The Supera Interwoven Nitinol Stent as a Flow Diverting Device in Popliteal Aneurysms

PURPOSE: The feasibility of using a compressed interwoven Supera stent as a flow diverting device for popliteal aneurysms was recently demonstrated in patients. It is unclear, however, what the optimal flow diverting strategy is, because of the fusiform shape of popliteal aneurysms and their exposure to triphasic flow. To assess this flow diverting strategy for popliteal aneurysms, flow profiles and thrombus formation likelihood were investigated in popliteal aneurysm models. MATERIALS AND METHODS: Six popliteal aneurysm models were created and integrated into a pulsatile flow set-up. These models covered a bent and a straight anatomy in three configurations: control, single-lined and dual-lined Supera stents. Two-dimensional flow velocities were visualized by laser particle image velocimetry. In addition, the efficacy of the stent configurations for promoting aneurysm thrombosis was assessed by simulations of residence time and platelet activation. RESULTS: On average for the two anatomies, the Supera stent led to a twofold reduction of velocities in the aneurysm for single-lined stents, and a fourfold reduction for dual-lined stents. Forward flow was optimally diverted, whereas backward flow was generally deflected into the aneurysm. The dual-lined configuration led to residence times of 15–20 s, compared to 5–15 s for the single stent configurations. Platelet activation potential was not increased by the flow diverting stents. CONCLUSION: A compressed Supera stent was successfully able to divert flow in a popliteal aneurysm phantom. A dual-lined configuration demonstrated superior hemodynamic characteristics compared to its single-lined counterpart. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00270-022-03118-x

Optical properties and resonant cavity modes in axial InGaN/GaN nanotube microcavities

Microcavities based on group-III nitride material offer a notable platform for the investigation of light-matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Disk or tube geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whispering gallery modes (WGMs) and small modal volumes. In this article we present the fabrication of homogenous and dense arrays of axial InGaN/GaN nanotubes via a combination of displacement Talbot lithography (DTL) for patterning and inductively coupled plasma top-down dry-etching. Optical characterization highlights the homogeneous emission from nanotube structures. Power-dependent continuous excitation reveals a non-uniform light distribution within a single nanotube, with vertical confinement between the bottom and top facets, and radial confinement within the active region. Finite-difference time-domain simulations, taking into account the particular shape of the outer diameter, indicate that the cavity mode of a single nanotube has a mixed WGM-vertical Fabry-Perot mode (FPM) nature. Additional simulations demonstrate that the improvement of the shape symmetry and dimensions primarily influence the Q-factor of the WGMs whereas the position of the active region impacts the coupling efficiency with one or a family of vertical FPMs. These results show that regular arrays of axial InGaN/GaN nanotubes can be achieved via a low-cost, fast and large-scale process based on DTL and top-down etching. These techniques open a new perspective for cost effective fabrication of nano-LED and nano-laser structures along with bio-chemical sensing applications

Extraction of plasticity parameters of GaN with high temperature, in situ micro-compression

Micro-pillar compression has been utilised in a novel elevated temperature technique, in situ in the SEM to characterise the plasticity of gallium nitride (GaN) {0001}-oriented euhedral prisms grown by metallorganic vapor phase epitaxy. Electron backscatter diffraction was used to confirm the orientation of the prisms, and deformation was observed to occur via 2nd order pyramidal slip on the (11 (2) over bar2)(11 (2) over bar3) slip system. Analysis of the micro-compression data allowed extraction of fundamental deformation parameters of GaN from 24.5 to 479.3 degrees C. The strain rate sensitivity parameter was determined to be 0.0234 +/- 0.0073 both by constant strain rate micro-compressions and micro-compression strain rate jump tests. The measured activation volume was 3.88 +/- 0.13 x 10(-29) m(3), and the activation energy was 0.9 +/- 0.2 eV. (c) 2012 Elsevier Ltd. All rights reserved

Secondary procedures after aortic aneurysm repair with fenestrated and branched endografts

Purpose: To investigate the secondary procedures in patients with previous endovascular aortic repair by fenestrated or branched stent-grafts for aneurysms involving the renal and visceral vessels. Methods: Between January 2001 and May 2010, 107 consecutive high-risk patients (97 men; mean age 73 years, range 50-86) with aortic aneurysms involving the renal and visceral arteries were treated with endovascular techniques. A custom-made Zenith graft was used in all patients. All secondary graft-related procedures performed in the perioperative period and during follow-up were analyzed. Estimates of survival, freedom from migration/type I endoleak, and freedom from any device-related secondary procedures were assessed with Kaplan-Meier analyses. Results: The 30-day mortality rate was 1.9%. During follow-up (mean 25 months, range 1-94), 34 secondary procedures were performed in 28 (26.2%) patients for 6 (17.6%) limb graft stenoses/thromboses (5.6% of 107 cases), 8 (23.5%) in-stent visceral vessel stenoses/occlusions (7.5% of 107 cases), 8 (23.5%) migrations/type I endoleaks with/without visceral stent fractures (7.5% of 107 cases), and 12 (35.3%) type III endoleaks (9.3% of 107 cases). The mean interval between the primary and secondary procedures was 12.9 months (range 1-68). In 26 (76.5%) of 34 cases, a secondary endovascular procedure was performed; in the remaining 8 (23.5%) cases, the complication was treated surgically. The secondary procedure was unsuccessful in 9 cases of visceral vessel compromise (failure to cannulation, stent fracture/migration, in-stent stenosis/occlusion). Estimated 3-year survival was 77%, while the 3-year rate for freedom from any device-related secondary procedure was 75.5%. Conclusion: The incidence of early and late complications requiring a secondary procedure after treatment with fenestrated or branched devices was not negligible. Endoleak type III represented the most common cause for reintervention during follow-up. Secondary procedures performed for visceral vessel compromise had high rates of treatment failure. Accurate preoperative planning, the advent of new materials/ techniques, and strict followup could be the key factors to improving the results of fenestrated or branched stent-graft interventions and to reduce the rate of secondary procedures. © 2011 by the International Society of Endovascular Specialists

Endovascular Aortic Aneurysm Repair with the Endurant Stent-graft: Early and 1-year Results from a European Multicenter Experience

Purpose: To assess preliminary results of the Endurant stent-graft, which was developed to treat patients with abdominal aortic aneurysms (AAAs) and challenging aortoiliac anatomy. Materials and Methods: From November 2007 to October 2008, 45 patients with AAAs were treated with the Endurant stent-graft in three European vascular centers. Thirty-eight of the 45 patients (84%) had a hostile anatomy of the proximal neck. Early (30 days), early midterm (6 months), and late midterm (1 year) results were analyzed in terms of technical success, clinical success, morbidity, and mortality. Results: Intraoperative immediate technical and clinical success was achieved in all cases. At completion angiography, a type II endoleak was detected in seven of the 45 patients (16%) and an iliac limb stenosis was diagnosed and successfully treated in five (11%). At discharge, computed tomography demonstrated a type I endoleak in one of the 45 patients (2.2%). At 30 days, a graft limb thrombosis was diagnosed (2.2%) and successfully treated. The 30-day overall technical and clinical success rates were 97.8% (44/45 cases) and 95.6% (43/45 cases), respectively. During follow-up (mean duration, 8 months; range, 5-16 months), the type I endoleak was successfully treated with an aortic extension. Estimated freedom from type I or III endoleak and repeat intervention at 1 year was 97.8% (44/45 cases) and 93.3% (42/45 cases), respectively. Conclusions: The initial experience shows that the Endurant stent-graft appears to be effective in endovascular repair of AAAs in patients with hostile aortoiliac anatomy. This graft permits a broader group of patients to be treated with endovascular aneurysm repair; however, further studies are needed to evaluate the long-term results. © 2010 SIR