BACKGROUND AND PURPOSE:We report a preclinical study of a second-generation endoluminal device (Pipeline Embolization Device [PED-2] for aneurysmal occlusion and compare the PED-2 with its first-generation predecessor (PED-1).

The reaction behavior and development of network microstructure in the RAFT polymerization of OEGDMA were investigated. The polymerization rate of the RAFT system was much lower than in conventional FRP, largely due to the low propagating‐radical concentration determined by the addition‐fragmentation equilibrium. A mild autoacceleration occurred as the addition reaction became diffusion‐controlled. The slow chain growth in the RAFT allowed sufficient chain relaxation and a uniform distribution of reacting species. The RAFT polymerization of OEGDMA with longer spacers yielded more homogeneous networks with a lower crosslinking density and lower glass transition temperature than the FRP.magnified image

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Shape memory polymer (SMP) foam‐coated coils (FCCs) are new embolic coils coated with porous SMP designed to expand for increased volume filling and enhanced healing after implantation. The purpose of this study was to compare chronic aneurysm healing after treatment with SMP FCCs to bare platinum coil (BPC) controls in the rabbit elastase aneurysm model. BPCs or SMP FCCs were implanted in rabbit elastase‐induced aneurysms for follow‐up at 30 days (n = 10), 90 days (n = 5), and 180 days (n = 12 for BPCs; n = 14 for SMP FCCs). Aneurysm occlusion and histologic healing, including a qualitative healing score, neointima thickness, collagen deposition, and inflammation were compared between the two groups. The mean neointima thickness was significantly greater in groups treated with SMP FCCs for all three time points. Histologic healing scores and collagen deposition quantification suggested that aneurysms treated with SMP FCCs experience more complete healing of the dome by 90 days, but the differences were not statistically significant. More progressive occlusion and recanalization were observed in aneurysms treated with SMP FCCs, but neither difference was statistically significant. Additionally, the SMP foam used in the FCCs was found to degrade faster in the rabbit elastase model than expected based on previous studies in a porcine sidewall aneurysm model. This study suggests that SMP FCCs can promote neointima formation along the aneurysm neck, and may lead to more complete healing of the dome and neck. These findings indicate potential benefits of this device for aneurysm occlusion procedures. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2466–2475, 2019.

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Introduction Robust wall apposition for flow-diverter stents (FDS) may be important for endothelialization. Using a large series of experimental aneurysms treated with the Pipeline Embolization Device (PED), the objectives of this study were to 1) assess interobserver agreement for the evaluation of wall apposition on post-treatment DSA and evaluate its association with aneurysm occlusion and 2) measure the relationship between wall apposition assessed with histology and aneurysm occlusion rate after PED treatment. Material and methods Saccular aneurysms were created in 41 rabbits and treated with PED. DSA was performed just after the deployment of the device and at follow-up. Three investigators independently graded wall apposition on post-treatment DSA as good or poor. One histopathologist blinded to the angiographic results, graded the wall-apposition on histological samples. We examined the correlation between angiographic occlusion and wall apposition with histology and angiography. Results Wall apposition evaluated on histology was strongly associated with saccular aneurysm occlusion. Sensitivity and specificity of wall apposition to predict complete occlusion at follow-up were, respectively, 76.9% and 84.0% with an overall accuracy 81.6%. In this experimental study, DSA was sub-optimal to assess flow diverter apposition with moderate inter-observer agreement and low accuracy. Conclusion Good wall apposition is strongly associated with complete occlusion following flow-diverter therapy. In this study, DSA is suboptimal for assessing wall apposition of FDS. These findings suggest that improved tools for assessing FDS wall apposition are highly relevant.

Purpose to investigate the relationship between hemodynamic conditions created immediately after flow diversion and subsequent occlusion of experimental aneurysms in rabbits. Methods The hemodynamic environment before and after flow diversion treatment of elastase induced aneurysms in 20 rabbits was modeled using image-based computational fluid dynamics. Local aneurysm occlusion was quantified using a voxelization technique on 3D images acquired 8 weeks after treatment. Global and local voxel-by-voxel hemodynamic variables were used to statistically compare aneurysm regions that later thrombosed to regions that remained patent. Results Six aneurysms remained patent at 8 weeks while 14 were completely or nearly completely occluded. Patent aneurysms had statistically larger neck sizes (p=0.0015) and smaller mean transit times (p=0.02). The velocity, vorticity and shear rate were about 2.8 times (p<0.0001) larger in patent regions, i.e. had larger “flow activity”, than regions that progressed to occlusion. Statistical models based on local hemodynamic variables were capable of predicting local occlusion with good precision (84% accuracy), especially away from the neck (92–94%). Predictions near the neck were poorer (73% accuracy). Conclusion These results suggests that the dominant healing mechanism of occlusion within the aneurysm dome are related to slow flow induced thrombosis while near the neck other processes could be at play simultaneously.

Ethylene vinyl acetate (EVA) encapsulation materials have attracted a lot of attention due to their extensive applications in solar cells. Nearly 80% of photovoltaic (PV) modules are encapsulated by EVA materials. EVA has lots of advantages, such as good light transmittance and elasticity, low processing temperature, excellent melt fluidity, and adhesive property. In addition, the price is low, which makes it very suitable as a solar cell encapsulation material. However, there are also some problems with EVA. Its damp-heat aging resistance and ultraviolet aging resistance are not good. It also easily degrades and becomes yellow, reducing the energy conversion efficiency of the solar cell. This article pays special attention to improving the performance of EVA encapsulation films. In addition, it differentiates between different properties, including the aging resistance, adhesive strength and energy conversion efficiency.