nickel-titanium alloys self- reconstructed under human body temperature. Applied for stenting of arteries in cases of stenosis etc. The purpose of stenting is restoration of the shape of artery or tubular structure by a cylinder frame formation. The especially elaborated original method of stenting allows to avoid the traditional surgical operation, i.

The stent to be implanted is transported into the affected zone through the puncture under the X-ray control. Clinical applications of X-ray endovascular stenting has been started in March During this period nearly operations on stenting have been performed on femoral, iliac, brachio-cephalic, subclavian arteries, bile ducts, tracheas, digestive tract and cervical canal uterus.

Wireless implantable chip with integrated nitinol -based pump for radio-controlled local drug delivery. We demonstrate an active, implantable drug delivery device embedded with a microfluidic pump that is driven by a radio-controlled actuator for temporal drug delivery. The rectangular-shaped spiral-coil actuator based on nitinol , a biocompatible shape-memory alloy, is developed to perform cantilever-like actuation for pumping operation.

The nitinol -coil actuator itself forms a passive MHz resonant circuit that serves as a self-heat source activated via RF power transfer to enable frequency-selective actuation and pumping. Experimental wireless operation of fabricated prototypes shows successful release of test agents from the devices placed in liquid and excited by radiating tuned RF fields with an output power of 1. The thermal behavior of the activated device is also reported in detail. This proof-of-concept prototype validates the effectiveness of wireless RF pumping for fully controlled, long-lasting drug delivery, a key step towards enabling patient-tailored, targeted local drug delivery through highly miniaturized implants.

Nitinol laser cutting: microstructure and functional properties of femtosecond and continuous wave laser processing. Thermal processing can affect the properties of smart materials, and the correct selection of the best manufacturing technology is fundamental for producing high tech smart devices, containing embedded functional properties. In this work cutting of thin superelastic Nitinol plates using a femtosecond fs and continuous wave CW laser was studied.

Diamond shaped elements were cut to characterize the kerf qualitative features; microstructural analysis of the cross sections allowed identification of thermal damage characteristics introduced into the material during the laser processes. Obtaining samples that remain superelastic and exhibit desired precurvatures currently requires many iterations, which is time consuming and consumes a substantial amount of Nitinol. To provide a more accurate and reliable method of shape setting, in this paper we propose an electrical technique that uses Joule heating to attain the necessary shape setting temperatures.

The resulting high power heating prevents unintended aging of the material and yields consistent and accurate results for the rapid creation of prototypes. We present a complete algorithm and system together with an experimental analysis of temperature regulation. We experimentally validate the approach on Nitinol tubes that are shape set into planar curves.

We also demonstrate the feasibility of creating general space curves by shape setting a helical tube. Unstable fractures and nonunion of the middle third of the scaphoid, which need open reduction and internal fixation from palmar. The staples can only be used, if the arms of the staples can be inserted parallel to and at a distance of 3 mm to the fracture line.

Allergy to nickel. Cases in which the arms of the staple cannot be inserted parallel to and at best 3 mm apart from the fracture line. In fractures, open reduction of the scaphoid through a palmar approach. If necessary, interposition of a bone graft and Kirschner wire transfixation. Drilling of the drill holes parallel and at a distance of 3 mm to the fracture line.

In nonunion, excision of the fibrous nonunion, refreshening of the fracture surfaces, interposition of a bone graft and, if needed, fixation with a Kirschner wire. Within a few minutes the warming-up staple contracts and thereby compresses the scaphoid.

Immobilization in a short cast with thumb support for 6 weeks. Control for bone healing by radiographs or computed tomography. Staples, which do not cause hardware problems, are not removed. Kirschner wires are removed after bone healing. Indications were 15 unstable fractures, 47 nonunions, and three partial necroses. Seven staples were removed, one for loosening.

NITINOL shape memory staples have proven to be very helpful for osteosynthesis in fractures and nonunion of the scaphoid, if the prerequisites are given for their use. Strecker degradation SD leading to the formation of phenylacetaldehyde PA was studied in wine systems.

New insights were gained by using two full factorial designs focusing on the effects of 1 pH and 2 temperature. In each design of experiments DoE three factors, glucose, gallic acid, and metals at two levels present or absence , were varied while phenylalanine was kept constant.

In fact, kinetics results showed that the presence of glucose had an inhibitory effect on PA rate of formation. By gallic acid quinone quantitation it is shown that glucose affects directly the concentration of the quinone. This highlights the role of sugar in o-quinone concentration and consequently in the impact on Strecker aldehyde formation, a promising new perspective regarding wine shelf-life understanding.

The effects of Nitinol phases on corrosion and fatigue behavior. The purpose of these studies was to provide a detailed understanding of Nitinol phases and their effects on corrosion and fatigue life. The two primary phases, austenite and martensite, were carefully evaluated with respect to material geometry, corrosion behavior, wear, and fatigue life. Uniaxial tensile tests were conducted to determine the mechanical properties such as elongation, ultimate tensile strength, modulus, transformation strain, and plateau stress.

In addition, accelerated wear testing and four point bend fatigue testing were completed to study the fatigue life and durability of the material. The corrosion of Nitinol was found to be dependent on various surface conditions. Electrochemical corrosion behavior of each phase was investigated using cyclic potentiodyamic polarization testing. The corrosion response of electropolished Nitinol was found to be acceptable, even after durability testing. Stress-induced martensite had a lower breakdown potential due to a rougher surface morphology, while thermally induced martensite and austenite performed similarly well.

The surface conditioning also had a significant effect on Nitinol mechanical properties. Electropolishing provided a smooth mirror finish that reduced localized texture and enhanced the ductility of the material. Quasi-static mechanical properties can be good indicators of fatigue life, but further fatigue testing revealed that phase transformations had an important role as well. The governing mechanisms for the fatigue life of Nitinol were determined to be both martesitic phase transformations and surface defects.

A new ultimate dislocation strain model was proposed based on specific accelerated step-strain testing. Endoscopically placed nitinol stents for pediatric tracheal obstruction. To provide preliminary clinical data regarding endoscopically placed nitinol stents for children with tracheal obstruction as a temporizing measure to allow for trach tube decannulation while awaiting growth to allow for tracheal resection.

This case series describes the experiences of two children ages 5 and 15 who were dependent upon tracheotomy because of acquired tracheal obstruction. Both patients had combined tracheomalacia and tracheal stenosis. After failing tracheoplasty with rib graft augmentation both patients suffered from extensive tracheal disease, which was too long to allow for immediate tracheal resection.

Endoscopic placement of nitinol stents in the obstructed tracheal segment using fluoroscopic guidance. All tracheotomy tubes were removed immediately after successful stent deployment with the patient still under general anesthesia. Four stents were placed in total. The first patient's initial stent was too narrow and was, therefore, removed and replaced at a later date with a larger diameter stent.

The second patient experienced distal migration of his initial stent requiring stent removal and replacement at a later date. Both patients remain successfully decannulated follow-up, 25 and 26 months and are currently living more normal lives as they grow and await tracheal resection. Preliminary use of nitinol stents for pediatric tracheal obstruction has enabled successful decannulation in two children with complicated airways. Our results with this series of patients suggest that nitinol stents can be safely used in children as a temporizing measure until tracheal resection can be safely performed.

With this approach children can live free from the hassles of trach care, social isolation and peer ridicule. Limited pediatric experience exists in the literature about nitinol stents. Thus, our experience with stent selection and placement will help others avoid problems encountered in this initial series. Copyright Elsevier Science Ireland. Full Text Available In this study, the interaction between the Nitinol stent and the artery with plaque was investigated using finite element method.

The occurring pressure values during the cardiac contraction systolic and loosening diastolic were applied as loading to the modeled system with Nitinol stent. In the light of the stress values, the suitability of the Nitinol stent in an artery with plaque was investigated. In the analysis, Nitinol stent was assumed to be shape memory alloy, and artery and plaque were assumed to behave linearly elastic. As a result, the stress and deformations in the plaque and artery due to the interference of Nitinol stent were discussed and concluded that the structure of artery with plaque can be expanded in accordance with Nitinol stent.

The corrosion resistance of Nitinol alloy in simulated physiological solutions. The corrosion behaviour of Nitinol alloy containing nearly equi-atomic composition of nickel and titanium and its constituent metals nickel and titanium was investigated in simulated Hanks physiological solution pH value 7. In this chloride-rich medium the corrosion stability of Nitinol is limited by the susceptibility to localized corrosion and is in that sense more similar to nickel than to titanium.

The corrosion stability of Nitinol is strongly dependent on the surface preparation—grinding, polishing or chemical etching. Whereas a ground surface is not resistant to localized corrosion, polished and chemically etched surfaces are resistant to this type of corrosion attack. The reasons for this behaviour were investigated through metallurgical, topographical and chemical properties of the surface as a function of surface preparation.

For that purpose, scanning electron microscopy combined with chemical analysis, confocal microscopy and X-ray photoelectron spectroscopy were used. Besides differences in topography, distinct differences in the chemical composition of the outermost surface are observed. Ground, rough surfaces comprised mainly titanium oxides and small amounts of nickel metal. Chemically etched and, especially, polished surfaces are composed of a mixture of titanium, nickel and titanium oxides, as studied by angle resolved X-ray photoelectron spectroscopy.

These results emphasize the importance of detailed investigation of the metal surface since small differences in surface preparation may induce large differences in corrosion stability of material when exposed to corrosive environments. The hardness and microstructure of twenty-six binary and ternary Nitinol nickel titanium, nickel titanium hafnium, nickel titanium zirconium and nickel titanium tantalum compounds were studied.

A small 50g ingot of each compound was produced by vacuum arc remelting. Each ingot was homogenized in vacuum for 48 hr followed by furnace cooling. Specimens from the ingots were then heat treated at , , or degree C for 2 hr followed by water quenching. The hardness and microstructure of each specimen was compared to the baseline material Nitinol , 55 at. The results show that eleven of the studied compounds had higher hardness values than the baseline material.

Moreover, twelve of the studied compounds had measured hardness values greater HV at heat treatments from to degree C. Frequent wire breakage during electrical-discharge machining of this material was investigated. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage.

The results of this investigation highlight the importance of material cleanliness to its further implementation. Designing and simulating a nitinol -based micro ejector. Full Text Available This paper describes pico-droplet ejector design and simulation. These pico-liter ejectors could have applications in making, lubricating and cooling integrated circuits. The linear thermal expansion coefficient, specific heat capacity, electrical resistivity and thermal conductivity of NITINOL were studied over a range of temperatures representing the operating environment of an oil-lubricated bearing.

The behavior of this material appears to follow wellestablished theories applicable to either metal alloys, in general, or to intermetallic compounds, more specifically and the measured data were found to be comparable to those for conventional bearing alloys.

Purpose: To evaluate the clinical use of covered and noncovered, knitted nitinol stents in patients presenting new stent indications. Methods: Self-expandable, knitted nitinol stents were implanted in four patients for treatment of dysphagia.

In two patients who had malignant strictures and had esophago-respiratory fistulae and in one patient with an esophagocutaneous fistula, polytetrafluoroethylene PTFE -covered stents were implanted. One patient received a noncovered stent, but a retrograde approach through a percutaneous endoscopic gastrostomy PEG fistula had to be chosen for recanalization of an esophageal occlusion. Two patients received stents for treatment of benign strictures.

Results: Recanalization of the stricture and stent implantation were performed under fluoroscopic control without any procedure-related morbidity or mortality. Dysphagia improved in all patients and the esophageal fistulae could be sealed off by covered stents.

During a maximum follow-up of 18 months, there was no stent migration or esophageal perforation. Most complications could be treated by the interventional radiologist. Conclusion: Self-expandable, covered Nitinol stents provide an option for the treatment of dysphagia combined with esophageal fistulae. In combination with interventional radiology techniques, even complex strictures are accessible. For benign strictures, the value of stent treatment has not yet been proven.

Results of the new nitinol self-expandable stents for distal biliary structures. The nitinol stent is a self-expandable spiral stent made of nickel-titanium alloy. We performed a pilot study to evaluate the method of stent insertion and stent efficacy. Twenty-eight patients with irresectable malignancy had nitinol stents inserted for obstructive jaundice due to distal biliary.

Self-expandable nitinol stent placement in homocysteinemic porcine aorta. Full Text Available PURPOSE: To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs induced with a methionine-rich diet following placement of a self-expanding nitinol stent.

They were older than eight weeks in age and had an average weight of 30 kg. Pigs were randomly divided into two groups. The first, Group C control, was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia.

The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography.

Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis. When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M.

There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group. Monitorizing nitinol alloy surface reactions for biofouling studies. Dinu, C. Growth and deposition of unwanted bacteria on implant metal alloys affect their use as biomedical samples. Monitoring any bacterial biofilm accumulation will provide early countermeasures. For a reliable antifouling strategy we prepared nitinol NiTi thin films on Ti-derived substrates by using a pulsed laser deposition PLD method.

As the microstructure of Ti-alloy is dictated by the tensile strength, fatigue and the fracture toughness we tested the use of hydrogen as an alloying element. X-ray diffraction XRD , scanning electron microscopy SEM and atomic force microscopy AFM investigated the crystalline structure, chemical composition and respectively the surface morphology of the nitinol hydrogen and hydrogen-free samples.

Moreover, the alloys were integrated and tested using a cellular metric and their responses were systematic evaluated and quantified. Our attractive approach is meant to select the suitable components for an effective and trustworthy anti-fouling strategy. A greater understanding of such processes should lead to novel and effective control methods that would improve in the future implant stability and capabilities.

Fatigue of Nitinol : The state-of-the-art and ongoing challenges. Nitinol , a nearly equiatomic alloy of nickel and titanium, has been considered for a wide range of applications including medical and dental devices and implants as well as aerospace and automotive components and structures.

The realistic loading condition in many of these applications is cyclic; therefore, fatigue is often the main failure mode for such components and structures. The fatigue behavior of Nitinol involves many more complexities compared with traditional metal alloys arising from its uniqueness in material properties such as superelasticity and shape memory effects.

In this paper, a review of the present state-of-the-art on the fatigue behavior of superelastic Nitinol is presented. Various aspects of fatigue of Nitinol are discussed and microstructural effects are explained. Effects of material preparation and testing conditions are also reviewed. Finally, several conclusions are made and recommendations for future works are offered. The surface of Nitinol alloy was activated by a thermo-chemical treatment and hydroxyapatite coating was electrodeposited on the alloy, followed by applying the polymer coating.

The data revealed that the hydroxyapatite coating is composed of one-dimensional nano sized fl A torsional artificial muscle from twisted nitinol microwire. A work density of up to MPa can be achieved from these microwires.

In the present work, we are showing that by twisting the microwires in form of closed-loop two-ply yarn we can create a torsional actuator. We measured a gravimetric torque of up to These remarkable performance results are comparable to those of guest-infiltrated carbon nanotube twisted yarns. A previous paper Duerig and Bhattacharya in Shap Mem Superelasticity , introduced several engineering considerations surrounding the R-phase in Nitinol and highlighted a common, if not pervasive, misconception regarding the use of the term Af by the medical device industry.

This paper brings additional data to bear on the issue and proposes more accurate terminology. Moreover, a variety of tools are used to establish the forward and reverse stress-temperature phase diagrams for a superelastic wire typical of that used in medical devices. Once established, the two most common methods of measuring transformation temperatures, Differential Scanning Calorimetry and Bend Free Recovery, are tested against the observed behavior.

The use of silicone- or metal stents in stenosis of the distal trachea and the bronchial system is a customary procedure [], for example after tumor invasion or cicatricial stenosis after transplantation. In the proximal part of the trachea, on smaller, short and soft strictures we try to stabilise the trachea by the implantation of rings. Other methods are tracheal plasty or transverse tracheal resectomy [].

In the case of longer or nearer subglottal stenoses the positioning of self-expanding nitinol stents has proven a simple, gentle and well-tolerated alternative procedure even in very serious disorders [1, 8, 9]. These stents can be placed in short narcosis under endoscopic control without great strain on the patient.

We placed nitinol -stents in the proximal part of the trachea in eleven cases. In five cases dyspnoea caused by a tracheal collapse improved. In two further cases a tracheal stenosis with massive granulation tissue and cicatricial pull under an inlaid tracheal cannula was removed and the tracheostoma was closed.

In four cases a solid, scarred and cartilaginous stenosis in the area of the cricoid and the upper tracheal rings was widened with laser and later on stented. Over an observation time of two years no complications showed safe one case in which a directly postoperative dislocation was repositioned quickly.

The patients live without restrictions through the tracheal stenosis or a tracheostoma. In the best possible case epithelialization over the metal meshes develops so that a nearly normal mucus transportation is possible [1, ]. The widespread acceptance of carotid artery stenting CAS to treat carotid artery stenosis and its effectiveness compared with surgical counterpart, carotid endarterectomy CEA , is still a matter of debate. Transient or permanent neurological deficits may develop in patients undergoing CAS due to distal embolization or hemodynamic changes.

Design, development, and usage of embolic protection devices EPDs , such as embolic protection filters, appear to have a significant impact on the success of CAS. Unfortunately, some drawbacks, such as filtering failure, inability to cross tortuous high-grade stenoses, malpositioning and vessel injury, still remain and require design improvement. Currently, many different designs of such devices are available on the rapidly growing dedicated market.

In spite of such a growing commercial interest, there is a significant need for design tools as well as for careful engineering investigations and design analyses of such nitinol devices. The present study aims to investigate the embolic protection filter design by finite element analysis. Subsequently, we used the finite element method to simulate the deployment of the nitinol filter as it exits the delivery sheath. Comparison of the simulations with micro-CT images of the real device exiting the catheter showed excellent correspondence with our simulations.

Finally, we evaluated circumferential basket-vessel wall apposition of a 4 mm size filter in a straight vessel of different sizes and shape. We conclude that the proposed methodology offers a useful tool to evaluate and to compare current or new designs of EPDs. Further simulations will investigate vessel wall apposition in a realistic tortuous anatomy.

Feasibility study for the investigation of Nitinol self-expanding stents by neutron techniques. In this paper, neutron techniques - in particular, small angle neutron scattering SANS and neutron diffraction ND - are considered for the non-destructive characterization of Nitinol artery stents. Nitinol self-expanding artery stents, as permanent vascular support structures, supply an ideal option to bypass surgery, but they are submitted for the whole of patient's life to the dynamical stress of the artery pulsation and the aggression from the biological environment.

These stents, consequently, can suffer from wear and fracture occurrence likely due to a variety of cyclic fatigue, overload conditions and residual stresses. Neutrons have recently become a progressively more important probe for various materials and components and they allow achieving information complementary to those obtained from the traditional microstructural analyses.

The outputs from the preliminary works already carried out in this field consent to consider neutron techniques capable to contribute to the development of these crucial medical implants. The achievable results can yield trends adoptable in monitoring of the stent features.

Adhesion, vitality and osteogenic differentiation capacity of adipose derived stem cells seeded on nitinol nanoparticle coatings. Full Text Available Autologous cells can be used for a bioactivation of osteoimplants to enhance osseointegration. In this regard, adipose derived stem cells ASCs offer interesting perspectives in implantology because they are fast and easy to isolate.

However, not all materials licensed for bone implants are equally suited for cell adhesion. Surface modifications are under investigation to promote cytocompatibility and cell growth. The presented study focused on influences of a Nitinol -nanoparticle coating on ASCs. Possible toxic effects as well as influences on the osteogenic differentiation potential of ASCs were evaluated by viability assays, scanning electron microscopy, immunofluorescence and alizarin red staining.

It was previously shown that Nitinol -nanoparticles exert no cell toxic effects to ASCs either in soluble form or as surface coating. Here we could demonstrate that a Nitinol -nanoparticle surface coating enhances cell adherence and growth on Nitinol -surfaces. No negative influence on the osteogenic differentiation was observed. Nitinol -nanoparticle coatings offer new possibilities in implantology research regarding bioactivation by autologous ASCs, respectively enhancement of surface attraction to cells.

Physical properties of a new type of self-expandable nitinol stent. To study the new physical properties including hoop strength and flexibility of a newly developed nitinol stent. The new stent was made of a single nitinol wire 0. This was wound around a cylindrical metallic jig with a constant angle to the longitudinal direction, and stents which winding were constructed.

Hoop strength of the stents was measured with a spring gauge and compared with that of Wallstent and Hanaro stents. The flexibility of the new stent was evaluated on the basis of changes in stent diameter when bent in the direction of deg Hoop strength of the new nitinol stent was proportional to 3. A greater number of wires on a lateral cut surface or a greater number of longitudinal windings also resulted in increased strength. However, the former caused an increase in total wire area and the latter resulted increased stent length when compressed.

Hoop strength of the new nitinol stent was superior to that of Wallstent and Hanaro stents, and stent diameter did not decrease when the stent was bent in the direction of degrees. Hoop strength of the new nitinol stent was most significantly affected by wire thickness. The stent was very flexible and thus seemed suitable for an angled lumen.

Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine CH2NH , ammonia NH3 , and hydrogen cyanide HCN. Danger, G. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system.

Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments.

Infrared spectroscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. During the ice warming, this reaction leads to the formation of poly methylene-imine polymers. In a methanimine excess, long polymers are formed. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions.

Passive base isolation with superelastic nitinol SMA helical springs. Seismic isolation of structures such as multi-story buildings, nuclear reactors, bridges, and liquid storage tanks should be designed to preserve structural integrity. By implementing seismic isolation technology, the deformation of superstructures can be dramatically reduced, consequently helping to protect their safety as well.

In this paper, an innovative type of passive base isolation system, which is mainly composed of superelastic nitinol SMA helical springs, is developed. In order to verify the effectiveness of the proposed system, a two-story experimental steel frame model is constructed, and two superelastic SMA helical springs are thermo-mechanically built in the laboratory. To describe the nonlinear mechanical properties of the superelastic SMA helical springs under reciprocating load, a phenomenological model is presented in terms of a series of tensile tests.

Afterwards, a numerical model of the two-story frame with the suggested isolation system is set up to simulate the response of the isolated frame subjected to an earthquake. Both the experimental and the numerical simulation results indicate that the proposed base isolation system can remarkably suppress structural vibrations and has improved isolation effects when compared with a steel spring isolation system.

Due to the capabilities of energy dissipation as well as fully re-centering, it is very applicable to utilize the suggested isolation system in base isolated structures to resist earthquakes. Nitinol stents in the treatment of benign proximal tracheal stenosis or tracheomalacia.

Nitinol stents have been used in the treatment of benign tracheal stenosis. A retrospective review of five patients treated at Stobhill Hospital over the last six and a half years is presented. Age at presentation ranged from 17 to 76 years. The minimum follow-up period was 23 months and the maximum was 78 months. All our patients were successfully decannulated, with none requiring recannulation. Four patients developed granulation tissue related to the stent at intervals ranging from three weeks to 41 months post stenting.

Topical mitomycin C application has been useful after resection of granulations using the carbon dioxide CO2 laser. Stent migration occurred in one patient three weeks after insertion. Nitinol stents are easy to insert and effective in the treatment of tracheal stenosis, but can have associated morbidity. Their use should be considered carefully, as insertion should be regarded as permanent.

Publications reporting experience and outcome with the use of Nitinol stents in the trachea are reviewed. To evaluate the patency and the freedom of target lesion revascularization of the 4-French Pulsar self-expandable SE nitinol stent for the treatment of long femoropopliteal occlusive disease in a two-center, prospective, all-comers registry with a follow-up period of 12 months.

This registry enrolled 36 patients with symptomatic femoropopliteal long lesions for recanalization and implantation of the 4-French Pulsar SE nitinol stent. Routine follow-up examination including duplex ultrasound was performed after 6 and 12 months. Primary patency was defined as no binary restenosis on duplex ultrasound Peak systolic velocitiy ration PSVR Pulsar SE nitinol stent for endovascular intervention of femoropopliteal disease with a mean lesion length of Diabetes and renal insufficiency had no negative impact on the patency rate.

Laser shape setting of superelastic nitinol wires: Functional properties and microstructure. Shape setting is one of the most important steps in the production route of Nitinol Shape Memory Alloys SMAs , as it can fix the functional properties, such as the shape memory effect and the superelasticity SE. In this work, a laser beam was adopted for performing straight shape setting on commercially available austenitic Nitinol thin wires.

The laser beam, at different power levels, was moved along the wire length for inducing the functional performances. Calorimetric, pseudo-elastic and microstructural features of the laser annealed wires were studied through differential scanning calorimetry, tensile testing and high energy X-ray diffraction, respectively.

It can be stated that the laser technology can induce SE in thin Nitinol wires: the wire performances can be modulated in function of the laser power and improved functional properties can be obtained. Simon nitinol vena cava filters: effectiveness and complications. Purpose: The aim of this retrospective analysis was to evaluate the clinical safety and effectiveness of the simon nitinol inferior vena cava filter SNF for prevention of pulmonary embolism. Patients and Methods: patients 63 male, 54 female; aged Patient reports were retrospectively analysed for complications during and after implantation and deep venous thrombosis DVT and pulmonary embolism before and after implantation.

Helical-CT with contrast media and plain abdominal radiography were performed on 35 patients, helical-CT alone on two patients. We checked the position and configuration of the SNF and looked for a perforation of the filter legs through the wall of the inferior vena cava IVC. The IVC and deep pelvic veins were analysed for patency. There was no significant increase in thrombosis of the deep pelvic veins and the IVC after implantation.

Pulmonary re-embolism PE was documented in 9 out of patients 7. One out of the 35 examined patients 2. Dislocation of the SNF more than 10 mm occurred in one out of 35 patients 2. We found no occlusion of the IVC. Laser-assisted fixation of a nitinol stapes prosthesis. Otosclerosis is an inner ear bone disease characterized by fixation of the stapes and consequently progressive hearing loss. One treatment option is the surgical replacement of the stapes by a prosthesis.

When so called "smart materials" like nitinol are used, prosthesis fixation can be performed using a laser without manual crimping on the incus. However, specific laser-prosthesis interactions have not been described yet. Total energy for closure was determined.

Suitable laser parameters pulse duration, power per pulse, distance between tip of the laser fiber and prosthesis were assessed. Specific laser-prosthesis interactions were recorded. Especially the diode laser was found to be an appropriate energy source.

Energy should be transmitted through a laser fiber equipollent to the prosthesis band diameter. Specific deformation characteristics due to the zonal prosthesis composition have to be taken into account. Lasers Surg. A year-old woman presented with a large femoropopliteal aneurysm. A covered nitinol stent was implanted successfully and complete exclusion of the aneurysm was achieved. At follow-up 5 months later the stent was still patent and the patient was free of symptoms.

However, moderate stenosis was seen at the proximal end of the stent. This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents. The research is aimed at addressing two of the primary failure modes in Nitinol endovascular stents: fatigue-crack growth and overload fracture. The small dimensions of stents, coupled with their complex geometries and variability among manufacturers, make it virtually impossible to determine generic material constants associated with specific devices.

Instead, the research utilizes a hybrid of standard test techniques fracture mechanics and x-ray micro-diffraction and custom-designed testing apparatus for the determination of the fracture properties of specimens that are suitable representations of self-expanding Nitinol stents. Specifically, the role of texture crystallographic alignment of atoms and the austenite-to-martensite phase transformation on the propagation of cracks in Nitinol was evaluated under simulated body conditions and over a multitude of stresses and strains.

Statistical characteristics of surface integrity by fiber laser cutting of Nitinol vascular stents. Laser cutting is the dominant process for manufacturing Nitinol stents. Conventional laser cutting usually produces unsatisfactory surface integrity which has a significant detrimental impact on stent performance. Emerging as a competitive process, fiber laser with high beam quality is expected to produce much less thermal damage such as striation, dross, heat affected zone HAZ , and recast layer.

To understand the process capability of fiber laser cutting of Nitinol alloy, a design-of-experiment based laser cutting experiment was performed. The kerf geometry, roughness, topography, microstructure, and hardness were studied to better understand the nature of the HAZ and recast layer in fiber laser cutting. Moreover, effect size analysis was conducted to investigate the relationship between surface integrity and process parameters.

Fu, C. Use of nitinol self-expandable stents in 26 dogs with tracheal collapse. A study was designed to describe a novel approach to the treatment of tracheal collapse TC in dogs using self-expandable nitinol stents. Medical records were reviewed retrospectively for 26 client owned dogs in which nitinol stents were deployed. The entire length of trachea was supported independently of the extent of TC. Two overlapping stents were used instead of one in cases where one stent was not spanning the entire trachea adequately.

The diameter of the cranial radiolucent portion of trachea, just behind the cricoid cartilage, was measured as a specific landmark to select the appropriate size of the stent. Two self-expandable nitinol stents were inserted in 9 of 26 dogs; the trachea in the rest of the cases was supported with only one stent. A follow up tracheoscopy was performed in 10 of 26 cases with recurrent clinical signs.

Secondary tracheal stenosis in these cases was caused by stent fracture, granuloma or excessive stent shortening. Additional stents were placed successfully to expand the stenotic lumen. A support of the entire trachea may decrease risk of nitinol fracture at the end of the implant.

Multiscale electrochemical analysis of the corrosion of titanium and nitinol for implant applications. Izquierdo, J. SECM was operated in feedback and redox competition modes as a function of potential applied to the substrate. The kinetics of the electron transfer rate on both materials was characterized by mathematical modelling of the Z-approach curves monitored under feedback conditions. The rate constant values greatly depended on the characteristics of the passive layers formed over the metals under potentiostatic control.

A more insulating film was found on nitinol when biased at low polarizations, resulting in smaller tip current increments during tip approach to the investigated surface under positive feedback and competition operation modes.

However, at higher anodic polarizations, nitinol passive layers experience breakdown, and therefore tip current values reflect the release of metal cations from the biomaterial surface. Materials and Methods. Eighteen patients underwent PTA of focal atherosclerotic occlusive disease of distal abdominal aorta. Two symptomatic occlusions and 16 stenoses in 10 male and 8 female patients mean age No complications associated with the procedure occurred.

During the Endovascular treatment primary self-expandable nitinol stent placement of focal atherosclerotic lesions of distal abdominal aorta is a safe method with excellent primary technical and clinical success rates and favourable Long term results. In that evaluation, most specimens were exposed for a year.

Nitinol 60 was added to the test program in High-resolution 3D X-ray imaging of intracranial nitinol stents. Snoeren, Rudolph M. To assess an optimized 3D imaging protocol for intracranial nitinol stents in 3D C-arm flat detector imaging.

For this purpose, an image quality simulation and an in vitro study was carried out. Nitinol stents of various brands were placed inside an anthropomorphic head phantom, using iodine contrast. Experiments with objects were preceded by image quality and dose simulations.

We varied X-ray imaging parameters in a commercially interventional X-ray system to set 3D image quality in the contrast-noise-sharpness space. Beam quality was varied to evaluate contrast of the stents while keeping absorbed dose below recommended values.

Two detector formats were used, paired with an appropriate pixel size and X-ray focus size. Zoomed reconstructions were carried out and snapshot images acquired. High contrast spatial resolution was assessed with a CT phantom. We found an optimal protocol for imaging intracranial nitinol stents. Contrast resolution was optimized for nickel-titanium-containing stents. A high spatial resolution larger than 2. We obtained images of stents of various brands and a representative set of images is shown.

Independent of the make, struts can be imaged with virtually continuous strokes. By balancing the modulation transfer of the imaging components and tuning the high-contrast imaging capabilities, we have shown that thin nitinol stent wires can be reconstructed with high contrast-to-noise ratio and good detail, while keeping radiation doses within recommended values.

Experimental results compare well with imaging simulations. Treatment of malignant gastroduodenal obstruction with using a newly designed complex expandable nitinol stent: initial experiences. We wanted to evaluate the usefulness of a new type of a complex expandable nitinol stent that was designed to reduce the stent's propensity to migration during the treatment of malignant gastroduodenal obstructions.

Two types of expandable nitinol stent were constructed by weaving a single thread of 0. Both ends of the covered stent were fabricated by coaxially inserting the covered stent into the tubular uncovered stent and then attaching the two stents together with using nylon monofilament. Clinical improvement was assessed by comparing the food intake capacity before and after the procedure.

The complications were investigated during the follow up period. Stent placement was successful in all the patients. After stent placement, the symptoms improved in all but one patient. Despite the stent migration, the patient was able to resume a soft diet.

Six patients developed recurrent symptoms of obstruction with tumor overgrowth at a mean of days after the procedure; all the patients underwent coaxial placement of an additional stent with good results. One patient showed recurrence of obstruction due to tumor in-growth, and this was treated by placement of a second stent. Two patients with stent placement in the duodenum suffered from jaundice 26 days and 65 days, respectively, after their procedures. Placement of the newly designed complex expandable nitinol stent seems to be effective for the palliative treatment of malignant gastroduodenal obstructions.

The new stent also seems to help overcome the. Management of stent dislodgment in coarctoplasty of aorta with three overlapping self-expandable nitinol stents. We describe a case of native coarctation of aorta managed with three self-expandable nitinol stents. After balloon pre-dilation, the first and second stents were dislodged. The coarcted area was successfully treated with the third stent overlapped with the previous stents.

During follow up 30 months , the patient was free of complications. It seems that implantation of multiple overlapping self-expandable stents in aortic coarctation patients, if needed, is safe and possible. Full Text Available This paper presents nano-impact low cycle fatigue behavior of as-deposited amorphous nitinol TiNi thin film deposited on Si wafer. The nitinol film was 3. Each nano-impact test was conducted for a total of fatigue cycles. Depth sensing approach was adapted to understand the mechanisms of film failure.

Based on the depth-time data and surface observations of films using atomic force microscope, it is concluded that the shape of the indenter test probe is critical in inducing the localized indentation stress and film failure. The measurement technique proposed in this paper can be used to optimize the design of nitinol thin films.

Transcatheter aortic value implantation with self-expandable nitinol valved stent: an experimental study in sheep. Objective: to determine the feasibility and safety of transcatheter aortic valve implantation with domestic self-expandable nitinol valved stent in experimental sheep.

Methods: A fresh pig pericardium was cross-linked with a 0. Ten healthy sheep of Under general anesthesia, the device was delivered through catheter into the native aortic valve of the sheep via the femoral artery or abdominal aorta. The animals were followed up for three months. Results: Six devices were successfully delivered at the desired position in six sheep with no occurrence of complications.

Angiographic and hemodynamic studies confirmed that the stents were fixed at correct position with competent valve function immediately and 90 days after the procedure. Technical failure or fatal complications occurred in the remaining four sheep. Conclusion: Implantation of a domestic nitinol self-expandable stent at the aortic valve position through a transcatheter approach is feasible in experimental sheep.

Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease PAD due to its minimally invasive nature and associated reductions in short-term morbidity and mortality. The mechanical properties of the superelastic Nitinol alloy have played a major role in the explosion of peripheral artery stenting, with modern stents demonstrating reasonable resilience and durability. Yet in the superficial femoral and popliteal arteries, even the newest generation Nitinol stents continue to demonstrate clinical outcomes that leave significant room for improvement.

Restenosis and progression of native arterial disease often lead to recurrence of symptoms and reinterventions that increase morbidity and health care expenditures. One of the main factors thought to be associated with stent failure in the femoropopliteal artery FPA is the unique and highly dynamic mechanical environment of the lower limb. Clinical and experimental data demonstrate that the FPA undergoes significant deformations with limb flexion.

It is hypothesized that the inability of many existing stent designs to conform to these deformations likely plays a role in reconstruction failure, as repetitive movements of the leg and thigh combine with mechanical mismatch between the artery and the stent and result in mechanical damage to both the artery and the stent. In this review we will identify challenges and provide a mechanical perspective of FPA stenting, and then discuss current research directions with promise to provide a better understanding of Nitinol , specific features of stent design, and improved characterization of the biomechanical environment of the FPA to facilitate development of better stents for patients with PAD.

Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties. The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential.

However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life.

Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials. Endovascular stenting has matured into a commonly used treatment for peripheral arterial disease PAD due to its minimally invasive nature and associated reductions in short-termmorbidity and mortality.

We wanted to determine the technical and clinical efficacy of using a PTFE-covered self-expandable nitinol stent for the palliative treatment of malignant biliary obstruction. Thirty-seven patients with common bile duct strictures caused by malignant disease were treated by placing a total of 37 nitinol PTFE stents. These stents were covered with PTFE with the exception of the last 5 mm at each end; the stent had an unconstrained diameter of 10 mm and a total length of 50 80 mm.

The patient survival rate and stent patency rate were calculated by performing Kaplan-Meier survival analysis. The bilirubin, serum amylase and lipase levels before and after stent placement were measured and then compared using a Wilcoxon signed-rank test. The average follow-up duration was Placement was successful in all cases.

There were no immediate complications. Three patients demonstrated stent sludge occlusion that required PTBD percutaneous transhepatic biliary drainage irrigation. Two patients experienced delayed stent migration with stone formation at 7 and 27 weeks of follow-up, respectively. The bilirubin levels were significantly reduced one week after stent insertion p nitinol stent is safe to use with acceptable complication rates. This study is similar to the previous studies with regard to comparing the patency rates and survival rates.

Self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty. The feasibility of self-expanding nitinol stents for treatment of infragenicular arteries following unsuccessful balloon angioplasty was assessed. Options for lower limb percutaneous revascularization are limited, especially for complex vessel obstruction. Until recently, no self-expanding stent for the use in the infragenicular arteries was available.

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