Grading of Regional Apposition after Flow-Diverter Treatment (GRAFT): a comparative evaluation of VasoCT and intravascular OCT

Three-dimensional fusion imaging to assess apposition of low-profile visualized intraluminal support stent for intracranial aneurysm coiling

Objective

To investigate on three-dimensional (3D) fusion images the apposition of low-profile visualized intraluminal support (LVIS) stents in intracranial aneurysms after treatment and assess inter-rater reliability.

Materials and methods

Records of all patients with unruptured intracranial aneurysms who were treated with the LVIS stent were retrospectively accessed and included in this study. Two neurosurgeons evaluated the presence of malapposition between the vessel walls and the stent trunk (crescent sign) and the vessel wall and the stent edges (edge malappostion) on 3D fusion images. These images were high-resolution cone-beam computed tomography images of the LVIS stent fused with 3D-digital subtraction angiography images of the vessels. Associations between malapposition and aneurysm location were assessed by Fisher's exact test, and inter-rater agreement was estimated using Cohen's kappa statistic.

Results

Forty consecutive patients were included. In all patients, 3D fusion imaging successfully visualized the tantalum helical strands and the closed-cell structure of the nitinol material of the low-profile visualized intraluminal support. A crescent sign was observed in 27.5 % and edge malapposition in 47.5 % of the patients. Malapposition was not significantly associated with location (p = 0.23 crescent sign, p = 0.07 edge malapposition). Almost perfect (κ = 0.88) and substantial (κ = 0.76) agreements between the two raters were found for the detection of crescent signs and edge appositions, respectively.

Conclusions

3D fusion imaging provided clear visualization of the LVIS stent and parent arteries, and could detect malapposition with excellent inter-rater reliability. This technique may provide valuable guidance for surgeons in determining postoperative management.

Diluted contrast media combined with high-resolution C-arm CT for evaluating apposition of flow diversions in a porcine model

BACKGROUND

In intracranial stenting, good stent apposition is crucial, and high-resolution C-arm computer tomography (CT) is utilized to assess whether stent apposition is complete. This study was aimed at finding optimal hypertonic or isotonic contrast media injection concentration for high-resolution C-arm CT to assess apposition of flow diversion (FD) after carotid artery stenting in swine.

METHODS

Twelve FD stents were implanted into the left carotid artery of Bama swine through the endovascular method. During high-resolution C-arm CT scanning, 6%, 8%, 10%, 12%, and 14% dilution percentages of hypertonic contrast media (iopromide 370 mg/ml) and 10%, 12%, 14%, 16%, and 18% dilution percentages of isotonic contrast media (iodixanol 320 mg/ml) were separately injected. A radiologist and a neuro-interventional specialist evaluated and qualitatively scored the post-processed images, and intravascular ultrasound (IVUS) was used to verify the accuracy of these images.

RESULTS

Overall, 12 FD stents were implanted into the left common carotid artery of 12 swine, with a technical success rate of 100%. The best reconstructed images used to observe stent apposition were achieved with iopromide diluted to a concentration of 12% (all P < .05) or iodixanol diluted to a concentration of 16% (all P < .05). Malapposition was noted in one case, and good apposition was noted in 11 cases. These results were consistent with IVUS observations.

CONCLUSION

Injecting iopromide or iodixanol diluted to 12% or 16% during high-resolution C-arm CT scanning, respectively, can help evaluate FD stent apposition and obtain optimal image quality.

High-frequency optical coherence tomography for endovascular management of cerebral aneurysms

Endovascular management of intracranial aneurysms has become the mainstay of treatment in recent years; however, retreatment rates remain as high as 1 in 5. High-frequency optical coherence tomography (HF-OCT) is an emerging imaging modality for the assessment, treatment and follow-up of cerebral aneurysms. EMBASE and SCOPUS databases were searched for studies relating to the management of intracranial aneurysm with OCT. A combination of keywords were used including 'cerebral aneurysm', 'intracranial aneurysm', 'high-frequency optical coherence tomography', 'optical coherence tomography', and 'optical frequency domain imaging'. There were 23 papers included in this review. For the assessment of intracranial aneurysm, OCT was able to accurately assess aneurysm morphology as well as detailed analysis of arterial wall layers. During IA treatment, OCT was used to assess and troubleshoot stent placement to optimise successful isolation from the circulation. In the follow-up period, endothelial growth patterns were visualised by OCT imaging. OCT shows promise for the treatment of IAs at all stages of management. Due to the novel development of HF-OCT, there is limited longitudinal data in human studies. Further research in this area is required with a focus specifically on long-term treatment outcomes in humans.

Longitudinal healing flow diverting stents with phosphorylcholine surface modification

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.

Aneurysm Treatment With the Pipeline Vantage Embolization Device in Retrospective Evaluation: Periprocedural Results from the Pipe-VADER Study

OBJECTIVE

The Pipeline Vantage Embolization Device is a fourth-generation flow diverter with an antithrombotic coating and a reduced profile compared to previous Pipeline versions. The objective of this study was to evaluate the procedural feasibility, safety, and efficacy of this device.

METHODS

The Pipe-VADER study was designed as a retrospective, observational study of consecutive patients treated with the Vantage at 3 neurovascular centers. Patient and aneurysm characteristics, procedural parameters, early complications, and extent of postinterventional contrast retention were analyzed on an intention-to-treat basis.

RESULTS

Twenty-eight patients with 31 aneurysms (median size: 5.0 mm, posterior circulation: 4 [12.9%], ruptured: 5 [16.1%]) were included. The technical success rate was 100%, with multiple stents used in 4/30 (13.3%) procedures. Of the 30 procedures, adjunctive coiling was performed in 3 (10.0%) and balloon angioplasty in 2 (6.7%). Median procedure time was 62 minutes. Procedural ischemic stroke occured in 4 (13.3%) cases, whereof 2 were major strokes (6.6%). There were no hemorrhagic complications. Initial contrast retention was observed in 29/31 (93.5%) aneurysms. All 27 overstented side vessels were patent at the end of the procedure. Short-term follow-up (median: 5 months) showed complete and favorable occlusion rates of 70% (14/20) and 80% (16/20), respectively.

CONCLUSIONS

The new Pipeline Vantage appears to be safe and feasible for the treatment of intracranial aneurysms and warrants further evaluation.

Silk + flow-diverter stent for the treatment of intracranial aneurysms associated with balloon angioplasty: A retrospective study

Background

The silk + flow-diverter stent is increasingly used to treat complex intracranial aneurysms including wide-neck and fusiform aneurysms. Balloon angioplasty has been used to better appose the flow diverter (FD) to the vessel wall and, thus, improve aneurysm occlusion rates and decrease periprocedural complications. Sparse data are available concerning the results of this technique. We report our experience with silk + FD associated with balloon angioplasty for the treatment of intracranial aneurysms.

Methods

A retrospective study was conducted on all patients treated by the silk + FD. Clinical charts, procedural data, and angiographic results were reviewed and compared between those treated with balloon angioplasty. A multivariate analysis was conducted to identify predictors of complications, occlusion, and outcome.

Results

Between July 2014 and May 2016, we identified 209 patients with 223 intracranial aneurysms. There were 176 (84.2%) women and 33 (15.8%) men. The most common stent size used was 4.5 mm in 101 patients (46.1%), followed by 4 mm in 57 patients (26%). Univariate analysis observed that stent diameter was significantly related to aneurysm occlusion (P < 0.05). Patients with more than 1 aneurysm treated with silk + stent have a 9.07 times greater chance of having complications in the procedure than patients with only 01 aneurysm (OR = 9.07; P = 0.0008). Patients who had angioplasty without the use of a balloon have a 13.69-times-higher risk of complications (OR = 13.69; P = 0.0003). Older age, larger aneurysms, and the use of more than 1 FD device were predictors of recanalization.

Conclusion

Endovascular treatment of intracranial aneurysms with the silk + FD associated with balloon angioplasty is a safe and effective therapeutic option. Balloon angioplasty in combination with FD lowers the risk of complications. Higher complication rates and worse outcomes are associated with older age and large aneurysms.

Optical Coherence Tomography in Cerebrovascular Disease: Open up New Horizons

Optical coherence tomography (OCT), based on the backscattering or reflection of near-infrared light, enables an ultra-high resolution of up to 10 μm. The successful application of OCT in coronary artery diseases has sparked increasing interest in its implementation in cerebrovascular diseases. OCT has shown promising potential in the atherosclerotic plaque structure characterization, plaque rupture risk stratification, pre-stenting and post-stenting evaluation, and long-term follow-up in extracranial and intracranial atherosclerotic stenosis (ICAS). In hemorrhagic cerebrovascular diseases, OCT plays an important role in the structure evaluation, rupture risk stratification, and healing and occlusion evaluation following initial treatment in intracranial aneurysms (IAs). In this study, we summarized the applications of OCT in the diagnosis, treatment, and follow-up of cerebrovascular diseases, especially in ICAS and IAs. The current limitations and future directions of OCT in the endovascular treatment of cerebrovascular diseases were also discussed.

Effect of Stent Porosity, Platelet Function Test Usage, and Dual Antiplatelet Therapy Duration on Clinical and Radiographic Outcomes After Stenting for Cerebral Aneurysms: A Meta-Analysis

BACKGROUND

The use of stents with various porosities for treating cerebral aneurysms requires dual antiplatelet therapy (DAPT) without clear guidelines on the utility of platelet function tests (PFTs) and the duration of DAPT. We sought to determine the effects of stent porosity, PFT usage, and DAPT duration on the radiographic and clinical outcomes after stenting of cerebral aneurysms.

METHODS

PubMed was searched on March 29, 2021 for studies of cerebral aneurysm stenting that had specified the stent type and DAPT duration. A random effects meta-analysis was used to measure the prevalence of nonprocedural thrombotic and hemorrhagic events, clinical outcomes, aneurysm occlusion, and in-stent stenosis stratified by stent porosity, PFT usage, and DAPT duration.

RESULTS

The review yielded 105 studies (89 retrospective and 16 prospective) with 117 stenting cohorts (50 high porosity, 17 intermediate porosity, and 50 low porosity). In the high-, intermediate-, and low-porosity stenting cohorts, PFT usage was 26.0%, 47.1%, and 62.0% and the mean DAPT duration was 3.51 ± 2.33, 3.97 ± 1.92, and 5.18 ± 2.27 months, respectively. The intermediate-porosity stents showed a reduced incidence of hemorrhagic events (π = 0.32%) compared with low-porosity stents (π = 1.36%; P = 0.01) and improved aneurysm occlusion (π = 6.18%) compared with high-porosity stents (π = 14.42%; P = 0.001) and low-porosity stents (π = 11.71%; P = 0.04). The prevalence of in-stent stenosis was lower for the intermediate-porosity (π = 0.57%) and high-porosity (π = 1.51%) stents than for the low-porosity stents (π = 3.30%; P < 0.05). PFT use had resulted in fewer poor clinical outcomes (π = 3.54%) compared with those without PFT use (π = 5.94%; P = 0.04). The DAPT duration had no effect on the outcomes.

CONCLUSIONS

In the present meta-analysis, which had selected for studies of cerebral aneurysm stenting that had reported the DAPT duration, intermediate-porosity stents and PFT use had resulted significantly improved outcomes. No effect of DAPT duration could be detected.

Clinical impact of Sim & Size® simulation software in the treatment of patients with cerebral aneurysms with flow-diverter Pipeline stents

OBJECTIVES

This study evaluated the clinical impact of the Sim&Size® simulation software on the endovascular treatment with flow-diverter stents of patients with unruptured saccular intracranial aneurysms.

METHODS

This monocentric retrospective study evaluated a cohort of patients treated with flow-divert stents between June 1, 2014, and December 31, 2019, for cerebral aneurysms. Patients belonged to two groups, patients treated with and without the Sim&Size® simulation software. Univariate, bivariate, and multivariate analyses were used to evaluate the clinical impact of simulation software.

RESULTS

Out of the 73 interventions involving 68 patients analyzed by the study, 76.7% were simulated using the Sim&Size® simulation software, and 23.3% were not. Patients treated with the simulation software had shorter stent lengths (16.00 mm vs. 20.00 mm p-value = 0.001) and surgical time (100.00 min vs. 118.00 min p-value = 0.496). Also, fewer of them required more than one stent (3.6% vs. 17.6% p-value = 0.079). Three patients belonging to the non-stimulated group presented hemorrhagic complications.

CONCLUSIONS

Using the Sim&Size® simulation software for the endovascular treatment of intracranial aneurysms with pipeline flow-diverter stents reduces the stent length.

Evaluation of the apposition in unruptured aneurysms treated with flow diverters by optical coherence tomography: Preliminary clinical experience

Background

The risk of perioperative stroke and the rate of occlusion of long-term aneurysms in the treatment of unruptured aneurysms with flow diverters (FDs) are affected by stent apposition. Optical coherence tomography (OCT) may be an optional technique in evaluating apposition.

Purpose

To explore the feasibility of the OCT imaging technique in evaluating stent apposition in the clinical application of the FD for unruptured aneurysms.

Methods

OCT and Vaso CT were used in patients with indications for surgery to treat unruptured aneurysms with the FDs, to evaluate the apposition of the FDs after fully released, and to analyze OCT images for FDs apposition and compare with corresponding Vaso CT images.

Results

A total of four patients were enrolled, and OCT found malapposition after FDs placement in all four patients, and the maximum gap between the stent and vascular wall ranged from 0.68 to 1.95 mm and the length of malapposition ranged from 1.80 to 7.40 mm. However, Vaso CT found malapposition only in two of the four patients and missed malapposition near aneurysm in all three patients treated by the FD combined with coiling and could not accurately evaluate the maximum gap and the length of the malapposition.

Conclusion

The optical coherence tomography technique is a possible approach to evaluate apposition after the treatment of unruptured aneurysms by the FDs.

The Future of Endovascular Therapy

PURPOSE OF THE REVIEW

This article summarizes a broad range of the most recent advances and future directions in stroke diagnostics, endovascular robotics, and neuromodulation.

RECENT FINDINGS

In the past 5 years, the field of interventional neurology has seen major technological advances for the diagnosis and treatment of cerebrovascular diseases. Several new technologies became available to aid in complex prehospital stroke triage, stroke diagnosis, and interpretation of radiologic findings. Robotics and neuromodulation promise to expand access to established treatments and broaden neuroendovascular indications.

SUMMARY

Mobile applications offer a solution to simplify prehospital diagnostic and transfer decisions. Several prehospital devices are also under development to improve the accuracy of detection of large vessel occlusion (LVO). Artificial intelligence is now routinely used in early diagnosis of LVO and for detecting salvageability of the affected brain parenchyma. Technological advances have also paved the way to incorporate endovascular robotics and neuromodulation into practice. This may expand the deliverability of established treatments and facilitate the development of cutting-edge treatments for other complex neurologic diseases.

Incomplete stent expansion in flow-diversion treatment affects aneurysmal haemodynamics: a quantitative comparison of treatments affected by different severities of malapposition occurring in different segments of the parent artery

Incomplete stent expansion (IncSE) is occasionally seen in flow-diversion (FD) treatment of intracranial aneurysms; however, its haemodynamic consequences remain inconclusive. Through a parametric study, we quantify the aneurysmal haemodynamics subject to different severities of IncSE occurring in different portions of the stent. Two patient cases with IncSE confirmed in vivo were studied. To investigate a wider variety of IncSE scenarios, we modelled IncSE at two severity levels respectively located in the proximal, central, or distal segment of a stent, yielding a total of 14 treatment scenarios (including the ideal deployment). We examined stent wire configurations in 14 scenarios and resolved aneurysm haemodynamics through computational fluid dynamics (CFD). A considerable degradation of aneurysm flow-reduction performance was observed when central or distal IncSE occurred, with the maximal elevations of the inflow rate (IR) and energy loss (EL) being 10% and 15%. The underlying mechanism might be the increased resistance for flow to remain within the FD stent, which forces more blood to leak into the aneurysm sac. Counter-intuitively, a slight reduction of aneurysm inflow was associated with proximal IncSE, with the maximal further reduction of the IR and EL being 5% and 8%. This may be due to the disruption of the predominant parent-artery flow by the collapsed wires, which decreased the strength and altered the direction of aneurysmal inflow. The effects of IncSE vary greatly with the location of occurrence, revealing the importance of performing individualised, patient-specific risk assessment before treatment.

Flow Diverter Apposition in Patients with Large or Giant Intracranial Aneurysms Evaluated on Three-Dimensional Fusion Images Acquired by High-Resolution Cone-Beam Computed Tomography and Digital Subtraction Angiography

OBJECTIVE

To investigate flow diverter (FD) apposition on fused images acquired by high-resolution cone-beam computed tomography (CBCT) and 3-dimensional (3D) digital subtraction angiography.

METHODS

Patients with large or giant internal carotid artery aneurysms treated with Pipeline FDs who underwent CBCT imaging at our institution between October 2016 and May 2019 were included. Two neurosurgeons measured the maximum malapposition between FDs and vessel walls on 3D fusion images of high-resolution CBCT images displaying the FD and 3D digital subtraction angiography images displaying the vessels. Associations between the relative malapposition, FD diameter, vessel diameter, proximal and distal vessel diameter discrepancy, and siphon angle were evaluated by linear regression analysis. Inter-rater and intermethod (3D and 2D image) agreements of the malapposition measurements were assessed by Bland-Altman analysis and by interclass correlation coefficients.

RESULTS

Images of 2 patients were excluded because of image artifacts or fusion errors, and 3D fusion images were acquired in the remaining 26 patients. Our results did not suggest that relative malapposition was associated with vessel diameter (P = 0.12), vessel diameter discrepancy (P = 0.60), or syphon angle (P = 0.34), but relative malapposition increased by an estimated 13% (95% confidence interval: 4%-23%, P = 0.006) for each 1 mm increase in FD diameter. Inter-rater and intermethod agreements for apposition measurements were excellent and good, respectively.

CONCLUSIONS

Three-dimensional fusion images provided clear visualization of structures of both the stent and parent artery with excellent diagnostic reliability. Careful deployment may be needed for FDs with larger diameters, as they tended to have larger relative malapposition.

Failure of Flow Diverter Therapy: Predictors and Management Strategies

Flow diversion is a safe and effective treatment for many types of brain aneurysms. Even so, there remain some aneurysms that persist despite initial treatment. In studies with the longest follow-up (5 yr), at least 5% of aneurysms persist with this treatment modality. As the cumulative experience and clinical indications for flow diversion continue to expand, the anatomic and functional characteristics that are associated with aneurysm persistence are increasingly described. Identification of these factors preoperatively can help to guide initial treatment decisions, enhance monitoring protocols in the follow-up period, and establish best practices for re-treatment when necessary. Herein, we review published clinical series and provide examples to highlight variables implicated in aneurysm persistence after treatment with flow diversion.

The Exchange-Free Technique: A Novel Technique for Enhancing Surpass Flow Diverter Placement

Background:

Following flow diverter placement, approximately 20% of intracranial aneurysms remain as residual aneurysms at 1 year. Device malapposition is a cause of residual aneurysms after flow diversion. We present a new and straightforward technique (exchange-free technique [EFT]) to enhance apposition of the surpass flow diverter (SFD), the only over-the-wire flow diverter currently available.

Materials and Methods:

We deployed laser-cut mini stents through the inner deployment catheter of the SFD. This maneuver was performed simply by withdrawing the micro-guidewire from its lumen and replacing it with a mini-stent (stents deliverable through microcatheters with inner diameter of 0.0165 inches), without a need to re-cross the deployed SFD or an exchange maneuver. All aneurysms in which this technique was utilized were retrospectively reviewed.

Results:

Twenty-eight patients (20 females) with 30 treated aneurysms were identified. The mean aneurysm diameter was 10.2 ± 6.6 mm. Technical success rate was 96.6% (29/30 aneurysms). There was no mortality or permanent morbidity related to the procedures. Except for the patient treated for an iatrogenic, surgery-related internal carotid artery pseudoaneurysm who died secondary to consequences of multiple surgeries, no cases of mortality or permanent morbidity were noted. Complete aneurysm occlusion rates were 78.2%, 82.1%, and 95.2% at 0–3, 3–6, and 9–12 months, respectively. None of the patients were re-treated.

Conclusion:

EFT is a simple and fast technique which was not associated with adverse effects in our series. The higher aneurysm obliteration rate obtained with EFT is probably the result of better wall apposition of the SFD.

A neurovascular high-frequency optical coherence tomography system enables in situ cerebrovascular volumetric microscopy

Intravascular imaging has emerged as a valuable tool for the treatment of coronary and peripheral artery disease; however, no solution is available for safe and reliable use in the tortuous vascular anatomy of the brain. Endovascular treatment of stroke is delivered under image guidance with insufficient resolution to adequately assess underlying arterial pathology and therapeutic devices. High-resolution imaging, enabling surgeons to visualize cerebral arteries' microstructure and micron-level features of neurovascular devices, would have a profound impact in the research, diagnosis, and treatment of cerebrovascular diseases. Here, we present a neurovascular high-frequency optical coherence tomography (HF-OCT) system, including an imaging console and an endoscopic probe designed to rapidly acquire volumetric microscopy data at a resolution approaching 10 microns in tortuous cerebrovascular anatomies. Using a combination of in vitro, ex vivo, and in vivo models, the feasibility of HF-OCT for cerebrovascular imaging was demonstrated.

Accuracy of optical coherence tomography imaging in assessing aneurysmal remnants after flow diversion

Background

Optical coherence tomography (OCT) is an ultra-high resolution real-time intravascular imaging method that is gaining interest in cerebrovascular applications.

Objective

To compare, in a rabbit elastase aneurysm model, digital subtraction angiography (DSA) and OCT as diagnostic tools for the assessment of aneurysmal remnants and baseline characteristics of aneurysms after flow diverter (FD) implantation.

Methods

With Institutional Animal Care and Use Committee approval, saccular aneurysms were created in 28 rabbits and treated with Derivo FDs. DSA was performed before, and immediately after, stent implantation. As a follow-up, DSA and OCT were performed 28 days after device implantation.

Results

DSA and OCT were successfully performed in 23 cases. OCT could not be achieved in 5 cases owing to navigational difficulties in the stent lumen with the OCT catheter. Residual aneurysms were significantly more often visible with OCT (18/23 (78%) than with DSA 12/23 (52%), p = 0.031).

Conclusion

OCT was more sensitive than conventional angiography for the assessment of residual aneurysms at 28 days after FD implantation in an animal model.

The Importance of Wall Apposition in Flow Diverters

BACKGROUND

It is assumed that high pore densities in flow diverters (FDs) are beneficial for intracranial aneurysm (IA) healing. However, various animal studies are not conclusive on the issue, suggesting that other factors are in play. One important factor might be wall apposition.

OBJECTIVE

To (1) determine the relationship between FD pore density and aneurysm occlusion, and (2) determine the relationship between FD wall apposition and aneurysm occlusion.

METHODS

Saccular aneurysms were microsurgically created in the aorta of 36 Wistar rats. Twelve rats received a low pore density FD (10 pores/mm2), 12 rats received a high pore density FD (23 pores/mm2), and the remaining 12 rats served as a control group. Six animals from each group were sacrificed 1 and 3 mo after surgery. We determined aneurysm occlusion, the number of struts not in contact with the aorta wall, and the average distance from malapposed struts to aorta wall through histology.

RESULTS

No significant differences were found in aneurysm occlusion between the low pore density and high pore density groups (P > .05) after 1 and 3 mo of follow-up. The average number of malapposed struts was lower for the occluded aneurysm group (4.4 ± 1.9) compared to the nonoccluded aneurysm group (7.7 ± 2.6, P < .01). The average distance between malapposed struts and parent artery wall was lower for the occluded aneurysm group (33.9 μm ± 11.5 μm) than for the nonoccluded aneurysm group (48.7 μm ± 18.8 μm, P < .05).

CONCLUSION

Wall apposition is more important than pore density for aneurysm occlusion.

Filament inadequate wall apposition of the different ends of flow diverters in the abdominal aorta of rabbits

BACKGROUND

Flow diverters (FDs) with flared ends (FEs) or straight ends (SEs) are used either alone or when overlapped to treat complex intracranial aneurysms. We evaluated filament inadequate wall apposition (IWA) of the FEs and SEs of FDs in vivo.

METHODS

A total of 24 FDs with FEs and SEs were placed in an overlapping manner in the abdominal aortae of six rabbits (two sets per rabbit). Digital subtraction angiography was performed immediately after stent insertion and three months later. The anatomical and histopathological aortic features at FEs and SEs were evaluated.

RESULTS

Angiography revealed no significant difference in terms of changes in arterial diameter between the FE and SE groups (p = 0.877). Gross anatomical evaluation revealed IWA of the different ends of FDs but no thrombi or bleeding, showing that the metallic filaments were not in touch with the vessel wall and nor had they penetrated the vessel wall. The filaments' IWA rates of FEs and SEs were 8.33% and 8.85%, respectively. The IWA rate at overlapping ends was lower than that at non-overlapping ends. The maximum neo-intimal thickness at FEs was greater than that at SEs (149.4 ± 48.9 and 98.6 ± 26.6 µm, respectively; p < 0.001).

CONCLUSIONS

Both the FEs and SEs of FDs can exhibit IMA. IWA events are reduced at the overlapped regions. On pathological evaluation, FEs increased neo-intimal thicknesses more than SEs did, but hyperplasia was minimal on angiography.

Agreement of intracranial vessel diameters measured on 2D and 3D digital subtraction angiography using an automatic windowing algorithm

BACKGROUND AND PURPOSE

Precise vessel measurement plays a major role in size selection of stents used for the treatment of intracranial aneurysms and became even more critical after the introduction of flow diverter stents. We assessed agreement between intracranial vessel diameters of aneurysm patients measured on 2D digital subtraction (2D DSA) and 3D volume rendering digital subtraction angiography (3D DSA) images using an automatic windowing algorithm.

MATERIALS AND METHODS

Ten patients with intracranial aneurysms were enrolled and 120 measurement points were selected on both 2D and 3D DSA images acquired by a biplane angiographic system. Automatic windowing was applied to the 3D DSA images. Inter-method agreement of vessel measurements on 2D and 3D DSA images was assessed by Bland Altman plots and intraclass correlation coefficients (ICC). Inter- and intra-rater agreement of measurements on 3D DSA images were assessed by ICCs.

RESULTS

The mean differences between measurements on 2D and 3D DSA images were 0.14mm for the ICA, and 0.18mm for the ACA and MCA, which is about the size of one 3D DSA image voxel. For ICA measurements, inter-method, inter-rater and intra-rater agreements were good or excellent (consistency and absolute ICC≥0.95). For ACA and MCA measurements, the inter-method, inter-rater and intra-rater agreements were also good or excellent (consistency ICC=0.94, 0.89 and 0.93, absolute ICC=0.83, 0.84 and 0.85 respectively).

CONCLUSIONS

Vessel diameters may be measured on 3D DSA images with sufficient reliability for clinical use when applying an automatic windowing algorithm.

Visualization of stent apposition after stent-assisted coiling of intracranial aneurysms using high resolution 3D fusion images acquired by C-arm CT

Purpose

We used an imaging technique based on 3-dimensional (3D) C-arm CT to assess the apposition of three types of stents after coiling of intracranial aneurysms.

Methods

All patients with intracranial aneurysms were considered who received stent-assisted coiling with Enterprise2, Neuroform EZ, or Neuroform Atlas stents confirmed by C-arm CT imaging at our institution between June 2015 and November 2017. A 3D digital subtraction angiography (DSA) scan for vessel imaging followed by a high-resolution cone beam CT (HR-CBCT) scan for coil and stent imaging was performed. The images were fused to obtain dual volume 3D fusion images. We investigated malapposition of the stent trunk (crescent sign) and of the stent edges (edge malapposition) and used the χ² statistic to test for an association with stent types. Inter-rater agreement between two raters was estimated using Cohen’s kappa statistics.

Results

We evaluated 75 consecutive cases. Enterprise2 stents were used in 22 cases, Neuroform EZ in 26, and Neuroform Atlas in 27 cases. By stent type, crescent sign was detected in 27% of Enterprise2, 8% of Neuroform EZ, and none of Neuroform Atlas stents (p=0.007), while edge malapposition was detected in 27% of Enterprise2, 58% of Neuroform EZ, and 30% of Neuroform Atlas stents (p=0.05). Excellent (κ=0.81) and good (κ=0.78) agreement between the raters was found for the detection of edge apposition and crescent sign, respectively.

Conclusion

Stent malapposition was clearly visualized by dual volume 3D imaging. The Neuroform Atlas stents showed good apposition even in vessels with strong curvature.

Aneurysm Remnants after Flow Diversion: Clinical and Angiographic Outcomes

BACKGROUND AND PURPOSE

Flow diversion is an established method to treat complex intracranial aneurysms. The natural history of flow-diversion treatment failure resulting in aneurysm remnants is not well-defined. We aimed to delineate the clinical and angiographic features of this entity.

MATERIALS AND METHODS

Review of a prospectively maintained Pipeline Embolization Device data base from inception to October 2017 was performed for aneurysms that demonstrated residual filling on follow-up imaging. Procedural and follow-up clinical details were recorded. Independent, blinded, angiographic assessment of occlusion was performed on the basis of the O'Kelly-Marotta scale. Aggregated outcomes were analyzed using the Fisher exact and Mann-Whitney U tests for categoric and continuous variables, respectively (statistical significance, α = .05).

RESULTS

During the study period, 283 sequential patients were treated; 87% (246/283) were women. The median patient age was 55 years (interquartile range, 47-65 years). Six-month follow-up imaging was available in 83.7% (237/283) of patients, which showed 62.4% (148/237) complete occlusion (class D, O'Kelly-Marotta grading scale). Adjunctive coiling (P = .06), on-label Pipeline Embolization Device use (P = .04), and multiple device constructs (P = .02) had higher rates of complete occlusion at 6 months. Aneurysm remnants were identified in 25 cases on long-term follow-up imaging (median, 16 months; interquartile range, 12-24 months). No patient with an aneurysm remnant after flow diversion presented with delayed rupture or other clinical sequelae, with a median clinical follow-up of 31 months (interquartile range, 23-33 months).

CONCLUSIONS

Aneurysm remnants after flow diversion are infrequent with minimal clinical impact. When appropriate, the presence of overlapping devices and possibly adjunctive coiling may result in higher rates of complete occlusion.

Fast acquisition cone-beam computed tomography: initial experience with a 10 s protocol

Background

Cone-beam computed tomography (CBCT) facilitates the acquisition of cross-sectional imaging in angiography suites using a rotational C-arm and digital flat panel detectors. The applications are numerous, including evaluation of implanted devices and localization of cerebrovascular lesions. We present and validate the clinical utility of an alternative fast CBCT acquisition protocol in the context of neurovascular device imaging.

Methods

Contrast-enhanced (CE)-CBCT images were acquired using a new 10 s protocol in a phantom head model, swine model, and in patients. The acquisition parameters of both the 10 s and 20 s protocols were exactly the same, except for fewer projections (250 projections in 10 s vs 500 projections in 20 s), resulting in reduced scan time. Image quality was measured quantitatively in a controlled phantom study and qualitatively by blinded reviewers. The latter was performed to assess the image quality of the 10 s protocol pertinent to the device visibility and its apposition to the parent artery.

Results

10 s CBCT images were comparable to 20 s CBCT in both phantom and animal studies. Of the 25 patient images, the reviewers agreed that they were able to discern the flow diverter struts and assess the apposition in all images. The overall rating for all 10 s images was 4.28 on a 5-point scale. No images were rated as less than 3, which was the average diagnostic quality. The ratings were concordant across three blinded reviewers (κ=0.411). Additionally, contrast and spatial resolution between 10 s and 20 s images were similar in non-human models.

Conclusions

CBCT images of neurovascular devices can be obtained successfully using a 10 s acquisition protocol. In addition, the 10 s protocol offers faster acquisition, thus allowing its use in awake patients and with an added advantage of lower radiation and contrast dose.

Open-cell stent and use of cone-beam CT enables a safe and effective coil embolization of true ophthalmic artery and anterior choroidal artery aneurysms with preservation of parent vessel: Clinical and angiographic results

Background Treatment of true ophthalmic artery (OA) or anterior choroidal artery (AChA) aneurysms with preservation of the parent vessel may be challenging. Flow diverters have limitations when dealing with branch vessels arising from the aneurysm sac. Visual loss or AChA territory infarcts have been reported both for surgical and endovascular treatment. Methods We evaluated the safety and efficacy of an open-cell design, laser-cut, self-expanding Nitinol stent, and use of cone-beam computed tomography (CBCT) for stent-assisted coil embolization. Results A total of seven patients with unruptured OA or AChA aneurysms were enrolled in this prospective small case study and the data were analyzed retrospectively. A complete obliteration was achieved in all aneurysms immediately post-intervention or at six-month follow-up without any evidence for recanalization at up to three-year follow-up. All patients tolerated the procedure well and there was no change in baseline modified Rankin Scale. Conclusions Our study suggests that specific features of an open-cell stent allow a safe and effective treatment of OA or AChA aneurysms with a high technical success rate and excellent mid-term angiographic and clinical outcome. CBCT is a useful intraoperative imaging tool.

Communicating malapposition of flow diverters assessed with optical coherence tomography correlates with delayed aneurysm occlusion

Background

Optical coherence tomography (OCT) is a high resolution intravascular imaging method that allows visualization of flow diverter struts and the vessel wall. In this study, malapposition of the flow diverter that continues into the neck of the aneurysm, named communicating malapposition (CM), was investigated as a potential factor for delayed aneurysm healing.

Methods

40 New Zealand White rabbits underwent elastase induced aneurysm creation, and were subsequently assigned to one of four treatment groups based on flow diverter type and administration of antiplatelet therapy. All animals underwent post device deployment balloon angioplasty and subsequent OCT to assess device/vessel apposition. The incidence of CM seen on OCT was assessed with a binary scoring system: 0–CM present; 1–CM absent. At 30 days, DSA was acquired to assess aneurysm healing. Aneurysm healing on terminal DSA was measured using a previously developed 5 point scale, with a score of 3 or 4 considered a positive outcome.

Results

All animals were grouped into a single cohort for analysis as no difference in the rate of CM or healing was seen in the four treatment groups. Significant interaction between the absence of CM and a positive outcome was confirmed by Fisher exact test (P=0.0034). Angioplasty was shown to treat 33% of the cases of CM seen at implant, and these treated cases overwhelmingly had a positive outcome (P<0.001).

Conclusion

The use of OCT to assess CM of flow diverters has been shown to be predictive of the 30 day healing rate of an animal model of aneurysms.

Acute thrombus formation on phosphorilcholine surface modified flow diverters

Purpose

Thromboembolic complications remain a limitation of flow diverting stents. We hypothesize that phosphorilcholine surface modified flow diverters (Pipeline Flex with Shield Technology, sPED) would have less acute thrombus formation on the device surface compared with the classic Pipeline Embolization device (cPED).

Methods

Elastase-induced aneurysms were created in 40 rabbits and randomly assigned to receive cPED or sPED devices with and without dual antiplatelet therapy (DAPT) (four groups, n=10/group). Angioplasty was performed to enhance apposition and create intimal injury for a pro-thrombotic environment. Both before and after angioplasty, the flow diverter was imaged with intravascular optical coherence tomography. The outcome measure was the number of predefined segments along the implant relative to the location of the aneurysm with a minimum of 0 (no clot formation) and maximum of 3 (all segments with thrombus). Clot formation over the device at ostia of branch arteries was assessed as either present or absent.

Results

Following angioplasty, the number of flow diverter segments with clots was significantly associated with the flow diverter (p<0.0001), but not with DAPT (p=0.3872) or aneurysm neck size (p=0.8555). The incidence rate for clots with cPED was 1.72 times more than with sPED. The clots on the flow diverter at the location corresponding to side branch ostia was significantly lower with sPED than with cPED (OR 0.180; 95% CI 0.044 to 0.734; p=0.0168), but was not associated with DAPT (p=0.3198).

Conclusion

In the rabbit model, phosphorilcholine surface modified flow diverters are associated with less thrombus formation on the surface of the device.

Treatment of an internal carotid artery aneurysm with a flow diverter through a double lumen balloon catheter

Background Double lumen balloon catheters (DLBCs) are currently used in the treatment of intracranial aneurysms, especially when involving balloon or stent-assisted coiling. The existing DLBCs allow the delivery of self-expandable stents but do not offer the possibility to deploy flow-diverters. Despite the increasing use and success of flow-diverters, there have been numerous reports of procedural complications such as early in-stent thrombosis or delayed distal embolization. It seems that these complications can be avoided by correct stent positioning and adequate wall apposition, achieved either by manoeuvres with the microguidewire and/or microcatheter or by performing balloon angioplasty following an exchange guidewire manoeuvre. Objective Report the use of a new DLBC able to deliver a flow-diverter. Methods A 41-year-old woman presented to our hospital with binocular horizontal diplopia for two weeks and reduced visual acuity. A left internal carotid artery aneurysm involving the cavernous and ophthalmic segments was found, with a maximum height of 19 mm and a broad 8 mm neck. It presented extra- and intra-dural components and the parent vessel was significantly narrowed. A decision was made to perform endovascular treatment of the aneurysm with placement of a flow diverter through a DLBC. Results Patency and adequate expansion of the flow diverter with evident intra-aneurysmal contrast stasis was observed in the final angiogram. No peri-procedural complications were observed. Conclusion This is a technical note demonstrating the feasibility of a new device to deploy a flow diverter, aiming to improve wall apposition and stent configuration without the need of additional devices or exchange manoeuvres.

In-stent Stenosis after p64 Flow Diverter Treatment

Purpose

There is limited information available on the incidence of in-stent stenosis (ISS) secondary to the use of flow-diverting stents in the intracranial vasculature. We sought to determine the incidence, severity, and clinical course of ISS on angiographic follow-up after treatment of saccular aneurysms with p64.

Methods

We retrospectively reviewed all patients who underwent treatment of a saccular (ruptured and unruptured) intracranial aneurysm with ≥1 p64 between 2011 and 2015. Fusiform aneurysms and dissections were excluded. Aneurysms with prior or concomitant saccular treatment (e. g., coiling, clipping) were included. Extradural targets and aneurysms with parent vessel implants other than p64 were excluded. ISS was assessed on follow-up angiography and defined as <50% (mild), 50–75% (moderate), or >75% (severe).

Results

In total, 205 patients (147 female, 71.7%; median age 57 years), with 223 saccular aneurysms were treated with p64 and had at least 9 months of digital subtraction angiography (DSA) follow-up completed. There was no DSA follow-up available in 8 patients. ISS of any degree at any time was recognized in 65/223 (29.1%) of all target aneurysms. The maximal degree of lumen loss was <50% in 40 lesions (17.9%), 50–75% in 19 lesions (8.5%), and >75% in 6 lesions (2.7%). ISS did not cause a focal neurological deficit in any patient. No progression from stenosis to occlusion was observed. Balloon angioplasty was performed in 1 lesion and was well tolerated. In 56 lesions (84.8%), a significant reduction of ISS occurred spontaneously, 2 mild stenoses remained stable, and for 6 lesions the long-term follow-up is pending.

Conclusion

Treatment with p64 is associated with an overall rate of 8.5% moderate ISS (50–75%) and 2.7% severe ISS (>75%), which is comparable with the rate of ISS reported in the literature for other flow diverting stents. There is a tendency for ISS to spontaneously improve over time.

Collar Sign in Incompletely Occluded Aneurysms after Pipeline Embolization: Evaluation with Angiography and Optical Coherence Tomography

BACKGROUND AND PURPOSE

Flow diversion with the Pipeline Embolization Device has emerged as an attractive treatment for cerebral aneurysms. Processes involved in aneurysm occlusion include changes in intra-aneurysmal hemodynamics and endothelialization of the device. Here, we call attention to a radiographic sign not previously reported that is detected in incompletely occluded aneurysms after treatment with the Pipeline Embolization Device at angiographic follow-up and referred to as the "collar sign."

MATERIALS AND METHODS

A retrospective review of all patients who underwent placement of a Pipeline Embolization Device for cerebral aneurysms between January 2014 and May 2016 was performed. All aneurysms found to show the collar sign at follow-up were included. Optical coherence tomography was performed in 1 case.

RESULTS

One hundred thirty-five aneurysms were treated in 115 patients. At angiographic follow-up, 17 (10.7%) aneurysms were found to be incompletely occluded. Ten (58.8%) of these aneurysms (average diameter, 7.9 ± 5.0 mm) were found to have the collar sign at angiographic follow-up (average, 5.5 ± 1.0 months). Four (40.0%) of the aneurysms underwent a second angiographic follow-up (average, 11.0 ± 0.9 months) after treatment, and again were incompletely occluded and showing the collar sign. Two patients underwent retreatment with a second Pipeline Embolization Device. Optical coherence tomography showed great variability of endothelialization at the proximal end of the Pipeline Embolization Device.

CONCLUSIONS

The collar sign appears to be indicative of endothelialization, but continued blood flow into the aneurysm. This is unusual given the processes involved in aneurysm occlusion after placement of the Pipeline Embolization Device and has not been previously reported.

Risk Factors for Ischemic Complications following Pipeline Embolization Device Treatment of Intracranial Aneurysms: Results from the IntrePED Study

BACKGROUND AND PURPOSE

Risk factors for acute ischemic stroke following flow-diverter treatment of intracranial aneurysms are poorly understood. Using the International Retrospective Study of Pipeline Embolization Device (IntrePED) registry, we studied demographic, aneurysm, and procedural characteristics associated with postoperative acute ischemic stroke following Pipeline Embolization Device (PED) treatment.

MATERIALS AND METHODS

We identified patients in the IntrePED registry with post-PED-treatment acute ischemic stroke. The rate of postoperative acute ischemic stroke was determined by demographics, comorbidities, aneurysm characteristics, and procedure characteristics (including anticoagulation use, platelet testing, number of devices used, sheaths, and so forth). Categoric variables were compared with χ(2) testing, and continuous variables were compared with the Student t test. Odds ratios and 95% confidence intervals were obtained by using univariate logistic regression. Multivariate logistic regression analysis was used to determine which factors were independently associated with postoperative stroke.

RESULTS

Of 793 patients with 906 aneurysms, 36 (4.5%) patients had acute ischemic stroke. Twenty-six (72.2%) strokes occurred within 30 days of treatment (median, 3.5 days; range, 0-397 days). Ten patients died, and the remaining 26 had major neurologic morbidity. Variables associated with higher odds of acute ischemic stroke on univariate analysis included male sex, hypertension, treatment of MCA aneurysms, treatment of fusiform aneurysms, treatment of giant aneurysms, and use of multiple PEDs. However, on multivariate analysis, the only one of these variables independently associated with stroke was treatment of fusiform aneurysms (OR, 2.74; 95% CI, 1.11-6.75; P = .03). Fusiform aneurysms that were associated with stroke were significantly larger than those not associated with stroke (mean, 24.5 ± 12.5 mm versus 13.6 ± 6.8 mm; P < .001).

CONCLUSIONS

Ischemic stroke following PED treatment is an uncommon-but-devastating complication. Fusiform aneurysms were the only variable independently associated with postoperative stroke.

Wall Apposition Is a Key Factor for Aneurysm Occlusion after Flow Diversion: A Histologic Evaluation in 41 Rabbits

BACKGROUND AND PURPOSE

Robust wall apposition for flow-diverter stents may be important for endothelialization. Using a large series of experimental aneurysms treated with the Pipeline Embolization Device, the objectives of this study were to 1) assess interobserver agreement for the evaluation of wall apposition on posttreatment DSA and evaluate its association with aneurysm occlusion, and 2) measure the relationship between wall apposition assessed with histology and aneurysm occlusion rate after treatment.

MATERIALS AND METHODS

Saccular aneurysms were created in 41 rabbits and treated with the Pipeline Embolization Device. DSA was performed just after the deployment of the device and at follow-up. Three investigators independently graded wall apposition on posttreatment DSA as good or poor. A histopathologist blinded to the angiographic results graded the wall apposition on histologic 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 76.9% and 84.0%, respectively, with an overall accuracy of 81.6%. In this experimental study, DSA was suboptimal to assess flow-diverter apposition, with moderate interobserver agreement and low accuracy.

CONCLUSIONS

Good wall apposition is strongly associated with complete occlusion after flow-diverter therapy. In this study, DSA was suboptimal for assessing wall apposition of flow-diverter stents. These findings suggest that improved tools for assessing flow diverter-stent wall apposition are highly relevant.

Intravascular optical coherence tomography for the evaluation of arterial bifurcations covered by flow diverters

Background and objective

Due to its high spatial resolution, intravascular optical coherence tomography (OCT) has been used as a valid method for in vivo evaluation of several types of coronary stents at straight lumen and bifurcation sites. We sought to evaluate its effectiveness for flow diverting stents deployed in arterial bifurcation sites involving jailing of a side branch.

Methods

Four large white swine were stented with flow diverting stents covering the right common carotid artery–ascending pharyngeal artery bifurcation. After 12 weeks of follow-up the animals were evaluated by digital subtraction angiography and intravascular OCT and subsequently sacrificed. Neointimal thickness on the parent arteries and the free segments of the stent were measured. The stented arteries were harvested and underwent scanning electron microscopy (SEM) imaging. Ostia surface values were measured with OCT three-dimensional (3D) reconstructions and SEM images.

Results

All endovascular procedures and OCT pullback runs were feasible. Stent apposition was satisfactory on the immediate post-stent OCT reconstructions. At 12-week controls, all stents and jailed branches were patent. Mean neointimal thickness was 0.11±0.04 mm on the free segments of the stent. The mean ostia surface at 12 weeks was 319 750±345 533 μm2 with 3D-OCT reconstructions and 351 198±396 355 μm2 with SEM image-derived calculations. Good correlation was found for ostia surface values between the two techniques; the values did not differ significantly in this preliminary study.

Conclusions

Intravascular OCT appears to be a promising technique for immediate and follow-up assessment of the orifice of arterial branches covered by flow diverting stents.