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.

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.

scholarly journals Morphologic and Haemodynamic Changes after Stent Placement for Experimental Carotid Aneurysm

2004 ◽  
Vol 10 (1_suppl) ◽  
pp. 153-154 ◽  
Author(s):  
H. Tenjin
Keyword(s):  
Blood Flow ◽  
Digital Subtraction Angiography ◽  
Stent Placement ◽  
Carotid Arteries ◽  
Parent Artery ◽  
Digital Subtraction ◽  
Thin Slices ◽  
Before And After ◽  
Haemodynamic Changes ◽  
Plastic Resin

We investigated and compared the morphologic and haemodynamic changes between before and after stent placement when several different kinds of stents were applied to experimental aneurysms. Experimental aneurysms in eight pig carotid arteries were used. Stents were placed covering the aneurysm orifice. Five Cordis stents (coil stent), two GFXs (multilink stent), and one Multilink (tube stent) were used in this study. After stent placement, the arteries were perfused with 70% ethanol, the specimens were embedded in polyester plastic resin and thin slices were stained with hemtoxilin-eosin. Blood flow in the aneurysm was measured using digital subtraction angiography. The parent artery was stretched in multilink stent (GFX) cases, and was most markedly stretched by use of the tube stent (Multilink). Stent placement with any type of stent decreased intra-aneurysmal blood flow.

Abstract W P76: Parent Artery Curvature May Help Determine the Effectiveness of Flow Diverter Treatment

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Brando Dimapasoc ◽  
Aichi Chien
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Simulation Analysis ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Parent Artery ◽  
Flow Volume ◽  
Aneurysm Neck ◽  
Flow Reduction ◽  
Before And After

Introduction: Flow diverters (FDs) aim to treat intracranial aneurysms by altering intra-aneurysmal hemodynamics. Reports have suggested aneurysm and parent artery shape may affect flow reduction in FD-treatment. The purpose of this study is to gain insight into the way in which aneurysm shape and parent artery curvature influence the ability of FDs to redirect flow. Hypothesis: Aneurysm dome size and parent artery curvature affect FD-induced flow reduction within an aneurysm. Methods: FD models constructed based on the Pipeline Embolization Device with 35% area coverage, 30 um strand diameter, and 4 mm nominal diameter were implemented for hemodynamic simulation analysis. The flow reduction effects were tested using aneurysm models featuring different dome sizes and parent artery curvatures. Aneurysm blood flow was analyzed before and after FD stenting in regions of the aneurysm neck, body, and dome. Results: We found that aneurysms with higher parent artery curvature had increased systole flow volume entering aneurysms before and after stenting, regardless of aneurysm size, with pre-FD volume flow rates for curvatures of 20 and 30 degrees, respectively, 1.54 and 2.40 times those for 10 degree curvature. Furthermore, FD reduced flow less in aneurysms with higher curvature. For parent artery curvatures of 10, 20, and 30 degrees, overall reductions of flow volume entering the aneurysm were 91.1±0.56%, 88.2±1.2%, and 85.5±0.28%, respectively. 97.2% of models had more flow reduction at the aneurysm dome than neck. Figure 1 shows representative, post-FD flow in 10 and 30 degree parent arteries, with a greater volume flow rate in (b) depicted by denser streamlines. Aneurysm dome size was not found to have a significant effect on volume flow rate. Conclusions: We found that artery curvature may have a large influence on FD flow reduction, indicating that FD may be less effective at reducing blood flow entering aneurysms located within higher curvature arteries.

scholarly journals Risk factors for coil protrusion into the parent artery and associated thrombo-embolic events following unruptured cerebral aneurysm embolization

2015 ◽  
Vol 21 (2) ◽  
pp. 178-183 ◽  
Author(s):  
Hideaki Ishihara ◽  
Shoichiro Ishihara ◽  
Jun Niimi ◽  
Hiroaki Neki ◽  
Yoshiaki Kakehi ◽  
...  
Keyword(s):  
Risk Factors ◽  
Blood Flow ◽  
Coil Embolization ◽  
Cerebral Aneurysms ◽  
Operation Time ◽  
Vascular Reconstruction ◽  
Parent Artery ◽  
Unruptured Cerebral Aneurysm ◽  
Aneurysm Embolization ◽  
Wide Neck

Objective Advances in vascular reconstruction devices and coil technologies have made coil embolization a popular and effective strategy for treatment of relatively wide-neck cerebral aneurysms. However, coil protrusion occurs occasionally, and little is known about the frequency, the risk factors and the risk of thrombo-embolic complications. Method We assessed the frequency and the risk factors for coil protrusion in 330 unruptured aneurysm embolization cases, and examined the occurrence of cerebral infarction by diffusion-weighted magnetic resonance imaging (DW-MRI). Result Forty-four instances of coil protrusion were encountered during coil embolization (13.3% of cases), but incidence was reduced to 33 (10% of cases) by balloon press or insertion of the next coil. Coil protrusion occurred more frequently during the last phase of the procedure, and both a wide neck (large fundus to neck ratio) (OR = 1.84, P = 0.03) and an inadequately stable neck frame (OR = 5.49, P = 0.0007) increased protrusion risk. Coil protrusions did not increase the incidence of high-intensity lesions (infarcts) on DW-MRI (33.3% vs 29% of cases with no coil protrusion). However, longer operation time did increase infarct risk ( P = 0.0003). Thus, tail or loop type coil protrusion did not increase the risk of thrombo-embolic complications, if adequate blood flow was maintained. Conclusion Coil protrusion tended to occur more frequently in cases of wide-neck aneurysms with loose neck framing. Moderate and less coil protrusion carries no additional thrombo-embolic risk, if blood flow is maintained, which can be aided by additional post-operative antiplatelet therapy.

Effects of Intravascular Volume Expansion on Cerebral Blood Flow in Patients with Ruptured Cerebral Aneurysms

Neurosurgery ◽  
1987 ◽  
Vol 21 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Iwao Yamakami ◽  
Katsumi Isobe ◽  
Akira Yamaura
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Volume Expansion ◽  
Cerebral Aneurysms ◽  
Mean Value ◽  
Initial Slope ◽  
Intravascular Volume ◽  
Symptomatic Vasospasm ◽  
Arterial Blood ◽  
Before And After

Abstract To clarify the effect of intravascular volume expansion on cerebral blood flow (CBF) in patients after subarachnoid hemorrhage (SAH), we performed 55 pairs of regional CBF measurements using the xenon-133 inhalation method before and after volume expansion in 35 patients with ruptured cerebral aneurysms. CBF was calculated as the hemispheric mean value of the initial slope index. To accomplish volume expansion, we transfused 500 ml of 5% human serum albumin in half an hour. After volume expansion with albumin, the hemoglobin value decreased significantly (P < 0.005). Volume expansion did not change the mean arterial blood pressure. During the first 2 weeks after SAH, CBF decreased significantly after volume expansion (P < 0.005). During the 3rd week after SAH and subsequently to the 4th week after SAH, volume expansion produced no change in CBF. In patients with symptomatic vasospasm, CBF decreased significantly after volume expansion (P < 0.005). In patients without symptomatic vasospasm, volume expansion produced no change in CBF. The results of this study suggest that increasing the intravascular volume above normal by volume expansion does not increase CBF or reverse symptomatic vasospasm.

scholarly journals High-speed quantitative optical imaging of absolute metabolism in the rat cortex

2019 ◽  
Author(s):  
R. H. Wilson ◽  
C. Crouzet ◽  
M. Torabzadeh ◽  
A. Bazrafkan ◽  
N. Maki ◽  
...  
Keyword(s):  
Blood Flow ◽  
High Speed ◽  
Cerebral Metabolism ◽  
Flow Speed ◽  
Laser Speckle ◽  
Positron Emission ◽  
Tissue Scattering ◽  
Single Animal ◽  
Survival Studies ◽  
Zero Flow

AbstractQuantitative measures of blood flow and metabolism are essential for improved assessment of brain health and response to ischemic injury. In this report, we demonstrate a multimodal technique for measuring the cerebral metabolic rate of oxygen (CMRO2) in the rodent brain on an absolute scale (μM O2 / min). We use laser speckle imaging (LSI) at 809 nm and spatial frequency domain imaging (SFDI) at 655 nm, 730 nm, and 850 nm to obtain spatiotemporal maps of cerebral blood flow (CBF), tissue absorption (μa), and tissue scattering (μs’). Knowledge of these three values enables calculation of a characteristic blood flow speed, which in turn is input to a mathematical model with a “zero-flow” boundary condition to calculate absolute CMRO2. We apply this method to a rat model of cardiac arrest (CA) and cardiopulmonary resuscitation. With this model, the zero-flow condition occurs during entry into CA. The CMRO2 values calculated with our method are in good agreement with those measured with magnetic resonance (MR) and positron emission tomography (PET) by other groups. Our technique provides a quantitative metric of cerebral metabolism that can potentially be used for comparison between animals and longitudinal monitoring of a single animal over multiple days, to assess differences in baseline metabolism and track recovery of metabolism in survival studies following ischemia and reperfusion.

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.

scholarly journals Virtual Reality Visualization of CFD Simulated Blood Flow in Cerebral Aneurysms Treated with Flow Diverter Stents

2021 ◽  
Vol 11 (17) ◽  
pp. 8082
Author(s):  
Sima Baheri Islami ◽  
Mike Wesolowski ◽  
William Revell ◽  
Xiongbiao Chen
Keyword(s):  
Blood Flow ◽  
Virtual Reality ◽  
Flow Behavior ◽  
Cerebral Aneurysms ◽  
Point Clouds ◽  
Parent Artery ◽  
Time Varying ◽  
Head Mounted Display ◽  
Aneurysm Treatment ◽  
The Impact

Virtual reality (VR) has the potential to be a powerful tool for the visualization of simulated blood flow in cerebral aneurysms. This paper presents our study aimed at developing the VR visualization of computational fluid dynamics (CFD) simulations of cerebral aneurysms treated with flow-diverting (FD) stents. First, a spherical sidewall aneurysm located at a simplified internal carotid artery was considered for investigating the impact of stent deployment and positioning on the corresponding spatially time-varying blood flow behavior. The three-dimensional unsteady blood flow over a cardiac cycle was simulated numerically using the finite volume method, and the distributions of hemodynamic parameters inside the aneurysm sac, and on its wall, were presented with and without stent cases. Two stent positions, with and without a gap between the artery wall and stent, were considered to show the influence of correct stent position on aneurysm treatment. Second, a straightforward workflow was developed to import, process, and visualize the CFD analysis data in a VR environment by using open-source software with a high resolution. The Unity3D engine was used for displaying the processed animations in a VR environment operated on a head-mounted display (HMD). The refining process of each frame of time-varying CFD data was automated. The animated flow elements rendered in the VR environment were velocity vectors, velocity contours, streamlines, particle traces, and point clouds. CFD results showed that proper stenting facilitates thrombosis and occlusion of the aneurysm by modification of the flow patterns, which leads to lower inflow jet velocities into the aneurysm, longer turnover time, lower aneurysm-averaged kinetic energy, and lower wall shear stress. Additionally, the results indicated that a gap between the stent and the parent artery may lead to undesirable hemodynamic alterations. The VR visualization illustrated that the recognition of the potential in danger regions of aneurysms and the evaluation of the performance of FD stents in aneurysm treatment can be conducted without the need for several slices through the parent artery and aneurysm, as is required for traditional postprocessing methods. Through VR visualization, the details of the simulation results become readily available by navigating in the 3D animated flow elements using a high-degree-of-freedom headset.

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