nitinol and Necrosis

To solve the problems of small one-time ablation range and easy charring of the tissue around the electrode associated with the tumor radiofrequency ablation needle, based on the multiphysical field coupling analysis software COMSOL, the effects of needle material, the number of sub needles and the bending angle of sub needles on the ablation effect of radiofrequency ablation electrode needle were studied. The results show that compared with titanium alloy and stainless steel, nickel titanium alloy has better radiofrequency energy transmission efficiency and it is the best material for electrode needle. The number of sub needles has a great influence on the average necrosis depth and the maximum necrosis diameter. Under the same conditions, the more the number of sub needles, the larger the volume of coagulation necrosis area. The bending angle of the needle has a great effect on the maximum diameter of the coagulated necrotic area, but has little effect on the average necrotic depth. Under the same other conditions, the coagulation necrosis area formed by ablation increased with the increase of the bending angle of the sub needle. For the three needles with bending angles of 60 °, 90 ° and 120 ° analyzed in this paper, the one with bending angle of 120 ° can obtain the largest coagulation necrosis area. In general, the design of nickel titanium alloy with 120 ° bending 8-pin is the optimal. The average depth of radiofrequency ablation necrosis area is 32.40 mm, and the maximum necrosis diameter is 52.65 mm. The above optimized design parameters can provide guidance for the structure and material design of tumor radiofrequency ablation needle.. 为解决肿瘤射频消融针一次性消融范围小以及电极周围组织易发生烧焦炭化的问题，本文基于多物理场耦合分析软件COMSOL，研究针体材料、子针个数和子针弯曲角度对射频消融电极针消融效果的影响规律。研究结果表明，相较于钛合金和不锈钢，镍钛合金具有更好的射频能量传导效率，是电极针的最佳制作材料；子针个数对平均坏死深度和最大坏死直径均有较大影响，相同条件下，子针个数越多，凝固坏死区域体积越大；子针的弯曲角度对凝固坏死区域的最大直径影响较大，对平均坏死深度的影响较小。在其它条件均相同的情况下，消融形成的凝固坏死区域随子针弯曲角度的增加而增大。对于本文分析的60 °、90 °和120 °三种子针弯曲角度而言，120 °的弯曲角度可获得最大的凝固坏死区域。综合而言，镍钛合金120 °弯曲8子针的设计最优，射频消融坏死区域的平均深度为32.40 mm，最大坏死直径为52.65 mm。上述优化设计参数可为肿瘤射频消融针的结构与材料设计提供指导。.

Topics: Alloys; Catheter Ablation; Humans; Necrosis; Needles; Neoplasms; Temperature

To understand the histologic changes of prostate tissue induced by temporary implantable nitinol device (cTIND) in a canine model.. The cTIND is a small, symmetric device comprised of nitinol wire loops welded together on an axis, which exert radial force on the tissue to induce a targeted ischemic effect. The cTIND was implanted in three live canine models, which were monitored for 14 days post-index procedure. Device placement was monitored via serial fluoroscopy and biologic effects of cTIND were studied via histopathology.. The cTIND was successfully placed in the canine models and remained securely in position until the animal was sacrificed on postoperative day 14. The cTIND treated tissue demonstrated an abrupt transition from normal, viable prostatic glandular tissue to an area of shrunken necrosis and fibrosis between the two.. In the canine models, the cTIND created focal areas of ischemic necrosis resulting in incisions in the peri-urethral prostate with minimal inflammation.

Topics: Alloys; Animals; Dogs; Ischemia; Male; Minimally Invasive Surgical Procedures; Necrosis; Postoperative Complications; Prostate; Prostheses and Implants; Urologic Surgical Procedures, Male

This study sought to compare the local tissue response and subsequent volume of intimal hyperplasia (IH) that develops throughout the maturation of an arteriovenous fistula created using continuous/interrupted polypropylene with that of a novel, metal-alloy, penetrating anastomotic clip device.. Forty-six fistulae were created in 23 sheep under a paired design using the nitinol U-Clip (n = 23) in one hind limb and continuous (n = 20) or interrupted (n = 3) polypropylene suture for the other. Animals were killed at 4 (n = 3), 14 (n = 3), 28 (n = 10), 42 (n = 3), and 180 (n = 4) days. Histological sections were evaluated for quantitative histology and immunohistochemistry.. Compared with continuous polypropylene, U-Clip specimens demonstrated less intima-media area per unit length (IMA/L), proliferating cells, and tissue necrosis at all time points (MANOVA, F = 9.8-24.1, all p ≤ .005; observed power >82%). Specifically, values of IMA/L were reduced by 5% (p = .97), 37% (p = .02), 33% (p < .01), 9% (p = .42), and 14% (p = .22) at the time points of 4, 14, 28, 42, and 180 days respectively. Proliferating cells were reduced by 75% (p < .01), 72% (p = .03), 76% (p = .03), 27% (p = .31), and 60% (p = .01) and tissue necrosis by 67% (p < .01), 58% (p = .02), 40% (p = .33), 21% (p = .43), 77% (p = .11). In a 28-day comparison between U-Clip and interrupted polypropylene the U-Clip group demonstrated a 4% (p = .65) reduction in IMA/L, 74% (p < .01) in proliferating cells and 49% (p < .05) in tissue necrosis.. These results provide evidence of reduced local tissue necrosis, proliferating cells, and IH, favouring arteriovenous fistulae created using the U-Clip anastomotic device over conventional polypropylene suture techniques most evident over the first 4 weeks.

Topics: Alloys; Animals; Arteriovenous Shunt, Surgical; Cell Proliferation; Equipment Design; Femoral Artery; Femoral Vein; Hindlimb; Hyperplasia; Models, Animal; Muscle, Skeletal; Necrosis; Neointima; Polypropylenes; Sheep; Surgical Instruments; Suture Techniques; Sutures; Time Factors

The self-expanding nitinol stent is easy to handle and well tolerated. It offers an improved method in the treatment of perforations of the upper aerodigestive tract. It is easily implantable with rigid and flexible endoscopes. A 45-year-old female patient developed a tracheal necrosis after polytrauma and protracted intubation and ventilation. The permanent cuff pressure caused a 5-cm long fistula located at the posterior trachea 3 cm above the carina. After stabilization of the general condition and spontaneous reduction of the fistula length to 2 cm, we implanted the silicon-covered esophageal stent. Daily bronchoscopic examination was done before and after implantation of the stent. Two days after implantation, we were able to remove the blocked tracheostomy tube. Immediately oral nutrition was possible without complications. Because of its easy and fast application without any complications, the new type of nitinol stent is a promising alternative for ear, nose, and throat patients in bad general condition to provide fast and safe treatment in benign tracheoesophageal fistulas.

Topics: Alloys; Female; Follow-Up Studies; Humans; Intubation, Intratracheal; Middle Aged; Necrosis; Radiography; Stents; Tracheoesophageal Fistula

Our objectives were to quantify the thrombogenicity and extent of vascular injury created by slotted-tube geometry stainless steel and nitinol coronary stents in a rabbit carotid artery model.. Stents were implanted in rabbit right carotid arteries without antiplatelet therapy. Stainless steel stents were implanted for 4 days while nitinol stents were placed for 4 and 14 days (n = 8, 8, and 6, respectively). Stent thrombosis was assessed by thrombus weight, grading thrombus encroachment of the lumen, and by blood flow in the stented and contralateral arteries. Stainless steel stents at 4 days contained more thrombus than 4- and 14-day nitinol stents (20.0 +/- 5.9 versus 2.5 +/- 0.6 and 2.7 +/- 0.3 mg, respectively; P < .000001). Stainless steel stents were more often occluded by thrombus (6 of 8) or contained more subocclusive thrombus (2 of 8) than nitinol stents (0 of 14, P < .002). Resting blood flow was reduced in arteries with stainless steel stents compared with 4- and 14-day nitinol stents (1.5 +/- 2.8 versus 24.0 +/- 2.0 and 25.5 +/- 1.9 mL/min, respectively, P < .000001). Stainless steel stents were less uniformly expanded, had deeper strut penetration into the vascular wall, and were associated with more extensive medial smooth muscle cell necrosis. There were strong correlations (r = .77 to .95) between variables of thrombosis extent (thrombus weight and grade) and histologically determined vascular injury (strut penetration and medial necrosis).. Slotted-tube stainless steel stents were more thrombogenic and created more extensive vascular injury than nitinol stents in a rabbit carotid artery model. The mechanisms underlying these differences probably are related to metallurgic and design geometry properties of the two stent types.

Topics: Acute Disease; Alloys; Animals; Carotid Arteries; Carotid Artery Injuries; Carotid Artery Thrombosis; Equipment Design; Male; Microscopy, Electron, Scanning; Necrosis; Rabbits; Stainless Steel; Stents; Tunica Media; Wounds and Injuries

The purpose of this study was to test the feasibility of implanting and retrieving a heat-activated recoverable temporary stent and to determine its effect on the angiographic, gross and histologic appearance of a normal coronary artery wall.. Permanent coronary stenting is associated with a significant incidence of thrombosis, bleeding and vascular complications. These may be avoided by temporarily stenting for a period of hours to several days.. Seventy-eight stents constructed from the shape-memory nickel-titanium alloy nitinol were deployed by balloon expansion in the coronary arteries of 28 dogs and left in place for up to 6 months. Thirty minutes to 1 week after implantation, 70 stents were recovered by flushing the coronary arteries with 3 to 5 ml of 75 degrees C lactated Ringer solution, with collapse of the stent over a recovery catheter and subsequent withdrawal.. All stents were successfully recovered and removed percutaneously. Mean vessel diameter after stenting was 12 +/- 6% (p < 0.05) greater than baseline diameter. Mean vessel diameter after stent removal remained enlarged (6 +/- 3%, p < 0.05). No angiographic or gross evidence of thrombosis, dissection, embolization, migration or spasm was associated with implantation or recovery. Microscopic examination revealed minor intimal injury in 40 segments (51%). Microscopic focal medial necrosis was associated with mural platelet-fibrin thrombus in 23 stented segments (29%) and media was interrupted in 7 (9%).. This study demonstrates the feasibility of a new method of temporary stenting that uses the thermoelastic properties of nitinol to permit reliable recovery of the stent in normal canine coronary arteries.

Topics: Alloys; Animals; Biopsy; Coronary Angiography; Coronary Thrombosis; Coronary Vessels; Dogs; Equipment Design; Feasibility Studies; Hot Temperature; Incidence; Materials Testing; Necrosis; Stents; Thermodynamics; Time Factors; Wounds and Injuries