The Effect of 3D Visualization on Optimal Design for Strut Position of Intracranial Stent

2010 ◽  
Author(s):  
Hitomi Anzai ◽  
Toshio Nakayama ◽  
Yuriko Takeshima ◽  
Makoto Ohta
Keyword(s):  
Flow Pattern ◽  
3D Visualization ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Side Wall ◽  
Flow Speed ◽  
Original Position ◽  
Parent Artery ◽  
Flow Reduction ◽  
Commercial Code

Cerebral aneurysms generally occur at arterial bifurcations and arterial curves in or near the circle of Willis. For the treatment of this disorder, stent placement has been valued as a minimal invasive therapy. The effect of stents on flow reduction in cerebral aneurysms has been examined in several computed fluid dynamics (CFD) studies, suggesting that the stent position or the strut shape may affect flow reduction. However, the position of the stent with the best effect on flow reduction is still unknown because of the flow complexity. Three-dimensional visualization may help to easily specify the inflow zone from the parent artery to the aneurysm and to find the relationship between the effective strut position and the flow pattern. However, confirmation of the ability of 3D visualization to determine the effective position of a stent has not been achieved. In this study, we simulated blood flow with several aneurysm geometries to confirm the effect of 3D visualization on determination of optimal stent position. First, flow simulation using real aneurysm geometries without a stent was performed as a “pre-stenting situation.” Meshes were generated using a commercial code (Gambit 2.3, Fluent Inc., NH). CFD was carried out using a commercial code (Fluent 6.3, Fluent Inc., NH) based on steady flow. The streamlines around an aneurysm were visualized using a 3D visualization system (EnSight Gold 8.2, Comuputational Engineering Inc., NC) in Realization Workspace (RWS) to visualize the inflow zone. Secondly, a rectangular solid as a strut model was set in the inflow zone using computer-aided design (CAD) techniques. CFD was then performed as a “post-stenting situation” under the same conditions as the pre-stenting situation using the same mesh generator and CFD code. Three-dimensional visualization showed an inflow zone in the aneurysm. A bundle of flow streamlines hit the wall of the neck of the aneurysm and entered it. The inflow zone was a narrow local part in contrast to the outflow. After setting a strut, a change of flow pattern could be observed. The flow speed and the wall shear stress (WSS) were both reduced. When the strut position was moved away from the original position, the flow speed and the WSS were not reduced. These results may suggest that 3D visualization can provide information useful for strut positioning to realize effective reduction of flow into an aneurysm, especially a side wall aneurysm.

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 Discrepancy between two-dimensional and three-dimensional digital subtraction angiography for the planning of endovascular coiling of small cerebral aneurysms <5 mm

2020 ◽  
Vol 26 (6) ◽  
pp. 733-740
Author(s):  
Te-Chang Wu ◽  
Yu-Kun Tsui ◽  
Tai-Yuan Chen ◽  
Ching-Chung Ko ◽  
Chien-Jen Lin ◽  
...  
Keyword(s):  
Digital Subtraction Angiography ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Endovascular Coiling ◽  
Parent Artery ◽  
Two Dimensional ◽  
Digital Subtraction ◽  
Rotational Angiography ◽  
Treatment Choices ◽  
The Impact

Background To investigate the discrepancy between two-dimensional digital subtraction angiography and three-dimensional rotational angiography for small (<5 mm) cerebral aneurysms and the impact on decision making among neuro-interventional experts as evaluated by online questionnaire. Materials and methods Eight small (<5 mm) ruptured aneurysms were visually identified in 16 image sets in either two-dimensional or three-dimensional format for placement in a questionnaire for 11 invited neuro-interventionalists. For each set, two questions were posed: Question 1: “Which of the following is the preferred treatment choice: simple coiling, balloon remodeling or stent assisted coiling?”; Question 2: “Is it achievable to secure the aneurysm with pure simple coiling?” The discrepancies of angio-architecture parameters and treatment choices between two-dimensional-digital subtraction angiography and three-dimensional rotational angiography were evaluated. Results In all eight cases, the neck images via three-dimensional rotational angiography were larger than two-dimensional-digital subtraction angiography with a mean difference of 0.95 mm. All eight cases analyzed with three-dimensional rotational angiography, but only one case with two-dimensional-digital subtraction angiography were classified as wide-neck aneurysms with dome-to-neck ratio < 1.5. The treatment choices based on the two-dimensional or three-dimensional information were different in 56 of 88 (63.6%) paired answers. Simple coiling was the preferred choice in 66 (75%) and 26 (29.6%) answers based on two-dimensional and three-dimensional information, respectively. Three types of angio-architecture with a narrow gap between the aneurysm sidewall and parent artery were proposed as an explanation for neck overestimation with three-dimensional rotational angiography. Conclusions Aneurysm neck overestimation with three-dimensional rotational angiography predisposed neuro-interventionalists to more complex treatment techniques. Additional two-dimensional information is crucial for endovascular treatment planning for small cerebral aneurysms.

3D CT Angiography as a Pre-Embolization Study for Embolization of Cerebral Aneurysms

1997 ◽  
Vol 3 (2_suppl) ◽  
pp. 142-148 ◽  
Author(s):  
K. Fukasaku ◽  
M. Negoro ◽  
M. Bundo ◽  
N. Kourogi ◽  
K. Yamano ◽  
...  
Keyword(s):  
Ct Angiography ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Parent Artery ◽  
3D Images ◽  
Image Guide ◽  
Laser Lithography ◽  
Real Model ◽  
Aneurysm Embolization ◽  
3D Ct Angiography

An image guide for aneurysm embolization based on three dimensional CT angiography is reported. Multiplanner reformation (MPR) can measure the neck and dome of the aneurysm accurately enough to select the first coils for aneurysms. For neck evaluation, cut model and virtual endoscope are helpful because we can observe the neck from inside of dome or parent artery. Proximal arteries are visualized by 3D images and MPR if needed. Using laser lithography, we can get a real model of aneurysm and parent artery through which we can insert microcatheters and coils. 3D CTA is a dependable modality for embolization of cerebral aneurysms.

scholarly journals Early Experience Studying Cerebral Aneurysms with Rotational and Three-Dimensional Angiography and Review of CT and MR Angiography Literature

2002 ◽  
Vol 8 (4) ◽  
pp. 377-391 ◽  
Author(s):  
C.H. Castaño-Duque ◽  
J. Ruscalleda-Nadal ◽  
M. de Juan-Delago ◽  
E. Guardia-Mas ◽  
L. San Roman-Manzanera ◽  
...  
Keyword(s):  
Intracranial Aneurysms ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Endovascular Embolization ◽  
Lower Sensitivity ◽  
Parent Artery ◽  
Philips Medical System ◽  
Multiple Series ◽  
Total Occlusion ◽  
Aneurysmal Neck

From september 2000 to september 2001, 32 consecutive patients with ruptured intracranial aneurysms were examined with rotational and 3D reconstruction angiography using an Integris V5000 Philips Medical System: 39 aneurysms were detected. After a selective cerebral artery was catheterized with a 5F or 4F-catheter, 35 ml of contrast medium was intra-arterially administered at a rate of 4 ml/s and a 180° rotational angiography was performed in eight seconds. This information was transferred to a computer (Silicon Graphics Octane) with software (Integris 3DRA, Philips Integris Systems) and a three-dimensional reconstruction was made. The information provided by Angio-3D was useful for evaluating the parent artery, aneurysmal sac, aneurysmal neck and arterial branches. It was also very useful in selecting the therapeutic method. For open surgery, this technique provides preoperative images that are useful for planning microsurgical approaches, especially in cases of large aneurysm showing complex surrounding arteries. For endovascular embolization, various anatomic characteristics of the aneurysm such as neck and sac size, shape, lobularity, parent artery and arterial branches adjacent to the aneurysmal neck must be demonstrated. This is very important to determine the best projection for embolization and to avoid multiple series. This is also essential in the choice of the first coil to create a good basket producing total occlusion. Microaneurysms are demonstrated well with this technique whereas this is difficult to do with conventional arteriography. The Angio-RM and Angio-CT literature show a lower sensitivity and specificity in comparasion with our experience with 3D IA-ROT-DSA. For this reason, we believe that 3D IA-ROTDSA is now the gold standard for patients presenting intracranial aneurysms.

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.

scholarly journals Non-Atherosclerotic Fusiform Cerebral Aneurysms

2002 ◽  
Vol 29 (1) ◽  
pp. 41-48 ◽  
Author(s):  
J. Max Findlay ◽  
Chunhai Hao ◽  
Derek Emery
Keyword(s):  
Connective Tissue ◽  
Cerebral Aneurysms ◽  
Side Wall ◽  
Endovascular Coiling ◽  
Parent Artery ◽  
Cerebral Atherosclerosis ◽  
Parent Artery Occlusion ◽  
Risk Of Rupture ◽  
Thin Walled ◽  
Proximal Occlusion

Background:Fusiform cerebral aneurysms are dilatations of the entire circumference of a segment of cerebral artery, usually considered due to atherosclerosis in adults. They are relatively thick-walled and elongated, causing neural compression or ischemia when discovered. We have noted a subset of fusiform cerebral aneurysms that vary from this common description.Patients:Out of a series of 472 intracranial aneurysms treated over 11 years, 11 patients between the ages 16 and 67 years (mean age 37) were identified who had discrete fusiform aneurysms unassociated with generalized cerebral atherosclerosis, connective tissue disorder or inflammation. Three presented with hemorrhage, six with neural compression by the aneurysm and two were discovered incidentally.Results:Nine aneurysms were located in the posterior circulation, the other two in the intracranial carotid artery. Their mean length and width were 16.3 and 11 mm, respectively. Three aneurysms contained thrombus. The eight aneurysms that were exposed surgically were partly or substantially thin-walled with normal appearing parent arteries. Eight were treated with proximal occlusion and three were circumferentially “wrapped”. Parent artery occlusion caused one death and one mild disability and the remaining patients made good recoveries (follow-up 0.5 - 10 years).Conclusions:There is a subset of cerebral aneurysms with discrete fusiform morphology, apparently unrelated to cerebral atherosclerosis or systemic connective tissue disease, thin-walled in part or whole, more common in the vertebrobasilar system, and possessing a risk of rupture. Treatments currently available include proximal occlusion or aneurysm “wrapping”, different approaches than neck-clipping or endovascular coiling of side-wall saccular cerebral aneurysms that leave the parent artery intact.

scholarly journals Three-dimensional printing of anatomically accurate, patient specific intracranial aneurysm models

2015 ◽  
Vol 8 (5) ◽  
pp. 517-520 ◽  
Author(s):  
Jeff R Anderson ◽  
Walker L Thompson ◽  
Abdulaziz K Alkattan ◽  
Orlando Diaz ◽  
Richard Klucznik ◽  
...  
Keyword(s):  
Fused Deposition Modeling ◽  
Statistical Significance ◽  
Three Dimensional ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Parent Artery ◽  
Significant Group ◽  
Fused Deposition ◽  
Deposition Modeling ◽  
3D Printed

ObjectiveTo develop and validate a method for creating realistic, patient specific replicas of cerebral aneurysms by means of fused deposition modeling.MethodsThe luminal boundaries of 10 cerebral aneurysms, together with adjacent proximal and distal sections of the parent artery, were segmented based on DSA images, and corresponding virtual three-dimensional (3D) surface reconstructions were created. From these, polylactic acid and MakerBot Flexible Filament replicas of each aneurysm were created by means of fused deposition modeling. The accuracy of the replicas was assessed by quantifying statistical significance in the variations of their inner dimensions relative to 3D DSA images. Feasibility for using these replicas as flow phantoms in combination with phase contrast MRI was demonstrated.Results3D printed aneurysm models were created for all 10 subjects. Good agreement was seen between the models and the source anatomy. Aneurysm diameter measurements of the printed models and source images correlated well (r=0.999; p<0.001), with no statistically significant group difference (p=0.4) or observed bias. The SDs of the measurements were 0.5 mm and 0.2 mm for source images and 3D models, respectively. 3D printed models could be imaged with flow via MRI.ConclusionsThe 3D printed aneurysm models presented were accurate and were able to be produced inhouse. These models can be used for previously cited applications, but their anatomical accuracy also enables their use as MRI flow phantoms for comparison with ongoing studies of computational fluid dynamics. Proof of principle imaging experiments confirm MRI flow phantom utility.

scholarly journals Complex cerebral aneurysms: intra-luminal reconstruction using Pipeline flow-diverting stent and the obliteration mechanism

2019 ◽  
Vol 33 (2) ◽  
pp. 91-97 ◽  
Author(s):  
Xianli Lv ◽  
Chuhan Jiang ◽  
Zhongxue Wu ◽  
Weijian Jiang ◽  
Guihuai Wang
Keyword(s):  
Cerebral Aneurysms ◽  
Side Wall ◽  
Intracerebral Hematoma ◽  
Parent Artery ◽  
Pipeline Flow ◽  
Aneurysm Occlusion ◽  
Occlusion Rate ◽  
Small Aneurysms ◽  
Flow Diverting Stent

Objectives Patients with complex cerebral aneurysms can now be treated intravascularly with the help of flow-diverting stents. The primary purpose of this article is to document the clinical and angiographic outcomes in 80 patients who were treated with the Pipeline flow-diverting stent (PFS; Medtronic, Dublin, Ireland) and the obliteration mechanism was discussed. Patients and methods Between October 2015 and October 2019, 80 patients with 90 complex (undefined neck, large/giant, blood blister–like, and recurrent side-wall) cerebral aneurysms treated with the PFS were retrospectively reviewed. Forty-five patients were women and 35 were men, with a mean age of 52 years. Large or giant aneurysms were defined as 10 mm or larger and small aneurysms were defined as less than 10 mm at the largest diameter measured on angiogram. Results Forty-one aneurysms (45.6%) were large or giant, 41 (45.6%) were small, four (4.4%) were recurrent side-wall aneurysms and four (4.4%) were blood blister–like aneurysms. In total, 87 PFSs were placed in 80 patients with 90 aneurysms. In six patients, coexisting proximal stenosis of parent artery was also covered with PFS without balloon angioplasty. Adjunct coils were placed in 31 aneurysms (34%). One patient died of intracerebral hematoma after thrombolysis. There was one intrastent occlusion at six-month follow-up without any symptoms. The morbidity and the mortality rate is 0% and 1.3% (95% confidence interval (CI), 0%–3.7%). Control angiography was available in 74 (92.5%) patients with 83 aneurysms, and the aneurysm occlusion rate was 98.8% (95% CI, 96.5%–100%) in 6 to 12 months. Conclusion For wide-necked saccular, large/giant, blood blister–like aneurysms and recurrent side-wall aneurysms, PFS is a valid and safe treatment option.

A Computational Modelling for Hemodynamic Conditions Following Flow-Diverting Treatment in Cerebral Aneurysms

2018 ◽  
Author(s):  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
Average Velocity ◽  
Physiological State ◽  
Cerebral Aneurysms ◽  
Side Wall ◽  
Flow Diverter ◽  
Geometrical Parameters ◽  
Parent Artery ◽  
Flow Diverter Stent ◽  
Structure Of Flow ◽  
Flow Diverters

Cerebral aneurysms are abnormal dilations of blood vessels within the skull that, in some cases, may rupture and bleed. The rupture of an aneurysm can cause significant bleeding into or around the brain (a stroke). Flow diverters are specially designed low porosity stents that are deployed into the parent artery to cover the neck of the aneurysm. The dense mesh-like structure of flow diverters aims at redirecting flow from the aneurysm to the parent artery and vice versa, resulting in flow stasis in the aneurysm and promoting thrombus formation conditions. The thrombosed aneurysm is then resorbed by the body’s wound healing mechanisms-the end result of which is a remodeled vessel returned to its normal physiological state. Most previous studies have been focused on correlating the hemodynamic conditions with the outcome of the flow diverters. On the other hand, the effects of the location of the stents have not been addressed. In this study, a numerical simulation of an idealized side wall aneurysm model is used to predict the hemodynamic conditions for different flow diverter stent locations. The CFD model of the aneurysm is developed based on data from the literature and the geometrical parameters are set according to the test data. Pulsatile boundary conditions are chosen according to the normal physiological conditions. The entire stent geometry is used to model the effect of the stent on the flow characteristics. The hemodynamic conditions in the aneurysm corresponding to different stent locations are compared. The results show that the average velocity and vorticity are significantly different depending on different stent locations. Marked reduction in average velocity, average vorticity, and mean wall shear stress within the aneurysm sac have been observed even in malposition cases. The results of this study can be further used to guide the deployment of the flow diverter stent in clinical application.

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