Comparison of intra-aneurysmal flow modification using optical flow imaging to evaluate the performance of Evolve and Pipeline flow diverting stents

Performance assessment of the Surpass Evolve flow diverter for the treatment of intracranial aneurysms: A systematic review and meta-analysis

BACKGROUND

The Surpass Evolve (SE) has emerged as a promising alternative treatment from the flow diverter series. The utilization of the SE has gradually increased, however, there is a scarcity of comprehensive data on the solidity of this technology in the endovascular treatment of intracranial aneurysms (IAs). This meta-analysis aimed to evaluate the safety and effectiveness of the SE flow diverter.

METHODS

A systematic literature search from inception to April 2024 was conducted across five databases for studies involving IAs treated with the SE. The primary effectiveness outcome was the proportion of complete aneurysm occlusion at the final follow-up, and the primary safety outcome comprised a composite of early and delayed complications. Subgroup analyses based on aneurysm size, anatomical location, and rupture status were also conducted.

RESULTS

Our analysis included nine studies with 645 patients and 722 IAs. Effectiveness outcomes revealed an overall complete aneurysm occlusion rate of 69% (95% confidence interval (CI) = 58%-78%; I2 = 72%) and a favorable aneurysm occlusion rate of 91% (95% CI = 82%-96%; I2 = 49%). Safety outcomes demonstrated an overall complications rate of 6% (95% CI = 3%-12%; I2 = 66%), with an early complications rate of 6% (95% CI = 4%-11%; I2 = 0%), and a delayed complications rate of 0% (95% CI = 0%-7%; I2 = 0%).

CONCLUSIONS

Our findings suggest a favorable outcome with a high rate of complete aneurysm occlusion at the last follow-up, with acceptable rates of neurological complications. Future research efforts should focus on larger, prospective studies with standardized outcome measures to further elucidate the clinical utility of the SE flow diverter in the management of IAs.

Comparison of Flow Reduction Efficacy of Nominal and Oversized Flow Diverters Using a Novel Measurement-assisted in Silico Method

PURPOSE

The high efficacy of flow diverters (FD) in the case of wide-neck aneurysms is well demonstrated, yet new challenges have arisen because of reported posttreatment failures and the growing number of new generation of devices. Our aim is to present a measurement-supported in silico workflow that automates the virtual deployment and subsequent hemodynamic analysis of FDs. In this work, the objective is to analyze the effects of FD deployment variability of two manufacturers on posttreatment flow reduction.

METHODS

The virtual deployment procedure is based on detailed mechanical calibration of the flow diverters, while the flow representation is based on hydrodynamic resistance (HR) measurements. Computational fluid dynamic simulations resulted in 5 untreated and 80 virtually treated scenarios, including 2 FD designs in nominal and oversized deployment states. The simulated aneurysmal velocity reduction (AMVR) is correlated with the HR values and deployment scenarios.

RESULTS

The linear HR coefficient and AMVR revealed a power-law relationship considering all 80 deployments. In nominal deployment scenarios, a significantly larger average AMVR was obtained (60.3%) for the 64-wire FDs than for 48-wire FDs (51.9%). In oversized deployments, the average AMVR was almost the same for 64-wire and 48-wire device types, 27.5% and 25.7%, respectively.

CONCLUSION

The applicability of our numerical workflow was demonstrated, also in large-scale hemodynamic investigations. The study revealed a robust power-law relationship between a HR coefficient and AMVR. Furthermore, the 64 wire configurations in nominal sizing produced a significantly higher posttreatment flow reduction, replicating the results of other in vitro studies.

Flow diverter retreatment for intracranial aneurysms: A meta-analysis of efficacy and feasibility

BACKGROUND

Recurrent intracranial aneurysm carries a risk of rupture and retreatment is often necessary. However, there is no consensus on the best retreatment modality of choice. Flow diverter has emerged as a promising option for this population in recent years. Given its high cost, patient selection to optimize outcomes is very important.

PURPOSE

To identify patient factors predisposing to failure of flow diverter retreatment.

METHOD

We conducted a systematic search on PubMed, Cochrane Library, Embase, Ovid/Medline, and ClinicalTrial.gov from 2000 to 2021. Studies regarding flow diverter retreatment of recurrent aneurysms were analyzed if they meet the inclusion criteria.

RESULTS

A total of twenty-six studies were identified. Among 374 patients retreated with flow diverters, about 0.86 [0.81; 0.92] were successfully occluded and only 0.06 [0.02; 0.10] had unfavorable neurological outcomes. Major complications included intracranial hemorrhage (n = 7), ischemic stroke or thromboembolic event (n = 12), and death (n = 2). In-stent stenosis was reported in 10 of the cases. Saccular aneurysms are associated with a higher occlusion rate while aneurysm location, size, status, and prior treatment modality have no significant impact on retreatment efficacy.

CONCLUSIONS

We demonstrated that flow diverter is an effective retreatment strategy except in patients with non-saccular aneurysms. It should be considered as a first-line option for patients with recurrent intracranial aneurysm.

Ongoing Geometric Remodeling of the Parent Artery After Flow-Diverter Stent Reconstruction in Cerebral Aneurysms: The Device Design Matters

OBJECTIVE

Configuration changes of the parent artery (PA) after flow-diverter (FD) stent reconstruction, caused by the bending force of the device, may have an additional role in aneurysm occlusion as a result of the secondary alteration of intra-aneurysmal hemodynamics related to the geometry alteration of the vessel. To determine the degree of PA deformation and aneurysm occlusion rates after deployment of 2 different types of FD.

METHODS

Patients treated with 2 different designs of cobalt-chromium braid (48 and 64 wire braid) structure FD were subject to analysis. Vascular angle changes at the level of the reconstructed segment immediately after FD deployment and at 1 year follow-up were measured and the potential relationship with aneurysmal occlusion rate was analyzed.

RESULTS

Forty-two patients harboring 48 aneurysms were included in the present study. The aneurysms were divided into side wall (85.4%) and bifurcation types (14.6%). Twenty-six aneurysms were treated using the Pipeline FD (48 wire braid; 54.2%) and 22 using the Evolve FD (64 wire braid; 45.8%). Of the 48 aneurysms, 42 (87.5%) met the primary end point of complete occlusion at 12 months. The median postdeployment angle change was 7.04°± 4.59° for the Pipeline and 5.05°± 2.49° for the Evolve, whereas the median 12 months follow-up angle change was 15.49°± 10.99° and 10.01°± 8.83°, respectively. PA angle changes were significantly higher in the bifurcation group compared with the side wall group both during procedure and at 12 months follow-up. Angle change had a statistically nonsignificant association with complete aneurysm occlusion.

CONCLUSIONS

PA deformation starts immediately after deployment and remodeling continues for 1 year after. Aneurysms located in the vessel bifurcation were more prone to PA straightening after FD deployment than were side wall aneurysms. Furthermore, Pipeline seemed to be more prone to inducing vascular deformation, compared with Evolve.

Multicenter study of the safety and effectiveness of intracranial aneurysm treatment with the p64MW-HPC flow modulation device

BACKGROUND AND PURPOSE

The new p64 flow diverter with hydrophilic polymer coating (HPC) was designed to reduce thrombogenicity. To date, it is unclear how antithrombogenic surface modifications affect neoendothelialization and thrombus formation in patients with unruptured intracranial aneurysms. The purpose of this study was to evaluate the safety and effectiveness of the p64MW-HPC in the treatment of unruptured aneurysms of small to giant size and of both the anterior and posterior circulation.

MATERIALS AND METHODS

Between March 2020 and October 2022 all patients with unruptured intracranial aneurysms treated with the p64MW-HPC were included at five neurovascular centers. Demographic data, aneurysm characteristics, antiplatelet therapy, procedural complications, and clinical and angiographic outcomes were recorded.

RESULTS

A total of 100 patients with 100 unruptured intracranial aneurysms met the inclusion criteria. Eighty-three aneurysms were classified as saccular, 12 aneurysms were fusiform, 4 aneurysms dissecting, and 1 aneurysm was blister-like. Dual antiplatelet therapy with Clopidogrel and Aspirin was given in 68 cases, and with Ticagrelor and Aspirin in 24 cases. Technical issues with deployment were encountered in 14 cases (torsion (n = 3), foreshortening (n = 8), and incomplete opening (n = 3)). Ischemic stroke occurred in a total of seven cases. In one patient a wire perforation and subsequent severe ICH occurred. Complete aneurysm occlusion at angiographic follow-up (mean time = 7 months) was seen in 73% and adequate occlusion in 93%.

CONCLUSION

This study is the largest multicenter study to date documenting the safety and effectiveness of the new antithrombogenic p64MW-HPC in the treatment of unruptured intracranial aneurysms of the anterior and posterior circulation.

Comparison of pipeline embolization device, flow re-direction endoluminal device and surpass flow diverters in the treatment of intracerebral aneurysms

OBJECTIVES

The use of flow diversion for the treatment of intracranial aneurysms has gained broad acceptance. Three flow-diverting stents are approved by the Food and Drug Administration for use in the United States. We sought to compare the outcomes and safety profiles between the three devices at our institution.

METHODS

A retrospective review of aneurysms treated with pipeline embolization device (PED), flow re-direction endoluminal device (FRED), and SURPASS was performed for aneurysms treated between 2018 and 2022 at our institution.

RESULTS

The study cohort consisted of 142 patients. Precisely, 86 aneurysms were treated with a pipeline, 33 aneurysms were treated with FRED, and 23 aneurysms were treated with SURPASS. The 1-year complete occlusion rates were 59.4%, 60%, and 65%, respectively (0.91). Linear regression models found that only adjunctive coiling predicted aneurysm occlusion at 6 months (p = 0.02), but this effect was lost at 1 year and beyond. There was no significant difference in acute thrombotic or acute hemorrhagic complications between the three cohorts. There was a higher rate of delayed hemorrhagic complications in the SURPASS cohort (10%) compared to the PED (1.3%) and FRED (0%) cohorts (p = 0.04). There was also a higher rate of in-stent stenosis in the SURPASS cohort (20%) compared to the PED (5%) and FRED (3.1%) cohorts (p < 0.01).

CONCLUSIONS

Treatment with PED, FRED, and SURPASS all resulted in similar complete occlusion rates at 6 months and 1 year. SURPASS was associated with higher in-stent stenosis as well as delayed hemorrhagic complications. Additional future studies evaluating the newest generation of flow-diverting stents with long-term follow-up will be necessary to make any definitive conclusions.

Procedural Software Toolkit in the Armamentarium of Interventional Therapies: A Review of Additive Usefulness and Current Evidence

Interventional radiology is a fast-paced specialty that uses many advanced and emerging technological solutions. Several procedural hardware and software products are available commercially. Image-guided procedural software helps save time and effort in interventionist practice and adds precision to the intraoperative decisions made by the end user. Interventional radiologists, including interventional oncologists, have access to a wide range of commercially available procedural software that can be integrated into their workflow. However, the resources and real-world evidence related to such software are limited. Thus, we performed a detailed review of the current resources available, such as software-related publications, vendors' multimedia materials (e.g., user guides), and each software's functions and features, to compile a resource for interventional therapies. We also reviewed previous studies that have verified the use of such software in angiographic suites. Procedural software products will continue to increase in number and usage; these will likely be advanced further with deep learning, artificial intelligence, and new add-ins. Therefore, classifying procedural product software can improve our understanding of these entities. This review significantly contributes to the existing literature because it highlights the lack of studies on procedural product software.

Reliability of using generic flow conditions to quantify aneurysmal haemodynamics: A comparison against simulations incorporating boundary conditions measured in vivo

BACKGROUND AND OBJECTIVES

Initiation, growth, and rupture of intracranial aneurysms are believed to be closely related to their local haemodynamic environment. While haemodynamics can be characterised by use of computational fluid dynamics (CFD), its reliability depends heavily upon accurate assumption of the boundary conditions. Herein, we compared the simulated aneurysmal haemodynamics obtained by use of generic boundary conditions against those obtained under flow conditions measured in vivo.

METHODS

We prospectively recruited 19 patients with intracranial aneurysms requiring 3-dimensional rotational angiography, during which blood pressure at the internal carotid artery was probed by catheter and flowrate measured by a dedicated software tool. Using these flow conditions measured in vivo, we quantified the aneurysmal haemodynamics for each patient by CFD, and then compared the results with those derived from a generic condition reported in the literature, in terms of the time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and percentage of the intra-aneurysmal flow (PIAF). In addition, the effects on aneurysmal haemodynamics of different outflow strategies (splitting method vs. Murray's Law) and simulation schemes (transient vs. steady-state) relative to each flow condition were also assessed.

RESULTS

Differences in the simulated TAWSS (-6.08 ± 10.64 Pa, p = 0.001), OSI (0.06 ± 0.13, p = 0.001), and PIAF (-0.05 ± 0.20, p = 0.012) between the patient-specific and generic boundary conditions were found to be statistically significant, in contrast to that in the RRT (49 ± 307 Pa^-1, p = 0.062). Outflow strategies did not yield statistically significant differences in any of the investigated parameters (all p > 0.05); rather, the resulting parameters were found to be in good correlations (all r > 0.71, p < 0.001). Difference between the aneurysmal TAWSS and the WSS derived from cycle-averaged flowrate condition was found to be minor (0.66 ± 1.36 Pa, p = 0.000), so was that between PIAFs obtained respectively from the transient and steady-state simulations (0.02 ± 0.05, p = 0.000).

CONCLUSIONS

Incorporating into simulation the patient-specific boundary conditions is critical for CFD to characterise aneurysmal haemodynamics, while outflow strategies may not introduce significant uncertainties. Steady-state simulation incorporating the cycle-averaged flow condition may produce unbiased WSS and PIAF compared to the transient analysis.

Surpass Evolve Flow Diverter for the Treatment of Intracranial Aneurysm: A Systematic Review

PURPOSE

This systematic review aims to summarize the evidence investigating the effectiveness and safety of the Surpass Evolve-Flow Diverter (SE-FD) to treat brain aneurysms.

METHOD

We searched MEDLINE, EMBASE, CINAHL, Web of Science, and Cochrane Library from January 2019 to 29 March 2022. Terms related to the "intracranial aneurysm" and "surpass evolve flow diverter" concepts were used to search the databases; Medical Subject Headings (MeSH) and reference hand search were also utilized.

RESULTS

The searches primarily identified 1586 documents. A total of five studies (four case series and one cohort) were included in this review. In the included studies, 192 (74 male and 118 females) patients with 198 aneurysms were involved. In total, 153 SE-FDs were used to treat 145 aneurysms. Complete occlusion was achieved in 69/145 (48%) cases and near-complete occlusion in 24/145 (17%) cases from aneurysms treated with SE-FD. Reported postoperative complications included stent thrombosis (n = 4 patients), hemorrhage (n = 5 patients), ischemia (n = 9 patients), and neurological complications (n = 12 patients). In total, four deaths were reported with only one related to the SE-FD procedure.

CONCLUSION

The results of this review are based on observational data, due to the absence of clinical trials. The findings of the included studies suggest that the effectiveness of the SE-FD procedure is lower than previous FDs but the safety is similar. The included studies also suggested that SE-FD has navigability and resistance to twisting, which makes the procedure an easier method to treat aneurysms that are proximal and distal to the circle of Willis deployment. This review highlights the urgency to conduct clinical trials to confirm these suggestions.

Rupture of an adjacent cerebral aneurysm following the deployment of a Pipeline embolization device: illustrative case

BACKGROUND

Although the Pipeline embolization device (PED) is effective for intracranial aneurysm treatment, its impact on the surrounding vascular structure is unknown.

OBSERVATIONS

A 71-year-old woman was incidentally found to have a simultaneous large posterior communicating artery aneurysm and an ipsilateral small anterior choroidal artery aneurysm. She underwent flow diversion therapy for both aneurysms with a PED, but the distal shortening of the PED after deployment led to the exposure of the anterior choroidal artery aneurysm. Follow-up angiography revealed complete obliteration of the posterior communicating artery aneurysm, but the anterior choroidal artery aneurysm remained. Three years after the endovascular surgery, the patient experienced a subarachnoid hemorrhage due to the rupture of the anterior choroidal artery aneurysm. Retrospective analysis of angiographic images revealed a change in the vascular geometry surrounding the ruptured aneurysm after PED deployment; this was further accompanied by an increase in the flow velocity inside the aneurysm.

LESSONS

Because PED use might induce the adverse effects on the adjacent uncovered aneurysm by changing the vascular geometry and hemodynamic stress, a cautious therapeutic strategy, such as proper placement of the stent and using a longer and appropriate-sized PED, should be chosen when deploying the PED.

Retrospective analysis of intracranial aneurysms after flow diverter treatment including color-coded imaging (syngo iFlow) as a predictor of aneurysm occlusion

PURPOSE

Flow Diverters (FD) have immensely extended the treatment of cerebral aneurysms in the past years. Complete aneurysm occlusion is a process that often takes a certain amount of time and is usually difficult to predict. Our aim was to investigate different syngo iFlow parameters in order to predict aneurysm occlusion.

METHODS

Between 2014 and 2018 patients with unruptured cerebral aneurysms treated with a FD were reviewed. Aneurysm occlusion and complication rates have been assessed.In addition, various quantitative criteria were assessed using syngo iFlow before, after the intervention, and after short and long-term digital subtraction angiography (DSA).

RESULTS

A total of 66 patients hosting 66 cerebral aneurysms were included in this study. 87.9% (n = 58) aneurysms in the anterior and 12.1% (n = 8) in the posterior circulation were treated. Adequate aneurysm occlusion at long-term follow-up (19.05 ± 15.1 months) was achieved in 90.9% (n = 60). Adequately occluded aneurysm revealed a significantly greater peak intensity delay (PI-D, p = 0.008) and intensity decrease ratio (ID-R, p < 0.001) compared to insufficiently occluded aneurysms. Increased intra-aneurysmal contrast agent intensity (>100%) after FD implantation resulted in an ID-R < 1, which was associated with aneurysm growth during follow-up DSA. Retreatment with another FD due to foreshortening and/or aneurysm growth was performed in 10.6% (n = 7). Overall morbidity and mortality rates were 1.5% (n = 1) and 0%.

CONCLUSION

The applied syngo iFlow parameters were found to be useful in predicting adequate aneurysm occlusion and foresee aneurysm growth, which might indicate the implantation of another FD.

Immediate flow-diversion characteristics of a novel primarily bioresorbable flow-diverting stent

OBJECTIVE

Flow-diverting stents with a resorbable component have significant theoretical benefits over full metal stents, although currently there are none in clinical use. In this study, the authors sought to determine the immediate flow-diversion characteristics of a novel primarily bioresorbable flow-diverting stent.

METHODS

Bioresorbable stents were deployed into glass tube models to determine porosity and pore density. In vitro flow diversion behavior was evaluated using high frame rate angiography under pulsatile flow conditions in a patient-specific silicone aneurysm model treated with the resorbable stent as well as the Surpass Evolve stent. In vivo flow diversion was characterized by deployment into 20 rabbit saccular aneurysm models, and grading was based on the O'Kelly-Marotta scale and the 4F-flow diversion predictive score.

RESULTS

Porosities and pore densities of the bioresorbable stent were in the flow-diverting range for all target vessel diameters. Quantified results of immediate angiography after placement of the bioresorbable stent into a silicone aneurysm model demonstrated greater flow diversion compared to the Evolve stent. Bioresorbable stent placement in saccular aneurysm models resulted in an immediate O'Kelly-Marotta grade of A3 or better and a 4F-flow diversion predictive score of 4 or better in all cases.

CONCLUSIONS

The bioresorbable stent has immediate flow-diversion characteristics that are comparable to commercially available metal stents. Longer-term studies are underway to determine the ability of the resorbable fibers to act as a neointimal scaffold and result in long-term aneurysm occlusion.

Diversion-p64: results from an international, prospective, multicenter, single-arm post-market study to assess the safety and effectiveness of the p64 flow modulation device

BACKGROUND

The use of flow diversion to treat intracranial aneurysms has increased in recent years.

OBJECTIVE

To assess the safety and angiographic efficacy of the p64 flow modulation device.

METHODS

Diversion-p64 is an international, prospective, multicenter, single-arm, study conducted at 26 centers. The p64 flow modulation device was used to treat anterior circulation aneurysms between December 2015 and January 2019. The primary safety endpoint was the incidence of major stroke or neurologic death at 3-6 months, with the primary efficacy endpoint being complete aneurysm occlusion (Raymond-Roy Occlusion Classification 1) on follow-up angiography.

RESULTS

A total of 420 patients met the eligibility criteria and underwent treatment with the p64 flow modulation device (mean age 55±12.0 years, 86.2% female). Mean aneurysm dome width was 6.99±5.28 mm and neck width 4.47±2.28 mm. Mean number of devices implanted per patient was 1.06±0.47, with adjunctive coiling performed in 14.0% of the cases. At the second angiographic follow-up (mean 375±73 days), available for 343 patients (81.7%), complete aneurysm occlusion was seen in 287 (83.7%) patients. Safety data were available for 413 patients (98.3%) at the first follow-up (mean 145±43 days) with a composite morbidity/mortality rate of 2.42% (n=10).

CONCLUSIONS

Diversion-p64 is the largest prospective study using the p64 flow modulation device. The results of this study demonstrate that the device has a high efficacy and carries a low rate of mortality and permanent morbidity.

Real-Time Evaluation of Blood Flow Patterns Using AneurysmFlow for an in vivo Abdominal Aortic Aneurysm Model

BACKGROUND

Many new tools for abdominal aortic aneurysm (AAA) rupture risk evaluation have been developed. These new tools need detailed hemodynamic information in AAA. However, hemodynamic data obtained from in vivo research are lacking. Thus, the objective of this study was to analyze blood flow patterns in an in vivo AAA model to acquire real-time hemodynamic information using AneurysmFlow, a novel flow evaluation system.

METHODS

Digital subtraction angiography images of patients who underwent endovascular aneurysm repair were analyzed using the visualization function of the AneurysmFlow to classify blood flow patterns as laminar or turbulent flow. The presence of boundary layer separation was also evaluated. The time taken for contrast medium to travel from the infrarenal aortic neck to aortic bifurcation was acquired to calculate the flow velocity. Associations between characteristics of aneurysm including lumen occupying ratio of intraluminal thrombus (ILT) and the hemodynamic flow pattern were evaluated.

RESULTS

A total of 37 AAA patients was enrolled. Their blood flow patterns were evaluated using the AneurysmFlow. Logistic regression analyses with lumen occupying ratio of ILT as an independent variable showed that the larger the lumen occupying ratio of ILT, the more likely the aneurysm was to show a laminar pattern (P = 0.03) and the more likely the boundary layer separation would not exist (P = 0.04). The flow velocity from the infrarenal aortic neck to the aortic bifurcation showed a positive association with the lumen occupying ratio of the ILT in linear regression analysis (P < 0.001).

CONCLUSION

Hemodynamic analysis of AAA with the AneurysmFlow using real-time individual patient models showed different flow patterns and flow velocities depending on ILT. This novel analytic approach using AneurysmFlow has potential to play an important role in obtaining clinically meaningful hemodynamic information of AAA.

Impact of Design and Deployment Technique on the Hydrodynamic Resistance of Flow Diverters : An in Vitro Experimental Study

PURPOSE

Despite the high efficacy of flow diverters (FD) in treating sidewall intracranial aneurysms, failures are reported. One of the physical factors determining efficacy is the flow reducing capacity of the FD that is currently unknown to the operator. Our aim was to measure the flow reducing capacity expressed as the hydrodynamic resistance (HR), the metallic surface area (MSA) and pore density (PD) of two different FD designs and quantitatively investigate the impact of sizing and the deployment technique on these parameters.

METHODS

Altogether 38 Pipeline (Medtronic) and P64 (Phenox) FD‑s were implanted in holder tubes by a neurointerventionist in nominally sized, oversized and longitudinally compressed or elongated manners. The tubes were placed in a flow model with the flow directed across the FD through a side hole on the tube. HR was expressed by the measured pressure drop as the function of the flow rate. Deployed length, MSA and PD were also measured and correlated with the HR.

RESULTS

Both PD and MSA changed with varying deployment length, which correlates well with the change in HR. Oversizing the device by 1 mm in diameter has reduced the HR on average to one fifth of the original value for both manufacturers.

CONCLUSION

This study demonstrates experimentally that different FD designs have different flow diverting capacities (HR). Parameters are greatly influenced by radial sizing and longitudinal compression or elongation during implantation. Our results might be useful in procedure planning, predicting clinical outcome, and in patient-specific numerical flow simulations.

Using angiographic parametric imaging-derived radiomics features to predict complications and embolization outcomes of intracranial aneurysms treated by pipeline embolization devices

BACKGROUND

Pipeline embolization devices (PEDs) have gained widespread popularity in the treatment of intracranial aneurysms (IAs). However, precise predictors of treatment outcomes are still lacking. This study aimed to use angiographic parametric imaging (API)-derived radiomics features to explore whether biomarkers extracted from immediate postprocedural digital subtraction angiography (DSA) were associated with complications and embolization outcomes of IAs treated with PED without adjunctive coils.

METHODS

Radiomic features were extracted from postprocedural DSA by API, and radiomics feature selection and radiomics score calculation were performed by the least absolute shrinkage and selection operator (LASSO) logistic regression. Angiographic findings and clinical characteristics were screened using stepwise multivariable logistic regression analysis to identify significant variables for predicting the complication endpoint. Radiomics feature selection and radiomics risk score (RadRS) calculations were performed by LASSO Cox regression. Univariate and multivariate Cox regression analyses were used to identify significant predictors for the occlusion endpoint.

RESULTS

We screened 281 observations for complications and 235 observations for embolization outcomes from IAs treated in our center using PED between June 2015 and July 2020. Multivariate regression analysis showed association of the radiomics score (p<0.01) and hypertension (p=0.04) with complications. RadRS (p<0.01), symptoms (p<0.01), and age (p=0.03) were predictors of embolization outcomes. Kaplan-Meier analysis revealed that symptomatic patients (p<0.01) and those with off-label IAs (p=0.03) had shorter intervals to complete occlusion.

CONCLUSIONS

Biomarkers extracted from immediate postprocedural DSA by API could be potential indicators for assessing treatment outcomes of IAs treated by PED without adjunctive coils.

Pulsatile Flow-Induced Fatigue-Resistant Photopolymerizable Hydrogels for the Treatment of Intracranial Aneurysms

An alternative intracranial aneurysm embolic agent is emerging in the form of hydrogels due to their ability to be injected in liquid phase and solidify in situ. Hydrogels have the ability to fill an aneurysm sac more completely compared to solid implants such as those used in coil embolization. Recently, the feasibility to implement photopolymerizable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels in vitro has been demonstrated for aneurysm application. Nonetheless, the physical and mechanical properties of such hydrogels require further characterization to evaluate their long-term integrity and stability to avoid implant compaction and aneurysm recurrence over time. To that end, molecular weight and polymer content of the hydrogels were tuned to match the elastic modulus and compliance of aneurysmal tissue while minimizing the swelling volume and pressure. The hydrogel precursor was injected and photopolymerized in an in vitro aneurysm model, designed by casting polydimethylsiloxane (PDMS) around 3D printed water-soluble sacrificial molds. The hydrogels were then exposed to a fatigue test under physiological pulsatile flow, inducing a combination of circumferential and shear stresses. The hydrogels withstood 5.5 million cycles and no significant weight loss of the implant was observed nor did the polymerized hydrogel protrude or migrate into the parent artery. Slight surface erosion defects of 2–10 μm in depth were observed after loading compared to 2 μm maximum for non-loaded hydrogels. These results show that our fine-tuned photopolymerized hydrogel is expected to withstand the physiological conditions of an in vivo implant study.

Implementation of computer simulation to assess flow diversion treatment outcomes: systematic review and meta-analysis

Introduction

Despite a decade of research into virtual stent deployment and the post-stenting aneurysmal hemodynamics, the hemodynamic factors which correlate with successful treatment remain inconclusive. We aimed to examine the differences in various post-treatment hemodynamic parameters between successfully and unsuccessfully treated cases, and to quantify the additional flow diversion achievable through stent compaction or insertion of a second stent.

Methods

A systematic review and meta-analysis were performed on eligible studies published from 2000 to 2019. We first classified cases according to treatment success (aneurysm occlusion) and then calculated the pooled standardized mean differences (SMD) of each available parameter to examine their association with clinical outcomes. Any additional flow diversion arising from the two common strategies for improving the stent wire density was quantified by pooling the results of such studies.

Results

We found that differences in the aneurysmal inflow rate (SMD −6.05, 95% CI −10.87 to −1.23, p=0.01) and energy loss (SMD −5.28, 95% CI −7.09 to −3.46, p<0.001) between the successfully and unsuccessfully treated groups were indicative of statistical significance, in contrast to wall shear stress (p=0.37), intra-aneurysmal average velocity (p=0.09), vortex core-line length (p=0.46), and shear rate (p=0.09). Compacting a single stent could achieve additional flow diversion comparable to that by dual-stent implantation.

Conclusions

Inflow rate and energy loss have shown promise as identifiers to discriminate between successful and unsuccessful treatment, pending future research into their diagnostic performance to establish optimal cut-off values.

Biomodex patient-specific brain aneurysm models: the value of simulation for first in-human experiences using new devices and robotics

Background

With the recent advent of advanced technologies in the field, treatment of neurovascular diseases using endovascular techniques is rapidly evolving. Here we describe our experience with pre-surgical simulation using the Biomodex EVIAS patient-specific 3D-printed models to plan aneurysm treatment using endovascular robotics and novel flow diverter devices.

Methods

Pre-procedural rehearsals with 3D-printed patient-specific models of eight cases harboring brain aneurysms were performed before the first in-human experiences. To assess the reliability of the experimental model, the characteristics of the aneurysms were compared between the patient and 3D models. The rehearsals were used to define the patient treatment plan, including technique, device sizing, and operative working projections.

Results

The study included eight patients with their respective EVIAS 3D aneurysm models. Pre-operative simulation was performed for the first in-human robotic-assisted neurovascular interventions (n=2) and new generation flow-diverter stents (n=6). Aneurysms were located in both the anterior (n=5) and posterior (n=3) circulation and were on average 11.0±6.5 mm in size. We found reliable reproduction of the aneurysm features and similar dimensions of the parent vessel anatomy between the 3D models and patient anatomy. Information learned from pre-surgical in vitro simulation are described in detail, including an improved patient treatment plan, which contributed to successful first in-world procedures with no intraprocedural complications.

Conclusions

Pre-procedural rehearsal using patient-specific 3D models provides precise procedure planning, which can potentially lead to greater operator confidence, decreased radiation dose and improvements in patient safety, particularly in first in-human experiences.