Evaluation of Two Fast Virtual Stenting Algorithms for Intracranial Aneurysm Flow Diversion

2020 ◽  
Vol 17 (1) ◽  
pp. 58-70 ◽  
Author(s):  
Saeb R. Lamooki ◽  
Vincent M. Tutino ◽  
Nikhil Paliwal ◽  
Robert J. Damiano ◽  
Muhammad Waqas ◽  
...  
Keyword(s):  
A Priori ◽  
Flow Diverter ◽  
Post Treatment ◽  
Patient Specific ◽  
Clinical Tool ◽  
Neck Size ◽  
Aneurysm Neck ◽  
Flow Modification ◽  
Stent Expansion ◽  
Stent Geometry

Background: Endovascular treatment of intracranial aneurysms (IAs) by flow diverter (FD) stents depends on flow modification. Patient-specific modeling of FD deployment and computational fluid dynamics (CFD) could enable a priori endovascular strategy optimization. We developed a fast, simplistic, expansion-free balls-weeping algorithm to model FDs in patientspecific aneurysm geometry. However, since such strong simplification could result in less accurate simulations, we also developed a fast virtual stenting workflow (VSW) that explicitly models stent expansion using pseudo-physical forces. Methods: To test which of these two fast algorithms more accurately simulates real FDs, we applied them to virtually treat three representative patient-specific IAs. We deployed Pipeline Embolization Device into 3 patient-specific silicone aneurysm phantoms and simulated the treatments using both balls-weeping and VSW algorithms in computational aneurysm models. We then compared the virtually deployed FD stents against experimental results in terms of geometry and post-treatment flow fields. For stent geometry, we evaluated gross configurations and porosity. For post-treatment aneurysmal flow, we compared CFD results against experimental measurements by particle image velocimetry. Results: We found that VSW created more realistic FD deployments than balls-weeping in terms of stent geometry, porosity and pore density. In particular, balls-weeping produced unrealistic FD bulging at the aneurysm neck, and this artifact drastically increased with neck size. Both FD deployment methods resulted in similar flow patterns, but the VSW had less error in flow velocity and inflow rate. Conclusion: In conclusion, modeling stent expansion is critical for preventing unrealistic bulging effects and thus should be considered in virtual FD deployment algorithms. Also endowed with its high computational efficiency and superior accuracy, the VSW algorithm is a better candidate for implementation into a bedside clinical tool for FD deployment simulation.

Phototherapy Enhanced Exclusion of Aneurysms From the Cerebral Circulation

2013 ◽  
Author(s):  
Baruch B. Lieber ◽  
Chander Sadasivan ◽  
David J. Fiorella ◽  
Henry H. Woo
Keyword(s):  
Thrombus Formation ◽  
A Priori ◽  
Flow Diverter ◽  
Experimental Models ◽  
Neointimal Formation ◽  
Fresh Blood ◽  
Aneurysm Neck ◽  
The Past ◽  
Neointimal Proliferation ◽  
Flow Diverters

Accumulated experience using flow diverters in humans suggests that complete cure of the aneurysm is usually a protracted process that can last up to twelve months [1]. While it is well established that a properly designed flow diverter serves as a scaffold for neointimal proliferation, the process of its formation over the aneurysm neck is delayed until the aneurysm cavity itself is occluded by a thrombus, negating flow of fresh blood through the neck, and thus allowing the neointimal formation to bridge the aneurysm neck. The notion that induction of some injury to the luminal surface of the aneurysmal tissue, particularly to the endothelium, may result in a healing response that is faster than just placing a flow diverter and waiting for thrombus formation within the aneurysm has been tried in the past using various experimental models. Some of the injuries to the aneurysm tissue that have been tried in the past include mechanical scraping, thermal heating and UV irradiation. All these attempts, while showing that hastening the thrombus formation is feasible, have not resulted in any success due to the fact that the processes that were tried suffered from lack of proper control to be implemented in actual aneurysmal tissue that is weakened and diseased a priori.

scholarly journals Acute thrombus formation on phosphorilcholine surface modified flow diverters

2017 ◽  
Vol 10 (4) ◽  
pp. 406-411 ◽  
Author(s):  
Miklos Marosfoi ◽  
Frederic Clarencon ◽  
Erin T Langan ◽  
Robert M King ◽  
Olivia W Brooks ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Rabbit Model ◽  
Flow Diverter ◽  
Side Branch ◽  
Clot Formation ◽  
Neck Size ◽  
Aneurysm Neck ◽  
Before And After ◽  
Surface Modified ◽  
Flow Diverters

PurposeThromboembolic 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).MethodsElastase-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.ResultsFollowing 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).ConclusionIn the rabbit model, phosphorilcholine surface modified flow diverters are associated with less thrombus formation on the surface of the device.

Computational Hemodynamic Evaluation of Two Clinical Flow-Diverter Treatment Strategies: Overlapping Stents vs. Dense Compaction of a Single Stent

2014 ◽  
Author(s):  
Robert Damiano ◽  
Jianping Xiang ◽  
Adnan Siddiqui ◽  
Hui Meng
Keyword(s):  
Treatment Strategies ◽  
Flow Diverter ◽  
Hemodynamic Effect ◽  
Coverage Rate ◽  
Patient Specific ◽  
Test Cases ◽  
Strongly Correlated ◽  
Aneurysm Neck ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Diverters

We employed computational fluid dynamics (CFD) and finite element method (FEM) to investigate the hemodynamic effect of two flow-diversion strategies of cerebral aneurysm treatment: overlapping stents and dense compaction of a single stent. Three representative patient-specific aneurysms were used as test cases, and flow diverters were virtually deployed into the models. Aneurysmal hemodynamic modification by flow diverters is strongly correlated with the metal coverage rate across the aneurysm neck, and not uniquely determined by FD deployment strategies. Fusiform aneurysms may be more favorable for achieving dense compaction for increased metal coverage rate than saccuclar aneurysms. To induce high flow reduction, the overlapping strategy may be more suitable for sidewall aneurysms, and the dense compaction strategy for fusiform aneurysms.

scholarly journals Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saurabhi Samant ◽  
Wei Wu ◽  
Shijia Zhao ◽  
Behram Khan ◽  
Mohammadali Sharzehee ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Experimental Studies ◽  
Patient Specific ◽  
Wall Structure ◽  
Left Main ◽  
Element Analysis ◽  
Stent Expansion ◽  
Radial Strength ◽  
Different Diameters

AbstractLeft main (LM) coronary artery bifurcation stenting is a challenging topic due to the distinct anatomy and wall structure of LM. In this work, we investigated computationally and experimentally the mechanical performance of a novel everolimus-eluting stent (SYNERGY MEGATRON) purpose-built for interventions to large proximal coronary segments, including LM. MEGATRON stent has been purposefully designed to sustain its structural integrity at higher expansion diameters and to provide optimal lumen coverage. Four patient-specific LM geometries were 3D reconstructed and stented computationally with finite element analysis in a well-validated computational stent simulation platform under different homogeneous and heterogeneous plaque conditions. Four different everolimus-eluting stent designs (9-peak prototype MEGATRON, 10-peak prototype MEGATRON, 12-peak MEGATRON, and SYNERGY) were deployed computationally in all bifurcation geometries at three different diameters (i.e., 3.5, 4.5, and 5.0 mm). The stent designs were also expanded experimentally from 3.5 to 5.0 mm (blind analysis). Stent morphometric and biomechanical indices were calculated in the computational and experimental studies. In the computational studies the 12-peak MEGATRON exhibited significantly greater expansion, better scaffolding, smaller vessel prolapse, and greater radial strength (expressed as normalized hoop force) than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY (p < 0.05). Larger stent expansion diameters had significantly better radial strength and worse scaffolding than smaller stent diameters (p < 0.001). Computational stenting showed comparable scaffolding and radial strength with experimental stenting. 12-peak MEGATRON exhibited better mechanical performance than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY. Patient-specific computational LM stenting simulations can accurately reproduce experimental stent testing, providing an attractive framework for cost- and time-effective stent research and development.

scholarly journals Mathematical analysis of the influence of brain metabolism on the BOLD signal in Alzheimer’s disease

2017 ◽  
Vol 38 (2) ◽  
pp. 304-316 ◽  
Author(s):  
Felix Winter ◽  
Catrin Bludszuweit-Philipp ◽  
Olaf Wolkenhauer
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Resting State Fmri ◽  
Blood Oxygen Level Dependent ◽  
Peak Height ◽  
Brain Dysfunction ◽  
Patient Specific ◽  
Theoretic Approach ◽  
Hemodynamic Response Function ◽  
Clinical Tool

Blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) is a standard clinical tool for the detection of brain activation. In Alzheimer’s disease (AD), task-related and resting state fMRI have been used to detect brain dysfunction. It has been shown that the shape of the BOLD response is affected in early AD. To correctly interpret these changes, the mechanisms responsible for the observed behaviour need to be known. The parameters of the canonical hemodynamic response function (HRF) commonly used in the analysis of fMRI data have no direct biological interpretation and cannot be used to answer this question. We here present a model that allows relating AD-specific changes in the BOLD shape to changes in the underlying energy metabolism. According to our findings, the classic view that differences in the BOLD shape are only attributed to changes in strength and duration of the stimulus does not hold. Instead, peak height, peak timing and full width at half maximum are sensitive to changes in the reaction rate of several metabolic reactions. Our systems-theoretic approach allows the use of patient-specific clinical data to predict dementia-driven changes in the HRF, which can be used to improve the results of fMRI analyses in AD patients.

Abstract 120: Surpass Flow Diverter for Endovascular Treatment of Intracranial Aneurysms - A Multicenter Preliminary Clinical and Angiographic Experience in 161 Patients with 186 Aneurysms

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Ajay K Wakhloo ◽  
Pedro Lylyk ◽  
Joost de Vries ◽  
Matthew J Gounis ◽  
Alexandra Biondi ◽  
...  
Keyword(s):  
Intracranial Aneurysms ◽  
Experimental Studies ◽  
Flow Diverter ◽  
Posterior Circulation ◽  
Parent Artery ◽  
Anterior Circulation ◽  
Neck Size ◽  
Wide Range ◽  
New Generation

Objective: Validated through experimental studies a new generation of flow diverters (Surpass™ FD) was evaluated for treatment of intracranial aneurysms (IA). We present our multicenter preliminary clinical and angiographic experience. METHODS: To achieve the calculated flow disruption between the parent artery and aneurysm for thrombosis, single FDs were placed endovascularly in parent arteries. Implants measured 2.5-5.3mm in diameter with a length of 10-80mm. Patients were enrolled harboring a wide range large and giant wide-neck, fusiform and multiple small and blister-type aneurysm. Clinical and angiographic follow-up were performed at 1-3, 6, and 12 months. RESULTS: A total of 186 consecutive IA in 161 patients (mean age 57.1 years) were treated at 33 centers. Fifty-three aneurysms were smaller than 5 mm, 64 were 5-9.9mm in diameter, 47 were 10-20mm in diameter, and 22 were larger than 20mm (10.4±0.7mm, neck size 6.0±0.5mm [mean±SEM]) . The aneurysms originated in 63.4% from the internal carotid artery; 22% and 14.5% of the lesions were located in the anterior circulation distal to Circle of Willis and posterior circulation respectively. Technical success was achieved in 182 aneurysms (98%); average number of devices used per aneurysm was 1.05. Permanent morbidity and mortality during the follow-up period of mean 8.4months (range 1-24 months) including periprocedural complications for patients with aneurysms of the anterior circulation were encountered in 5 (3.7%) and 2 (1.5 %) patients respectively and 1 (3.7%) and 4 (14.8%) respectively for patients with aneurysms of the posterior circulation location. One-hundred-ten patients (70.5%) harboring 127 (70.2%) were available for clinical and angiographic follow-up and showed a complete or near complete aneurysm occlusion in 63 (81.8%) of the ICA. Aneurysms of the ICA≥10mm that were completely covered by FD and not previously stent-treated with a minimum of 6 months follow-up available in 16 patients showed a complete obliteration in 81.3% (n=13) and >90% occlusion in remaining 3 patients. CONCLUSION: Preliminary data demonstrate high safety and efficacy of a new generation of FD for a wide range of IA of the anterior and posterior circulation with a single implant.

Quantitation of intracranial aneurysm neck size from diagnostic angiograms based on a biomathematical model

1995 ◽  
Vol 17 (5) ◽  
pp. 322-328 ◽  
Author(s):  
George J. Hádemenos ◽  
Tarik F. Massoud ◽  
Fernando Viñuela
Keyword(s):  
Intracranial Aneurysm ◽  
Neck Size ◽  
Aneurysm Neck

scholarly journals The effect of microbiota-based investigational drug RBX2660 on the gut microbiome and resistome revealed by a placebo-controlled clinical trial

2020 ◽  
Author(s):  
Suryang Kwak ◽  
JooHee Choi ◽  
Tiffany Hink ◽  
Kimberly A. Reske ◽  
Kenneth Blount ◽  
...  
Keyword(s):  
Gut Microbiome ◽  
Post Treatment ◽  
Patient Specific ◽  
Controlled Clinical Trial ◽  
Investigational Drug ◽  
Double Blind ◽  
Significant Recovery ◽  
Clostridioides Difficile ◽  
Metabolic Functions ◽  
Clostridioides Difficile Infection

Abstract Background Intestinal microbiota restoration can be achieved by replacing a subject’s perturbed microbiota with that of a healthy donor. Recurrent Clostridioides difficile infection (rCDI) is one key application of such treatment. Another application of interest is depletion of antibiotic resistant genes (ARGs) and organisms (AROs). In this study, we investigated fecal specimens from a multicenter, randomized, double-blind, placebo-controlled phase 2b study of microbiota-based investigational drug RBX2660. Patients were administered either placebo, 1 dose of RBX2660 and 1 placebo, or 2 doses of RBX2660 via enema and longitudinally tracked for changes in their microbiome and antibiotic resistome. Results All patients exhibited significant recovery of gut microbiome diversity and decrease of ARG abundance during the first 7 days post-treatment. However, the microbiome and resistome shifts towards healthier configurations were more significant and longer lasting in RBX2660 recipients compared to placebo. We identified 18 taxa and 21 metabolic functions distinguishing the baseline microbiome of non-transplanted patients, and the majority of features were correlated to intrinsic vancomycin resistance. We also identified 7 patient-specific and 3 RBX2660-specific ARGs and tracked their dynamics post treatment. Whole genome sequencing of AROs cultured from RBX2660 product and patient samples indicate ARO eradication in patients via RBX2660 administration, but also, to a lesser extent, introduction of RBX2660-derived AROs. Conclusions By including a placebo group, we distinguished the effects of RBX2660 from baseline post-antibiotic microbiome dynamics. Antibiotic discontinuation alone resulted in significant recovery of gut microbial diversity and reduced ARG abundance, but RBX2660 administration more rapidly and completely changed the composition of patients’ microbiome, resistome, and ARO colonization by transplanting RBX2660 microbiota into the recipients. Although ARGs and AROs were transmitted through RBX2660, the resistome post-RBX2660 more closely resembled that of the administered product—a proxy for the donor—than an antibiotic perturbed state.

Abstract 482: Attachment Site Curvature of Thoracic Endografts is Correlated to Adjacent Aortic Wall Stress and Stress Distribution

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Nathan Couper ◽  
Michael Richards ◽  
Ankur Chandra
Keyword(s):  
Stress Distribution ◽  
Aortic Root ◽  
Mean Curvature ◽  
Aortic Wall ◽  
Attachment Site ◽  
Wall Stress ◽  
Patient Specific ◽  
Clinical Tool ◽  
Element Analysis ◽  
Clinical Series

INTRODUCTION: TEVAR has been seen to cause acute and chronic stent-induced tears of the adjacent aortic wall after treatment in 10-25% of cases with increasing frequency as the stent is placed closer to the aortic valve. The underlying cause for these tears and the ability to predict their occurrence is poorly understood. We hypothesize the cause of these tears is related to stent-induced changes in the adjacent aortic wall which could be quantified and predicted through finite element analysis (FEA) of stent-aorta interface. METHODS: Abaqus TM was used to resolve the FEA model of the stent-aorta interface in three configurations. The maximum principal stress in the vessel wall was averaged over the volume around the stent attachment point and the curvature of the stent was calculated at both the distal and proximal ends. (Figure 1). RESULTS: As the curvature of the attachment site increased, an increase in adjacent aortic wall stress was noted. These ranged from mean curvature (1/m) of 0.1 with wall stress of 49kPa for the distal attachment, position #2 to mean curvature of 6.7 and wall stress of 82kPa for the distal attachment site in position #3. There was an increase in maximum stress distribution as the TEVAR approached the aortic root of 104kPa, 109kPa, and 112kPa for positions 1-3 repectively. CONCLUSIONS: An increase in adjacent aortic wall stress and stress distribution was noted as TEVAR were placed closer to the aortic root which corresponds to the increase in stent-induced aortic tears observed in clinical series. This approach provides the basis for a predictive clinical tool to allow for patient-specific TEVAR planning with associated aortic wall stress analysis to minimize adjacent aortic trauma and assist in future stent design.

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