Development of Stent Strut Pattern for Cerebral Aneurysm

2010 ◽  
Author(s):  
Toshio Nakayama ◽  
Shinkyu Jeong ◽  
Srinivas Karkenahalli ◽  
Makoto Ohta
Keyword(s):  
Blood Flow ◽  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Optimization Method ◽  
Flow Speed ◽  
Parent Artery ◽  
Stent Strut ◽  
Computational Fluid Dynamics Cfd ◽  
Commercial Solver ◽  
Volume Method

Background and purpose: Stent implantation (stenting) in intracranial arteries is termed as endovascular treatment. The number of such cases has been increasing worldwide because the surgical damage resulting from stenting seem to be less than that of other treatments. The role of stenting for cerebral aneurysms is to reduce the blood flow speed in cerebral aneurysms. We have developed a computational fluid dynamics (CFD) system using a realistic stent and blood vessel and have studied the effect of the stent. Results of our study showed the stent strut pattern and stenting position to be very effective for reducing the blood flow speed in cerebral aneurysms. We have in describe the designing method used to design the stent strut pattern which reduces both the blood flow speed and the wall shear stress (WSS). Methods: An idealized aneurysm, a parent artery, and various stent shapes were used. The shape of the parent artery was a straight pipe and the aneurysm was a sphere. The stent was implanted in the neck of the aneurysm. The porosity remained of 80%, and the width of the stent strut ranged from 90 to 160[μm]. The stent strut height was fixed at a constant 150 [μm]. For the constructed shape data, a tetrahedron numerical mesh was generated. Calculation using the finite volume method was performed by a commercial solver. The optimization method was applied to the CFD results, and the stent strut patterns that reduced the blood flow speed and the WSS most were determined. Conclusion: The development method of stent strut pattern was proposed. Various stent strut patterns to reduce blood flow speed and WSS in/on cerebral aneurysm were tested. The stent strut pattern that reduced the blood flow speed and that reduced the WSS were determined. In the future works, the number of CFD cases should be increased and the optimal stent strut pattern determined.

Classification of Blood Flow in Cerebral Aneurysm Considering the Parent Artery Curves

2013 ◽  
Author(s):  
Toshio Nakayama ◽  
Shin-ichiro Sugiyama ◽  
Makoto Ohta
Keyword(s):  
Blood Flow ◽  
Flow Pattern ◽  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Flow Simulation ◽  
Flow Speed ◽  
Parent Artery ◽  
Blood Flow Pattern ◽  
Stent Strut

Background and purpose: Recently, the number of endovascular treatments has increased worldwide because of advances in minimally invasive surgery. We considered the effect of reduced flow due to stent implantation and proposed the design of stent strut pattern from the viewpoint of fluid dynamics. We developed an optimized stent strut pattern using a computational fluid dynamics (CFD) system. A classification of cerebral aneurysms was proposed using the aspect ratio (AR) and the stent strut pattern was optimized. The results of optimal stent strut pattern for reduced blood flow speed and wall shear stress were different, and the influence of the AR values was small because there was no dependence on relationship between blood flow and the AR values due to the use of a straight pipe in the parent artery. The classification of blood flow pattern in a cerebral aneurysm must consider the parent artery curves. In this study, we investigated the relationship between the blood flow pattern in cerebral aneurysms and parent artery curves using CFD. Methods: To investigate the influence of blood flow based on the parent artery curve, the parent artery shape was constructed as follows. Patient-specific parent artery shape with a cerebral aneurysm was reconstructed using OsiriX. Center line was extracted using a vascular modeling tool kit. The parent artery shape was reconstructed based on this center line using CAD. The diameter of the parent artery was 4 mm. The cerebral aneurysm shape was a combination of a straight pipe and a half sphere, and the AR value was fixed at 1.0. The cerebral aneurysm position varied from the original position to a 180° rotated position. Tetrahedral numerical mesh was generated with a commercial mesh generator (ICEM CFD 14.0; Ansys Inc.) for the CFD analysis. The numerical blood flow simulation was performed on a supercomputer using the commercial ANSYS FLUENT 6.3 software package and the finite volume method, and a steady flow simulation was performed. Boundary conditions were set for velocity at the inlet, pressure at the outlet, no-slip parent artery, and stent surface. Reynolds numbers at the inlet determined from the mean blood flow speed were 240 and 600. Results and discussion: In this study, we revealed the blood flow pattern in some cerebral aneurysms using CFD. The pattern in a cerebral aneurysm was influenced by the aneurysm direction and parent artery curves. The blood flow pattern in a neck cerebral aneurysm was classified into two types.

Cinematic Angiography for Measurements of Blood Flow in Cerebral Aneurysms With Stents

2007 ◽  
Author(s):  
Makoto Ohta ◽  
Naoko Fujimura ◽  
Luca Augsburger ◽  
Hasan Yilmaz ◽  
Daniel A. Ru¨fenacht
Keyword(s):  
Blood Flow ◽  
High Speed ◽  
Cerebral Aneurysms ◽  
Flow Speed ◽  
Circulation System ◽  
Parent Artery ◽  
Vortex Center ◽  
System A ◽  
Before And After ◽  
Movement Distance

Background and Purpose: The assessment of blood flow speed by imaging modalities is important for endovascular treatments, such as stent implantation, of cerebral aneurysms. The subtracted vortex centers path line method (SVC method) is one of the ways of determining flow speed quantitatively using the image sequence. And a cinematic angiography (CA) is a high speed image acquisition system using X-ray and contrast media integrated in Digital Subtraction Angiography (DSA) for endovascular therapy. The combination of SVC and CA may useful for determining the blood flow speed during the operation using DSA. In this study, we applied this combination to analyze hemodynamic changes before and after stenting. Methods: A transparent tubular model was constructed of silicone which included an aneurysm 10 mm in diameter and having a 5 mm neck on a straight parent artery with a diameter of 3.5 mm. The model was integrated into a pulsatile circulation system. A double layer stent was placed in the parent artery on the aneurysm. By CA, successive images at 25 frames per second with injection of contrast were obtained. Results and conclusion: Rotating vortexes of contrast, which advanced along the wall of the aneurysm, were observed in successive images of the aneurysm cavity. The movement distance of the vortex center was measured and the results show that the vortex speed decrease after stenting. This indicates the possibility of applying the SVC method to medical imaging equipment for analysis of the flow in aneurysms containing stent.

scholarly journals Computed Tomography Image under Optimized Iterative Reconstruction Algorithm to Analyze the Characteristics of Blood Flow Field in Cerebral Aneurysm before and after Stent Implantation

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Kunyang Bao ◽  
Chao Liu ◽  
Jin Li ◽  
Xiang Liu ◽  
Wenzhang Luo ◽  
...  
Keyword(s):  
Blood Flow ◽  
Flow Field ◽  
Cerebral Aneurysm ◽  
Iterative Reconstruction ◽  
Stent Implantation ◽  
Cerebral Aneurysms ◽  
Reconstruction Algorithm ◽  
Ct Images ◽  
Iterative Reconstruction Algorithm ◽  
The Difference

In order to analyze the change characteristics of blood flow field in cerebral aneurysms before and after stent implantation, this study first constructed an optimized iterative reconstruction algorithm to reconstruct CT images of patients with cerebral aneurysms and used it to solve the problem of image sharpness. In addition, backprojection image reconstruction algorithm and Fourier transform analytic method were introduced. According to the CT images of cerebral arteries of patients, the lesions were presented in a three-dimensional and visual way through the reconstructed three-dimensional images, thus achieving the effects of simulation and simulation. The results showed that the sensitivity, specificity, and accuracy of the optimized iterative reconstruction algorithm were 90.78%, 83.27%, and 94.82%, which were significantly higher than those of the backprojection image reconstruction algorithm and Fourier transform analysis method, and the difference was statistically significant ( P < 0.05 ). Before operation, the blood flow velocity in the neck of aneurysm was 7.35 × 10−2 m/s, the exit velocity was 1.51 × 10−1 m/s, and the maximum velocity appeared in the upstream part of the exit. After passing through the aneurysm, the blood flow velocity began to decrease gradually, forming a vortex at the top of the tumor. After stent implantation, the neck and outlet velocities of cerebral aneurysm were 9.352 × 10−2 m/s and 1.897 × 10−2 m/s, respectively. The velocity of blood flow decreased after entering the aneurysm, and there was no vortex at the top of the aneurysm. Among the outlet velocities of arterial blood vessels, the velocity before stent implantation was significantly lower than that after stent implantation, and the difference was statistically significant ( P < 0.05 ). Compared with prestent, the shear force distribution on the wall of cerebral aneurysm showed a significant decrease, and the difference was statistically significant ( P < 0.05 ). To sum up, pelvic floor ultrasound based on hybrid iterative reconstruction algorithm has high accuracy in diagnosing the changes of blood flow field in cerebral aneurysms. The application of CT images in the diagnosis of cerebral aneurysms can objectively provide imaging data for clinical practice and has high application value.

Evaluation of Cerebral Aneurysm Stent Performance in a Subject-Specific Computational Model

2010 ◽  
Author(s):  
Timothy J. Gundert ◽  
John F. LaDisa
Keyword(s):  
United States ◽  
Blood Flow ◽  
Computational Model ◽  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
The United States ◽  
Flow Stagnation ◽  
Subject Specific ◽  
Endovascular Devices ◽  
Saccular Aneurysms

Rupture of cerebral aneurysms is the second leading cause of stroke in the United States [1]. Altered hemodynamics is thought to play a role in the progression and subsequent rupture of aneurysms. Blood flow into an aneurysm can be occluded by surgically clipping the aneurysm or using endovascular devices, such as stents or coils. In saccular aneurysms, coiling alone may be a sufficient method of inducing flow stagnation in the aneurysm, causing thrombosis and preventing rupture. When treating wide-necked aneurysms, stenting is often used in conjunction with coiling to prevent the migration of coils. Many investigators have studied the ability of a stent-only treatment to favorably alter flow in aneurysms [2, 3].

scholarly journals Lyophilizing thrombin powder-based treatment for hemostasis during coil embolization of ruptured cerebral aneurysm: Two case reports

2019 ◽  
Vol 25 (4) ◽  
pp. 454-459
Author(s):  
Changchun Jiang ◽  
Wei Wang ◽  
Baojun Wang ◽  
Yuechun Li ◽  
Guorong Liu ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
Coil Embolization ◽  
Case Reports ◽  
Balloon Catheter ◽  
Treatment Strategies ◽  
Cerebral Aneurysms ◽  
Interventional Therapy ◽  
Parent Artery ◽  
Clinical Practices ◽  
Detachable Coils

Background Rupture of cerebral aneurysm is an inevitable complication during embolization, followed by subsequent acute subarachnoid hemorrhage or intracranial hematoma, and results in the aggravation of a patient’s condition. In particular, for patients who have had a ruptured aneurysm, urgent treatment strategies are required during operation. The most common hemostatic methods seen in clinical practices are as follows: after lowering the blood pressure, we continue to embolize the aneurysms with detachable coils as soon as possible or inject with Glubran/Onyx embolization liquids, as well as use a balloon catheter to temporarily block the blood supply. If the conditions are permissible, a balloon guiding catheter may even be used to restrict the proximal blood flow. At times, due to limitations of these methods, neurosurgeons are requested to perform craniotomy to treat the hemostasis. However, the delayed transition often leads to rapid deterioration of the patient’s condition and even death due to cerebral hernia. Case description We herein presented two cases of ruptured cerebral aneurysms to provide an alternative method for hemostasis and to save the lives of patients as much as possible. In an extremely urgent situation (conventional treatment is ineffective), we successfully saved the patient’s life by injecting lyophilizing thrombin powder (LTP) solution into the aneurysmal sac and the parent artery through a microcatheter. Conclusions To our knowledge, this is the first report of successful hemostasis during coil embolization of ruptured cerebral aneurysm with LTP. Further prospective studies are needed to confirm the safety and efficacy of LTP in cerebrovascular interventional therapy.

scholarly journals A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Jürgen Endres ◽  
Markus Kowarschik ◽  
Thomas Redel ◽  
Puneet Sharma ◽  
Viorel Mihalef ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Risk Of Rupture ◽  
Computational Fluid Dynamics Cfd ◽  
Subsequent Comparison

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

CFD Challenge: Solutions Using the Commercial Solver Fluent and the Open-Source Solver OpenFOAM

2012 ◽  
Author(s):  
P. Berg ◽  
G. Janiga ◽  
D. Thévenin
Keyword(s):  
Blood Flow ◽  
Cerebral Aneurysms ◽  
Flow Simulation ◽  
Patient Specific ◽  
Post Processing ◽  
Close Collaboration ◽  
Blood Flow Simulation ◽  
Unsteady Blood Flow ◽  
Commercial Solver ◽  
Considerable Experience

During the last decade, the research group in Magdeburg investigated the hemodynamics in cerebral aneurysms in close collaboration with experts from the fields of visualization and neuroradiology. Thanks to this, a considerable experience has been collected concerning unsteady blood flow simulation and analyses, involving a steadily increasing number of patient-specific aneurysms. Intermediate results have been presented at several VISC challenges. The simulations regarding this CFD Challenge as well as the post-processing have been carried out by the doctoral student Philipp Berg.

scholarly journals Influence of different computational approaches for stent deployment on cerebral aneurysm haemodynamics

2011 ◽  
Vol 1 (3) ◽  
pp. 338-348 ◽  
Author(s):  
Annarita Bernardini ◽  
Ignacio Larrabide ◽  
Hernán G. Morales ◽  
Giancarlo Pennati ◽  
Lorenza Petrini ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Cfd Analysis ◽  
Clinical Workflow ◽  
Stent Deployment ◽  
Cerebral Vessel ◽  
Virtual Tools ◽  
Computational Fluid Dynamics Cfd ◽  
Vessel Material ◽  
Set Up

Cerebral aneurysms are abnormal focal dilatations of artery walls. The interest in virtual tools to help clinicians to value the effectiveness of different procedures for cerebral aneurysm treatment is constantly growing. This study is focused on the analysis of the influence of different stent deployment approaches on intra-aneurysmal haemodynamics using computational fluid dynamics (CFD). A self-expanding stent was deployed in an idealized aneurysmatic cerebral vessel in two initial positions. Different cases characterized by a progression of simplifications on stent modelling (geometry and material) and vessel material properties were set up, using finite element and fast virtual stenting methods. Then, CFD analysis was performed for untreated and stented vessels. Haemodynamic parameters were analysed qualitatively and quantitatively, comparing the cases and the two initial positions. All the cases predicted a reduction of average wall shear stress and average velocity of almost 50 per cent after stent deployment for both initial positions. Results highlighted that, although some differences in calculated parameters existed across the cases based on the modelling simplifications, all the approaches described the most important effects on intra-aneurysmal haemodynamics. Hence, simpler and faster modelling approaches could be included in clinical workflow and, despite the adopted simplifications, support clinicians in the treatment planning.

Abstract 1122‐000063: Postoperative Recanalization Factors of Coil Embolization for Cerebral Aneurysms with Comparable Volume Embolization Ratio

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Hayato Uchikawa ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Yuya Uchiyama ◽  
Yuma Yamanaka ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Aneurysm ◽  
High Velocity ◽  
Coil Embolization ◽  
Cerebral Aneurysms ◽  
Mean Value ◽  
Morphological Parameters ◽  
Hemodynamic Parameters ◽  
Concentrated Flow ◽  
Coil Shape

Introduction : Volume embolization ratio (VER) has been reported to be involved in postoperative recanalization of coil embolization. However, despite comparable VER, some cases remained stable, and the others showed recanalization. Hemodynamic and morphological factors, as described in previous studies, may also influence recanalization in addition to VER. In this study, we focused on cerebral aneurysms treated by coil embolization with comparable VER. Blood flow analysis using computational fluid dynamics (CFD) and geometrical measurements were performed to investigate the recanalization factors. Methods : We focused on the aneurysms that underwent coil embolization with 15–20% VER. The criteria for the case selection were that the size of the aneurysms was 5–10 mm and that the aneurysm was treated by only coil (i.e., the stent‐assisted cases were excluded). Aneurysms that recanalized after coil embolization and underwent additional coil deployment were defined as “recanalized”, and aneurysms that remained stable after coil embolization without coil compaction were defined as “stable”. Finally, we selected 7 recanalized cases (ICA: 1, MCA: 3, ACA: 3) and 18 stable cases (ICA: 6, MCA: 3, ACA: 9). CFD analysis and morphometry were performed on the vessel geometry after coil embolization. The coil shape was modeled by the virtual coil technique. We calculated three morphological parameters and 34 hemodynamic parameters, then we compared them between the recanalized and stable cases using the Mann‐Whitney U test to identify recanalization factors. In addition, we reconstructed the coil shape from medical images and compared its structure and flow characters for stable and recanalized cases. Results : The average VER for the cases analyzed in this study were 16.7% for recanalized cases and 17.7% for stable cases. As hemodynamic parameters, the spatially averaged velocity normal to the neck plane into the cerebral aneurysm ( NV neck ), and the ratio of the area where blood flows into the cerebral aneurysm after the coil embolization to the area of the neck surface (inflow area ratio: IAR) showed significant difference. Although the hemodynamic parameters were significantly different, morphological parameters did not show statistically significance. In the recanalized case, NV neck tended to be higher (mean value, recanalized: 0.931, stable: 0.822, P < 0.05), and IAR tended to be lower (mean value, recanalized: 0.319, stable: 0.408, P < 0.01). The high NV neck and low IAR indicate that the aneurysm had concentrated flow with a high velocity at the neck surface. There was the concentrated blood flow with the high velocity that collided with the modeled coil in a CFD result for the recanalized case. The area where the blood flow impinged on the modeled coil coincided with the compacted coil region reconstructed from medical images. Therefore, a large force on the coil indicated by these hemodynamic parameters may cause the postoperative recanalization. Conclusions : Even with the same level of VER, there was a possibility of recanalization in aneurysms with a high velocity and concentrated flow into the aneurysm. It is necessary to consider not only VER but also hemodynamic factors to investigate recanalization factors after the coil embolization.

Mechanism of Cerebral Aneurysm Bruits: Resonance of Parent Artery and Aneurysm

2008 ◽  
Author(s):  
L.-D. Jou ◽  
H. Morsi ◽  
M. E. Mawad
Keyword(s):  
Carotid Artery ◽  
Internal Carotid Artery ◽  
Healthy Subject ◽  
Cerebral Aneurysm ◽  
Internal Carotid ◽  
Cerebral Aneurysms ◽  
Parent Artery ◽  
Electronic Stethoscope

Cerebral aneurysms have distinct sounds that peak at a frequency between 260–660Hz, very different from the spectrum without aneurysms [1]. While this phenomenon has been known for years, the exact cause of bruits is not known. Figure 1 shows the spectrums of sounds from a healthy subject and a 65-year-old patient with a 16mm aneurysm at the paraclinoid segment of the internal carotid artery using a digital electronic stethoscope. The healthy subject has a peak at 96Hz, and the spectrum for the aneurysm patient peaks at 403 Hz.

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