How precise is PreSize Neurovascular? Accuracy evaluation of flow diverter deployed-length prediction

OBJECTIVE

The use of flow-diverting stents has been increasingly important in intracranial aneurysm treatment. However, accurate sizing and landing zone prediction remain challenging. Inaccurate sizing can lead to suboptimal deployment, device waste, and complications. This study presents stent deployment length predictions offered in medical software (PreSize Neurovascular) that provides physicians with real-time planning support, allowing them to preoperatively "test" different devices in the patient's anatomy in a safe virtual environment. This study reports the software evaluation methodology and accuracy results when applied to real-world data from a wide range of cases and sources as a necessary step in demonstrating its reliability, prior to impact assessment in prospective clinical practice.

METHODS

Imaging data from 138 consecutive stent cases using the Pipeline embolization device were collected from 5 interventional radiology centers in the United Kingdom and retrospectively analyzed. Prediction accuracy was calculated as the degree of agreement between stent deployed length measured intraoperatively and simulated in the software.

RESULTS

The software predicted the deployed stent length with a mean accuracy of 95.61% (95% confidence interval [CI] 94.87%-96.35%), the highest reported accuracy in clinical stent simulations to date. By discounting 4 outlier cases, in which events such as interactions with coils and severe push/pull maneuvers impacted deployed length to an extent the software was not able to simulate or predict, the mean accuracy further increases to 96.13% (95% CI 95.58%-96.69%). A wide discrepancy was observed between labeled and measured deployed stent length, in some cases by more than double, with no demonstrable correlation between device dimensions and deployment elongation. These findings illustrate the complexity of stent behavior and need for simulation-assisted sizing for optimal surgical planning.

CONCLUSIONS

The software predicts the deployed stent length with excellent accuracy and could provide physicians with real-time accurate device selection support.

Treatment of an acutely ruptured complex fusiform middle cerebral artery aneurysm with flow diverting stenting and adjunctive coil embolization

This technical video demonstrates the treatment of an acutely ruptured, large, complex left fusiform middle cerebral artery (MCA) aneurysm with endovascular flow diversion with adjunctive coiling in a 27-year-old female. Two telescoping flow-diverting stents (Pipeline Flex) were placed, with partial coiling of a saccular portion of the aneurysm. Technical challenges, alternative treatment, intraoperative and postoperative antiplatelet management, vasospasm treatment, and clinical and radiographic follow-up are described. The video can be found here: https://stream.cadmore.media/r10.3171/2022.7.FOCVID2249.

Prediction of Cerebral Aneurysm Hemodynamics With Porous-Medium Models of Flow-Diverting Stents via Deep Learning

The interventional treatment of cerebral aneurysm requires hemodynamics to provide proper guidance. Computational fluid dynamics (CFD) is gradually used in calculating cerebral aneurysm hemodynamics before and after flow-diverting (FD) stent placement. However, the complex operation (such as the construction and placement simulation of fully resolved or porous-medium FD stent) and high computational cost of CFD hinder its application. To solve these problems, we applied aneurysm hemodynamics point cloud data sets and a deep learning network with double input and sampling channels. The flexible point cloud format can represent the geometry and flow distribution of different aneurysms before and after FD stent (represented by porous medium layer) placement with high resolution. The proposed network can directly analyze the relationship between aneurysm geometry and internal hemodynamics, to further realize the flow field prediction and avoid the complex operation of CFD. Statistical analysis shows that the prediction results of hemodynamics by our deep learning method are consistent with the CFD method (error function <13%), but the calculation time is significantly reduced 1,800 times. This study develops a novel deep learning method that can accurately predict the hemodynamics of different cerebral aneurysms before and after FD stent placement with low computational cost and simple operation processes.

Visceral Artery Aneurysms Embolization and Other Interventional Options: State of the Art and New Perspectives

Visceral artery aneurysms (VAAs) are rare, usually asymptomatic and incidentally discovered during a routine radiological examination. Shared guidelines suggest their treatment in the following conditions: VAAs with diameter larger than 2 cm, or 3 times exceeding the target artery; VAAs with a progressive growth of at least 0.5 cm per year; symptomatic or ruptured VAAs. Endovascular treatment, less burdened by morbidity and mortality than surgery, is generally the preferred option. Selection of the best strategy depends on the visceral artery involved, aneurysm characteristics, the clinical scenario and the operator's experience. Tortuosity of VAAs almost always makes embolization the only technically feasible option. The present narrative review reports state of the art and new perspectives on the main endovascular and other interventional options in the treatment of VAAs. Embolization techniques and materials, use of covered and flow-diverting stents and percutaneous approaches are accurately analyzed based on the current literature. Visceral artery-related considerations and targeted approaches are also provided and discussed.

Association Between Aneurysmal Haemodynamics and Device Microstructural Characteristics After Flow-Diversion Treatments With Dual Stents of Different Sizes: A Numerical Study

Objectives

Treating intracranial aneurysms with flow-diverting stents sometimes requires deployment of a second device. Herein we quantify the sizing effects of devices in dual-stent treatments upon the final stent microstructure and the post-treatment aneurysmal haemodynamics.

Methods

Fifteen sidewall ICA aneurysm geometries were included. Using a virtual stenting technique, we implanted either one or two stents for each aneurysm treatment considered, with each stent specified as one of two different sizes, yielding a total of two single-stent and fouir dual-stent treatment scenarios for each aneurysm. Three stent microstructural parameters and nine aneurysmal haemodynamic parameters were quantified and systematically compared across the 90 treatment scenarios.

Results

Deployment of a second stent further reduced the aneurysmal inflow rate (IR) and energy loss (EL) by, respectively, 14 ± 11% (p = 0.001) and 9 ± 12% (p = 0.056), relative to the untreated condition. Sizing effects of the earlier-deployed stent led to largest differences of 6.9% for the final IR reduction and 11.1% for the EL, whereas sizing effects from the later-deployed stent were minor (≤2.1%). The change in stent pore size was the only microstructural parameter demonstrating a strong correlation with the reduction in the post-treatment aneurysmal haemodynamics, in terms of the IR (r = 0.50, p < 0.001) and pressure drop (r = 0.63, p < 0.001).

Conclusion

Size of the earlier-deployed stent has substantial effects on the final haemodynamic outcomes after dual-stent treatment. The average pore size of stent wires at the aneurysm orifice shows promise as a potential index for predicting the efficacy of flow-diversion treatments.

[Resection and correction of the common carotid artery to enable an endovascular approach for treatment of a giant ICA aneurysm (a case report and literature review)]

The article reports a clinical case of endovascular treatment of a female patient with a giant aneurysm of the cavernous internal carotid artery complicated by gross ipsilateral bending of the proximal third of the common carotid artery. To ensure an adequate endovascular approach to the aneurysm, open repair of the common carotid artery and elimination of its bending were performed at the first stage. This enabled successful placement of a flow-diverting stent into the internal carotid artery at the aneurysm level at the second stage, resulting in good technical and clinical outcomes. We discuss the technical aspects of performed interventions and the opportunity of using this approach in patients who need endovascular interventions that are complicated by anatomical-morphological changes in the brachiocephalic arteries.

Novel use of flow diversion for the treatment of aneurysms associated with arteriovenous malformations

The use of flow-diverting stents for intracranial aneurysms has become more prevalent, and flow diverters are now routinely used beyond their initial scope of approval at the proximal internal carotid artery. Although flow diversion for the treatment of cerebral aneurysms is becoming more commonplace, there have been no reports of its use to treat flow-related cerebral aneurysms associated with arteriovenous malformations (AVMs). The authors report the cases of 2 patients whose AVM-associated aneurysms were managed with flow diversion. A 40-year-old woman presented with a history of headaches that led to the identification of an unruptured Spetzler-Martin Grade V, right parietooccipital AVM associated with 3 aneurysms of the ipsilateral internal carotid artery. Initial attempts at balloon-assisted coil embolization of the aneurysms were unsuccessful. The patient underwent placement of a flow-diverting stent across the diseased vessel; a 6-month follow-up angiogram demonstrated complete occlusion of the aneurysms. In the second case, a 57-year-old man presented with new-onset seizures, and an unruptured Spetzler-Martin Grade V, right frontal AVM associated with an irregular, wide-necked anterior communicating artery aneurysm was identified. The patient underwent placement of a flow-diverting stent, and complete occlusion of the aneurysm was observed on a 7-month follow-up angiogram. These 2 cases illustrate the potential for use of flow diversion as a treatment strategy for feeding artery aneurysms associated with AVMs. Because of the need for dual antiplatelet medications after flow diversion in this patient population, however, this strategy should be used judiciously.

Role of terminal and anastomotic circulation in the patency of arteries jailed by flow-diverting stents: from hemodynamic changes to ostia surface modifications

OBJECTIVE The outcome for jailing arterial branches that emerge near intracranial aneurysms during flow-diverting stent (FDS) deployment remains controversial. In this animal study, the authors aimed to elucidate the role of collateral supply with regard to the hemodynamic changes and neointimal modifications that occur from jailing arteries with FDSs. To serve this purpose, the authors sought to quantify 1) the hemodynamic changes that occur at the jailed arterial branches immediately after stent placement and 2) the ostia surface values at 3 months after stenting; both parameters were investigated in the presence or absence of collateral arterial flow. METHODS After an a priori power analysis, 2 groups (Group A and Group B) were created according to an animal flow model for terminal and anastomotic arterial circulation; each group contained 7 Large White swine. Group A animals possessed an anastomotic-type arterial configuration to supply the territory of the right ascending pharyngeal artery (APhA), while Group B animals possessed a terminal-type arterial configuration to supply the right APhA territory. Subsequently, all animals underwent FDS placement, thereby jailing the right APhAs. Mean flow rates and velocities inside the jailed branches were quantified using time-resolved 3D phase-contrast MR angiography before and after stenting. Three months after stent placement, the jailed ostia surface values were quantified on scanning electron micrographs. The data were analyzed using descriptive statistics and group comparisons with parametric and nonparametric tests. RESULTS The endovascular procedures were feasible, and there were no findings of in situ thrombus formation on postprocedural optical coherence tomography or ischemia on postprocedural diffusion-weighted imaging. In Group A, the mean flow rate values at the jailed right APhAs were reduced immediately following stent placement as compared with values obtained before stent placement (p = 0.02, power: 0.8). In contrast, the mean poststenting flow rates for Group B remained similar to those obtained before stent placement. Three months after stent placement, the mean ostia surface values were significantly higher for Group B (527,911 ± 306,229 μm²) than for Group A (89,329 ± 59,762 μm²; p < 0.01, power: 1.00), even though the initial dimensions of the jailed ostia were similar between groups. A statistically significant correlation was found between groups (A or B), mean flow rates after stent placement, and ostia surface values at 3 months. CONCLUSIONS When an important collateral supply was present, the jailing of side arteries with flow diverters resulted in an immediate and significant reduction in the flow rate inside these arteries as compared with the prestenting values. In contrast, when competitive flow was absent, jailing did not result in significant flow rate reductions inside the jailed arteries. Ostium surface values at 3 months after stent placement were significantly higher in the terminal group of jailed arteries (Group B) than in the anastomotic group (Group A) and strongly correlated with poststenting reductions in the velocity value.

Scanning electron microscopy for flow-diverting stent research: technical tips and tricks

Flow-diverting (FD) stents represent a new concept in the treatment of intracranial aneurysms with challenging anatomical dispositions. Having been introduced to clinical practice only in the last 5 years and featuring complex mechanisms of action, they are still under research. Scanning electron microscopy, as part of an animal research protocol, provides detailed surface observations of neointimal healing at the aneurysm's neck, as well as covered side branch ostia, allowing for the confirmation of scientific hypotheses and observations. Technical adaptations of preparation protocols are presented based on a pilot study on Large White pigs, stented with FD stents at carotid bifurcations.

Personalizing flow-diverter intervention for cerebral aneurysms: from computational hemodynamics to biochemical modeling

This paper presents the computational modeling of a variety of flow-diverting stents, deployed in a number of patient-specific aneurysm geometries. We consider virtual device deployment and hemodynamics as well as thrombus formation, with the scope to assess pre-operatively the efficacy of specific devices in treating particular aneurysms. An algorithm based on a linear and torsional spring analogy is developed for the fast virtual deployment of stents and similar minimally invasive devices in patient-specific vessel geometries. The virtual deployment algorithm is used to accurately deploy a total of four stent designs in three aneurysm geometries. A variety of different flow-diverting stent designs, representing the commercially available and the entirely novel, are presented, varying in both mesh design and porosity. Transient computational hemodynamics simulations are performed on multiple patient-specific geometries to predict the reduction in aneurysm inflow after the deployment of each device. Further, a thrombosis initiation and growth model is implemented, coupled with the hemodynamic computations. Hemodynamic simulations show large variations in flow reduction between devices and across different aneurysm geometries. The industry standard of flow-diverters with 70% porosity, assumed to offer the best compromise in flexibility and flow reduction, is challenged in at least one aneurysm geometry.