Background Multiple studies and meta-analyses have described the technical and clinical outcomes in large cohorts of aneurysm patients treated with flow diverters (FDs). Variations in evaluation methodology complicate making comparisons among studies, hinder understanding of the device behavior, and pose an obstacle in the assessment of further advances in FD therapy. Methods A multidisciplinary panel of neurointerventionalists, imaging experts, and neuroradiologists convened with the goal of establishing consensus recommendations for the standardization of image analyses in FD studies. Results A standardized methodology is proposed for evaluating and reporting radiological outcomes of FD treatment of intracranial aneurysms. The recommendations include general imaging considerations for clinical studies and evaluations of longitudinal changes, such as neointimal lining and stenosis. They cover standards for classification of aneurysm location, morphology, measurements, as well as the assessment of aneurysm occlusion, wall apposition, and neck coverage. These reporting standards further define four specific braid deformation patterns: foreshortening, fish-mouthing, braid bump deformation, and braid collapse, collectively termed ‘F2B2’. Conclusions When widely applied, standardization of methods of measuring and reporting outcomes will help to harmonize the assessment of treatment outcomes in clinical studies, help facilitate communication of results among specialists, and help enable research and development to focus on specific aspects of FD techniques and technology.

Intracranial atherosclerotic disease (ICAD) involves the build-up of atherosclerotic plaques in cerebral arteries, significantly contributing to stroke worldwide. Diagnosing ICAD entails various techniques that measure arterial stenosis severity. Digital subtraction angiography, CT angiography, and magnetic resonance angiography are established methods for assessing stenosis. High-resolution MRI offers additional insights into plaque morphology including plaque burden, hemorrhage, remodeling, and contrast enhancement. These metrics and plaque traits help identify symptomatic plaques. Techniques like transcranial Doppler, CT perfusion, computational fluid dynamics, and quantitative MRA analyze blood flow restrictions due to ICAD. Intravascular ultrasound or optical coherence tomography have a very high spatial resolution and can assess the structure of the arterial wall and the plaque from the lumen of the target vascular territory. Positron emission tomography could further detect inflammation markers. This review aims to provide a comprehensive overview of the spectrum of current modalities for atherosclerotic plaque analysis and risk stratification.

Background Flow diversion has become a standard treatment for cerebral aneurysms. However, major drawbacks include the need for dual antiplatelet therapy after implant and delayed complete occlusion of the aneurysm, which occurs when new tissue growth excludes the aneurysm from the parent artery. Biomimetic surface modifications such as the phosphorylcholine polymer (Shield surface modification) represent major advances in reducing thrombogenicity of these devices. However, in vitro studies have raised concerns that this modification may also delay endothelialization of flow diverters. Methods Bare metal Pipeline, Pipeline Shield, and Vantage with Shield devices were implanted in the common carotid arteries (CCAs) of 10 rabbits (two in the left CCA, one in the right CCA). Following implant and at 5, 10, 15, and 30 days, the devices were imaged with high-frequency optical coherence tomography and conventional angiography to evaluate tissue growth. At 30 days the devices were explanted and their endothelial growth was assessed with scanning electron microscopy (SEM) at five locations along their length using a semi-quantitative score. Results The average tissue growth thickness (ATGT) was not different between the three devices. Neointima was apparent at 5 days and all devices demonstrated similar ATGT at each time point. On SEM, no difference was found in the endothelium scores between the device types. Conclusion In vivo, neither the Shield surface modification nor the device design (Vantage) altered the longitudinal healing of the flow diverter.

Background: Flow diverters carry the risk of thromboembolic complications (TEC). We tested a coating with covalently bound heparin that activates antithrombin to address TEC by locally downregulating the coagulation cascade. We hypothesized that the neuroimaging evidence of TEC would be reduced by the coating.Methods: 16 dogs were implanted with overlapping flow diverters in the basilar artery, separated into two groups: heparin-coated (n=9) and uncoated (n=7). Following implantation, high-frequency optical coherence tomography (HF-OCT) was acquired to quantify acute thrombus (AT) formation on the flow diverters. MRI was performed postoperatively and repeated at 1, 2, 3, 4, and 8 weeks, consisting of T1-weighted imaging, time-0f-flight (ToF), diffusion weighted imaging (DWI), susceptibility weighted imaging (SWI), and fluid attenuated inversion recovery (FLAIR) sequences. Neurological examinations were performed throughout the 8-week duration of the study.Results: The mean AT volume on coated devices was lower than uncoated (0.014 vs 0.018 mm³); however, this was not significant (P=0.3). The mean number of foci of magnetic susceptibility artifacts (MSAs) on SWI was significantly different between the uncoated and coated groups at the 1-week follow-up (P<0.02), and remained statistically different throughout the duration of the study. The AT volume showed a direct linear correlation with the MSA count and 80% of the variance in the MSA could be explained by the AT volume (P<0.001). Pathological analysis showed evidence of ischemic injury at locations of MSA.Conclusions: Heparin-coated flow diverters significantly reduced the number of new MSAs after 1 week follow-up, showing the potential to reduce TEC.

Background The first-pass complete recanalization by mechanical thrombectomy (MT) for the treatment of stroke remains limited due to the poor integration of the clot within current devices. Aspiration can help retrieval of the main clot but fails to prevent secondary embolism in the distal arterial territory. The dense meshes of extracellular DNA, recently described in stroke-related clots, might serve as an anchoring platform for MT devices. We aimed to evaluate the potential of a DNA-reacting surface to aid the retention of both the main clot and small fragments within the thrombectomy device to improve the potential of MT procedures. Methods Device-suitable alloy samples were coated with 15 different compounds and put in contact with extracellular DNA or with human peripheral whole blood, to compare their binding to DNA versus blood elements in vitro. Clinical-grade MT devices were coated with two selected compounds and evaluated in functional bench tests to study clot retrieval efficacy and quantify distal emboli using an M1 occlusion model. Results Binding properties of samples coated with all compounds were increased for DNA (≈3-fold) and decreased (≈5-fold) for blood elements, as compared with the bare alloy samples in vitro. Functional testing showed that surface modification with DNA-binding compounds improved clot retrieval and significantly reduced distal emboli during experimental MT of large vessel occlusion in a three-dimensional model. Conclusion Our results suggest that clot retrieval devices coated with DNA-binding compounds can considerably improve the outcome of the MT procedures in stroke patients.

Background Intrasaccular flow-disrupting devices are a safe and effective treatment strategy for intracranial aneurysms. We utilized high-frequency optical coherence tomography (HF-OCT) and digital subtraction angiography (DSA) to evaluate SEAL Arc, a new intrasaccular device, and compare the findings with the well-established Woven EndoBridge (WEB) device in an animal model of saccular aneurysms. Methods In a rabbit model, elastase-induced aneurysms were treated with SEAL Arc (n=11) devices. HF-OCT and DSA were performed after implant and repeated after 12 weeks. Device protrusion and malapposition were assessed at implant time and scored on a binary system. Aneurysm occlusion was assessed at 12 weeks with the WEB Occlusion Scale and dichotomized to complete (A and B) or incomplete (C and D) occlusion. The percentage of neointimal coverage after 12 weeks was quantified using HF-OCT. We compared these data to previously published historical controls treated with the gold-standard WEB device (n=24) in the same model. Results Aneurysm size and device placement were not significantly different between the two groups. Complete occlusion was demonstrated in 80% of the SEAL Arc devices, which compared favorably to the 21% of the aneurysms treated with WEB devices (P=0.002). Neointimal coverage across SEAL Arc devices was 86±15% compared with 49±27% for WEB (P=0.001). Protruding devices had significantly less neointimal coverage (P<0.001) as did incompletely occluded aneurysms (P<0.001). Histologically, all aneurysms treated with SEAL Arc devices were completely healed. Conclusion Complete early aneurysm occlusion was frequently observed in the SEAL Arc treated aneurysms, with significant neointimal coverage after 12 weeks.