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Byoun HS, Lim JW, Han MH, Jeong EO, Koh HS, Kwon HJ. Coil embolization of the middle cerebral artery bifurcation aneurysms: Feasibility and durability. J Clin Neurosci 2024; 126:294-306. [PMID: 39002303 DOI: 10.1016/j.jocn.2024.06.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/28/2024] [Accepted: 06/18/2024] [Indexed: 07/15/2024]
Abstract
OBJECTIVE To evaluate the feasibility and durability of coil embolization for MCAB aneurysms by analyzing clinical and radiological results. METHODS From January of 2008 to June of 2018, we treated a total of 1785 aneurysms using coil embolization. The aneurysms were treated by both coiling and stent-assisted coiling. Among these cases, 223 MCAB aneurysms were analyzed retrospectively. Clinical and radiological assessments were conducted at admission, after treatment, at discharge, and at last clinical follow-up. RESULTS Coil embolization was performed on 223 MCAB aneurysms in 217 patients. Peri-procedural ischemic, hemorrhagic, and other complications within 30 days after coil embolization occurred at rates of 8.0 %, 8.0 %, and 2.0 %, respectively, in the ruptured group and at 2.9 %, 1.2 %, and 0 %, respectively, in the unruptured group. The overall morbidity and mortality rates associated with complications were 2.3 % and 2.0 %. The cumulative major recurrence rates were 5.1 % at 12 months, 7.1 % at 18 months, and 11.9 % at three years after coil embolization. The mean follow-up period was 33.27 ± 25.48 months. Independent risk factors for major recurrence after coil embolization for MCAB aneurysms were a ruptured aneurysm, initial incomplete occlusion, the aneurysm size, and the neck size. CONCLUSION Coil embolization is a good alternative treatment option for MCAB aneurysms compared to surgical clipping. Considering the risk factors for major recurrence, the follow-up angiography should continue up to three years after coil embolization.
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Affiliation(s)
- Hyoung Soo Byoun
- Department of Neurosurgery, Chungnam National University Sejong Hospital, Sejong-si, South Korea
| | - Jeong-Wook Lim
- Department of Neurosurgery, Chungnam National University Sejong Hospital, Sejong-si, South Korea
| | - Myung-Hoon Han
- Department of Neurosurgery, Hanyang University Guri Hospital, Gyeonggi-do, South Korea
| | - Eun-Oh Jeong
- Department of Neurosurgery, Chungnam National University Hospital and School of Medicine, Daejeon, South Korea
| | - Hyeon-Song Koh
- Department of Neurosurgery, Chungnam National University Hospital and School of Medicine, Daejeon, South Korea
| | - Hyon-Jo Kwon
- Department of Neurosurgery, Chungnam National University Hospital and School of Medicine, Daejeon, South Korea.
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2
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Safety of coil embolisation in small (smaller than 5 mm) unruptured intracranial aneurysms: A retrospective multicentre analysis. INTERDISCIPLINARY NEUROSURGERY 2023. [DOI: 10.1016/j.inat.2022.101678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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3
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Bisighini B, Di Giovanni P, Scerrati A, Trovalusci F, Vesco S. Fabrication of Compliant and Transparent Hollow Cerebral Vascular Phantoms for In Vitro Studies Using 3D Printing and Spin-Dip Coating. MATERIALS (BASEL, SWITZERLAND) 2022; 16:166. [PMID: 36614505 PMCID: PMC9821401 DOI: 10.3390/ma16010166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/12/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
Endovascular surgery through flow diverters and coils is increasingly used for the minimally invasive treatment of intracranial aneurysms. To study the effectiveness of these devices, in vitro tests are performed in which synthetic vascular phantoms are typically used to reproduce in vivo conditions. In this paper, we propose a manufacturing process to obtain compliant and transparent hollow vessel replicas to assess the mechanical behaviour of endovascular devices and perform flow measurements. The vessel models were obtained in three main steps. First, a mould was 3D-printed in a water-soluble material; two techniques, fusion deposition modelling and stereolithography, were compared for this purpose. Then, the mould was covered with a thin layer of silicone through spin-dip coating, and finally, when the silicone layer solidified, it was dissolved in a hot water bath. The final models were tested in terms of the quality of the final results, the mechanical properties of the silicone, thickness uniformity, and transparency properties. The proposed approach makes it possible to produce models of different sizes and complexity whose transparency and mechanical properties are suitable for in vitro experiments. Its applicability is demonstrated through idealised and patient-specific cases.
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Affiliation(s)
- Beatrice Bisighini
- Mines Saint-Etienne, Université Lyon, Université Jean Monnet, Etablissement Français du Sang, INSERM, U1059 Sainbiose, Centre CIS, F-42023 Saint-Etienne, France
- Department of Enterprise Engineering, University Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
- Predisurge, 10 Rue Marius Patinaud, Grande Usine Creative 2, 42000 Saint-Etienne, France
| | | | - Alba Scerrati
- Department of Translational Medicine, University of Ferrara, Via Luigi Borsari 46, 44121 Ferrara, Italy
| | - Federica Trovalusci
- Department of Enterprise Engineering, University Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
| | - Silvia Vesco
- Department of Enterprise Engineering, University Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
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4
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Paz C, Suárez E, Cabarcos A, Pinto SIS. FSI modeling on the effect of artery-aneurysm thickness and coil embolization in patient cases. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2021; 206:106148. [PMID: 33992899 DOI: 10.1016/j.cmpb.2021.106148] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 04/26/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND AND OBJECTIVE The attainment of a methodology to simulate the hemodynamic in patient-specific cerebral vessels with aneurysms is still a challenge. The novelty of this work is focused on the effect of coil embolization in a realistic cerebral aneurysm, according to the vessel wall thickness and aneurysm thickness, through transient FSI simulations. METHODS The quality of the mesh for simulations was checked with a specific mesh convergence study; and the numerical methodology was validated using numerical research data of the literature. The model was implemented in ANSYS® software. The total deformation and equivalent stress evolution in the studied cases, before and after coil embolization, were compared. More than 20 different models were employed due to different arterial wall thickness and aneurysm wall thickness combinations. RESULTS The obtained results have showed that deformation and stress values are highly influenced with the sac thickness. The thinner sac aneurysm thickness is, the greater deformation and stress are. The results after coil embolization process have highlighted that considering typical values of arterial wall thickness and aneurysm thickness 0.3 mm and 0.15 mm respectively, a deformation reduction around 50% and a stress reduction around 70% can be achieved. CONCLUSIONS The proposed methodology is a step forward in the personalized medicine, quantifying the aneurysm rupture risk reduction, and helping the medical team in the preoperative planning, or to deciding the optimal treatment.
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Affiliation(s)
- C Paz
- CINTECX, University of Vigo, Campus Universitario Lagoas-Marcosende, Vigo 36310, España.
| | - E Suárez
- CINTECX, University of Vigo, Campus Universitario Lagoas-Marcosende, Vigo 36310, España.
| | - A Cabarcos
- CINTECX, University of Vigo, Campus Universitario Lagoas-Marcosende, Vigo 36310, España.
| | - S I S Pinto
- Engineering Faculty of University of Porto, Institute of Science and Innovation in Mechanical and Industrial Engineering (LAETA-INEGI), Rua Dr. Roberto Frias, Porto 4200-465, Portugal.
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5
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Wan H, Lu G, Huang L, Ge L, Jiang Y, Li G, Leng X, Xiang J, Zhang X. Hemodynamic Effect of the Last Finishing Coils in Packing the Aneurysm Neck. Front Neurol 2020; 11:598412. [PMID: 33329354 PMCID: PMC7714910 DOI: 10.3389/fneur.2020.598412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 10/15/2020] [Indexed: 11/13/2022] Open
Abstract
Background: Using the finishing coils to densely pack the aneurysm neck is necessary. However, the exact hemodynamic effect of finishing coils in packing the aneurysm neck is unknown. Objective: To evaluate the hemodynamic characteristics of finishing coils to densely pack the aneurysm neck, using finite element method simulation. Methods: A computational study was performed based on a 44-year-old female patient with an unruptured wide-necked carotid-ophthalmic artery aneurysm treated with low-profile visualized intraluminal support stent-assisted coil embolization. Four computational fluid dynamics models including pre-treatment, post-stenting, common stent-assisted coil embolization (SACE), and common SACE with finishing coils were evaluated qualitatively and quantitatively. Results: Compared with the baseline of pretreatment model (100%), sac-averaged velocity in post-stenting, common SACE, and common SACE with finishing coil models decreased to 95.68%, 24.38%, and 13.20%, respectively; high flow volume (>0.1 m/s) around the aneurysm neck decreased to 92.19%, 9.59%, and 5.57%, respectively; and mean wall shear stress increased or decreased to 107%, 25.94%, and 23.89%, respectively. Conclusion: Finishing coils to densely pack the aneurysm neck can generate favorable hemodynamic modifications, which may decrease the recurrence.
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Affiliation(s)
- Hailin Wan
- Huashan Hospital, Fudan University, Shanghai, China
| | - Gang Lu
- Huashan Hospital, Fudan University, Shanghai, China
| | - Lei Huang
- Huashan Hospital, Fudan University, Shanghai, China
| | - Liang Ge
- Huashan Hospital, Fudan University, Shanghai, China
| | - Yeqing Jiang
- Huashan Hospital, Fudan University, Shanghai, China
| | - Gaohui Li
- ArteryFlow Technology Co., Ltd, Hangzhou, China
| | | | | | - Xiaolong Zhang
- Huashan Hospital, Fudan University, Shanghai, China
- *Correspondence: Xiaolong Zhang
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6
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Ho WH, Tshimanga IJ, Ngoepe MN, Jermy MC, Geoghegan PH. Evaluation of a Desktop 3D Printed Rigid Refractive-Indexed-Matched Flow Phantom for PIV Measurements on Cerebral Aneurysms. Cardiovasc Eng Technol 2019; 11:14-23. [PMID: 31820351 PMCID: PMC7002330 DOI: 10.1007/s13239-019-00444-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 11/20/2019] [Indexed: 12/24/2022]
Abstract
PURPOSE Fabrication of a suitable flow model or phantom is critical to the study of biomedical fluid dynamics using optical flow visualization and measurement methods. The main difficulties arise from the optical properties of the model material, accuracy of the geometry and ease of fabrication. METHODS Conventionally an investment casting method has been used, but recently advancements in additive manufacturing techniques such as 3D printing have allowed the flow model to be printed directly with minimal post-processing steps. This study presents results of an investigation into the feasibility of fabrication of such models suitable for particle image velocimetry (PIV) using a common 3D printing Stereolithography process and photopolymer resin. RESULTS An idealised geometry of a cerebral aneurysm was printed to demonstrate its applicability for PIV experimentation. The material was shown to have a refractive index of 1.51, which can be refractive matched with a mixture of de-ionised water with ammonium thiocyanate (NH4SCN). The images were of a quality that after applying common PIV pre-processing techniques and a PIV cross-correlation algorithm, the results produced were consistent within the aneurysm when compared to previous studies. CONCLUSIONS This study presents an alternative low-cost option for 3D printing of a flow phantom suitable for flow visualization simulations. The use of 3D printed flow phantoms reduces the complexity, time and effort required compared to conventional investment casting methods by removing the necessity of a multi-part process required with investment casting techniques.
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Affiliation(s)
- W H Ho
- Department of Mechanical and Industrial Engineering, University of South Africa, Johannesburg, South Africa.,School of Mechanical Aerospace and Industrial Engineering, University of the Witwatersrand, Johannesburg, South Africa
| | - I J Tshimanga
- Department of Mechanical and Industrial Engineering, University of South Africa, Johannesburg, South Africa
| | - M N Ngoepe
- Department of Mechanical Engineering, University of Cape Town, Cape Town, South Africa
| | - M C Jermy
- Department of Mechanical Engineering, University of Canterbury, Christchurch, New Zealand
| | - P H Geoghegan
- Department of Mechanical and Industrial Engineering, University of South Africa, Johannesburg, South Africa. .,Biomedical Engineering, School of Life and Health Sciences, Aston University, Birmingham, England.
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7
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Zhao R, Liu J, McComas S, Guo J, Girdhar G. In-vitro pliability assessment of embolization coils for intracranial aneurysm treatment. J Neurol Sci 2019; 406:116432. [PMID: 31629992 DOI: 10.1016/j.jns.2019.116432] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 08/20/2019] [Accepted: 08/21/2019] [Indexed: 10/26/2022]
Abstract
BACKGROUND Embolization coils have routinely been used to treat intracranial aneurysms via an endovascular approach. Soft coils are typically viewed as the best design for filling and finishing the aneurysms to achieve a higher packing density and are hypothesized to exert a lower force against the aneurysm wall during deployment. We report here an in vitro pliability test method to assess clinically relevant coil softness and compare these metrics for two commercially available framing and finishing coil products. METHODS A force measurement sensor was affixed onto a side-wall synthetic aneurysm model to continuously measure forces on the aneurysm wall during coil deployment at a fixed delivery rate. A quantitative overall energy metric (average work number or AWN) was calculated from the force-displacement graph representing coil delivery into the aneurysm. Two groups of coils were evaluated: (a) finish coil group (N = 20 ea.): Axium™ Prime Extra Soft coil (ES) and Target™ 360 Nano coil (Nano), and (b) frame coil group (N = 20 ea.): Axium™ Prime FC coil (FC) and Target™ 360 Standard coil (Standard). RESULTS (a) In the finish coil group, AWN was measured as: ES (0.53 ± 0.09 gf-cm) and Nano (0.99 ± 0.21 gf-cm). (b) In the frame coil group, AWN was measured as FC (2.54 ± 0.53 gf-cm) and Standard (4.48 ± 0.52 gf-cm). In both groups, Axium Prime coils had statistically lower measures of AWN and therefore higher pliability compared to Target coils (p < .001). CONCLUSIONS The in-vitro pliability test method offers quantitative metrics to assess coil softness during deployment in a clinically relevant aneurysm model.
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Affiliation(s)
- Rui Zhao
- Department of Neurosurgery, Changhai Hospital, Shanghai 200433, China
| | - Jianmin Liu
- Department of Neurosurgery, Changhai Hospital, Shanghai 200433, China
| | - Steven McComas
- Medtronic PLC, 9775 Toledo Way, Irvine, CA 92618, United States
| | - Jenny Guo
- Medtronic PLC, 9775 Toledo Way, Irvine, CA 92618, United States
| | - Gaurav Girdhar
- Medtronic PLC, 9775 Toledo Way, Irvine, CA 92618, United States.
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8
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Kurşun B, Uğur L, Keskin G. Hemodynamic effect of bypass geometry on intracranial aneurysm: A numerical investigation. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2018; 158:31-40. [PMID: 29544788 DOI: 10.1016/j.cmpb.2018.02.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 12/28/2017] [Accepted: 02/02/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND AND OBJECTIVE Hemodynamic analyzes are used in the clinical investigation and treatment of cardiovascular diseases. In the present study, the effect of bypass geometry on intracranial aneurysm hemodynamics was investigated numerically. Pressure, wall shear stress (WSS) and velocity distribution causing the aneurysm to grow and rupture were investigated and the best conditions were tried to be determined in case of bypassing between basilar (BA) and left/right posterior arteries (LPCA/RPCA) for different values of parameters. METHODS The finite volume method was used for numerical solutions and calculations were performed with the ANSYS-Fluent software. The SIMPLE algorithm was used to solve the discretized conservation equations. Second Order Upwind method was preferred for finding intermediate point values in the computational domain. As the blood flow velocity changes with time, the blood viscosity value also changes. For this reason, the Carreu model was used in determining the viscosity depending on the velocity. RESULTS Numerical study results showed that when bypassed, pressure and wall shear stresses reduced in the range of 40-70% in the aneurysm. Numerical results obtained are presented in graphs including the variation of pressure, wall shear stress and velocity streamlines in the aneurysm. CONCLUSION Considering the numerical results for all parameter values, it is seen that the most important factors affecting the pressure and WSS values in bypassing are the bypass position on the basilar artery (Lb) and the diameter of the bypass vessel (d). Pressure and wall shear stress reduced in the range of 40-70% in the aneurysm in the case of bypass for all parameters. This demonstrates that pressure and WSS values can be greatly reduced in aneurysm treatment by bypassing in cases where clipping or coil embolization methods can not be applied.
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Affiliation(s)
- Burak Kurşun
- Mechanical Engineering Department, Amasya University, 05100, Turkey
| | - Levent Uğur
- Mechanical Engineering Department, Amasya University, 05100, Turkey.
| | - Gökhan Keskin
- Internal Medical Sciences Department, Amasya University, 05100, Turkey
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Kim MW, An S, Kim K, Kim TG, Jo HS, Park DH, Yoon SS, Yarin AL. Packing of metalized polymer nanofibers for aneurysm embolization. NANOSCALE 2018; 10:6589-6601. [PMID: 29578221 DOI: 10.1039/c7nr09645c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Aneurysmal subarachnoid hemorrhage (SAH) is the extravasation of blood into the subarachnoid space and is fatal in most cases. Platinum coils have been used to fill the hemorrhage site and prevent the extravasation of blood. Here we explored the use of Pt-coated polymer nanofibers (NF) to prevent blood extravasation and were able to achieve improved results in vitro. The polymer nanofibers were produced via electrospinning and were subsequently electroplated with Pt, resulting in metalized nanofibers. These nanofibers were installed within a microfluidic channel, and the resulting reduction in the permeability was evaluated using a fluid similar to blood. Based on the obtained results, these newly developed nanofibers are expected to decrease the operation cost for SAH, owing to their reduced size and low material cost. Furthermore, it is expected that these nanofibers will be used in a smaller amount during SAH operation while having the same preventive effect. This should reduce the operational risk associated with the multiple steps required to place the Pt coils at the SAH site. Finally, the underlying hydrodynamic mechanism responsible for the reduced permeability of the synthesized nanofibers is described.
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Affiliation(s)
- Min-Woo Kim
- School of Mechanical Engineering, Korea University, Seoul 02841, Republic of Korea.
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10
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Computational fluid dynamics (CFD) using porous media modeling predicts recurrence after coiling of cerebral aneurysms. PLoS One 2017; 12:e0190222. [PMID: 29284057 PMCID: PMC5746265 DOI: 10.1371/journal.pone.0190222] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 12/11/2017] [Indexed: 11/19/2022] Open
Abstract
Objective This study aimed to predict recurrence after coil embolization of unruptured cerebral aneurysms with computational fluid dynamics (CFD) using porous media modeling (porous media CFD). Method A total of 37 unruptured cerebral aneurysms treated with coiling were analyzed using follow-up angiograms, simulated CFD prior to coiling (control CFD), and porous media CFD. Coiled aneurysms were classified into stable or recurrence groups according to follow-up angiogram findings. Morphological parameters, coil packing density, and hemodynamic variables were evaluated for their correlations with aneurysmal recurrence. We also calculated residual flow volumes (RFVs), a novel hemodynamic parameter used to quantify the residual aneurysm volume after simulated coiling, which has a mean fluid domain > 1.0 cm/s. Result Follow-up angiograms showed 24 aneurysms in the stable group and 13 in the recurrence group. Mann-Whitney U test demonstrated that maximum size, dome volume, neck width, neck area, and coil packing density were significantly different between the two groups (P < 0.05). Among the hemodynamic parameters, aneurysms in the recurrence group had significantly larger inflow and outflow areas in the control CFD and larger RFVs in the porous media CFD. Multivariate logistic regression analyses demonstrated that RFV was the only independently significant factor (odds ratio, 1.06; 95% confidence interval, 1.01–1.11; P = 0.016). Conclusion The study findings suggest that RFV collected under porous media modeling predicts the recurrence of coiled aneurysms.
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11
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Fujimura S, Takao H, Suzuki T, Dahmani C, Ishibashi T, Mamori H, Yamamoto M, Murayama Y. Hemodynamics and coil distribution with changing coil stiffness and length in intracranial aneurysms. J Neurointerv Surg 2017; 10:797-801. [PMID: 29259122 PMCID: PMC6204941 DOI: 10.1136/neurintsurg-2017-013457] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/25/2017] [Accepted: 11/27/2017] [Indexed: 12/02/2022]
Abstract
Purpose The purpose of this study was to investigate hemodynamics and coil distribution with changing coil stiffness and length using the finite element method (FEM) and computational fluid dynamics (CFD) analysis. Methods Basic side-wall and bifurcation type aneurysm models were used. Six types of coil models were generated by changing the coil stiffness and length, based on commercially available embolic coils. Coil embolization was simulated using FEM. CFD was performed to characterize the hemodynamics in the aneurysms after embolization. Coil distribution and velocity reduction in the aneurysms were evaluated. Results The median value of radial coil distribution was shifted from the center to the outer side of the aneurysmal dome by changing coil stiffness: harder coils entered the outer side of the aneurysmal dome more easily. Short coils were more distributed at the neck region, since their small size made it easy for them to enter the tighter area. CFD results also indicated that velocity in the aneurysm was effectively reduced when the coils were more distributed at the neck region and the outer side of the aneurysmal dome because of the disturbance in blood inflow. Conclusions It is easier for coils to enter the outer side of the aneurysmal sphere when they are harder. If coils are short, they can enter tighter areas more easily. In addition, high coil density at the outer side of the aneurysmal dome and at the neck region is important to achieve effective velocity reduction.
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Affiliation(s)
- Soichiro Fujimura
- Graduate School of Mechanical Engineering, Tokyo University of Science, Tokyo, Japan.,Department of Innovation for Medical Information Technology, The Jikei University School of Medicine, Tokyo, Japan
| | - Hiroyuki Takao
- Department of Innovation for Medical Information Technology, The Jikei University School of Medicine, Tokyo, Japan.,Department of Neurosurgery, The Jikei University School of Medicine, Tokyo, Japan
| | - Takashi Suzuki
- Department of Innovation for Medical Information Technology, The Jikei University School of Medicine, Tokyo, Japan.,Department of Mechanical Engineering, Tokyo University of Science, Tokyo, Japan
| | - Chihebeddine Dahmani
- Department of Neurosurgery, The Jikei University School of Medicine, Tokyo, Japan.,Siemens Healthcare KK, Tokyo, Japan
| | - Toshihiro Ishibashi
- Department of Neurosurgery, The Jikei University School of Medicine, Tokyo, Japan
| | - Hiroya Mamori
- Department of Mechanical Engineering, Tokyo University of Science, Tokyo, Japan
| | - Makoto Yamamoto
- Department of Mechanical Engineering, Tokyo University of Science, Tokyo, Japan
| | - Yuichi Murayama
- Department of Neurosurgery, The Jikei University School of Medicine, Tokyo, Japan
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12
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Nash LD, Browning Monroe MB, Ding YH, Ezell KP, Boyle AJ, Kadirvel R, Kallmes DF, Maitland DJ. Increased X-ray Visualization of Shape Memory Polymer Foams by Chemical Incorporation of Iodine Motifs. Polymers (Basel) 2017; 9. [PMID: 30034862 PMCID: PMC6052870 DOI: 10.3390/polym9080381] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Shape memory polymers can be programmed into a secondary geometry and recovered to their primary geometry with the application of a controlled stimulus. Porous shape memory polymer foam scaffolds that respond to body temperature show particular promise for embolic medical applications. A limitation for the minimally invasive delivery of these materials is an inherent lack of X-ray contrast. In this work, a triiodobenzene containing a monomer was incorporated into a shape memory polymer foam material system to chemically impart X-ray visibility and increase material toughness. Composition and process changes enabled further control over material density and thermomechanical properties. The proposed material system demonstrates a wide range of tailorable functional properties for the design of embolic medical devices, including X-ray visibility, expansion rate, and porosity. Enhanced visualization of these materials can improve the acute performance of medical devices used to treat vascular malformations, and the material porosity provides a healing scaffold for durable occlusion.
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Affiliation(s)
- Landon D. Nash
- Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (L.D.N.); (M.B.B.M.); (K.P.E.); (A.J.B.)
| | - Mary Beth Browning Monroe
- Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (L.D.N.); (M.B.B.M.); (K.P.E.); (A.J.B.)
| | - Yong-Hong Ding
- Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA; (Y.-H.D.); (R.K.); (D.F.K.)
| | - Kendal P. Ezell
- Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (L.D.N.); (M.B.B.M.); (K.P.E.); (A.J.B.)
| | - Anthony J. Boyle
- Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (L.D.N.); (M.B.B.M.); (K.P.E.); (A.J.B.)
| | - Ramanathan Kadirvel
- Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA; (Y.-H.D.); (R.K.); (D.F.K.)
| | - David F. Kallmes
- Department of Radiology, Mayo Clinic, Rochester, MN 55905, USA; (Y.-H.D.); (R.K.); (D.F.K.)
| | - Duncan J. Maitland
- Biomedical Engineering, Texas A&M University, College Station, TX 77843, USA; (L.D.N.); (M.B.B.M.); (K.P.E.); (A.J.B.)
- Correspondence: ; Tel.: +1-979-458-3471
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Use of Micropatterned Thin Film Nitinol in Carotid Stents to Augment Embolic Protection. J Funct Biomater 2016; 7:jfb7040034. [PMID: 27983574 PMCID: PMC5197993 DOI: 10.3390/jfb7040034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/05/2016] [Accepted: 12/09/2016] [Indexed: 12/29/2022] Open
Abstract
Stenting is an alternative to endarterectomy for the treatment of carotid artery stenosis. However, stenting is associated with a higher risk of procedural stroke secondary to distal thromboembolism. Hybrid stents with a micromesh layer have been proposed to address this complication. We developed a micropatterned thin film nitinol (M-TFN) covered stent designed to prevent thromboembolism during carotid intervention. This innovation may obviate the need or work synergistically with embolic protection devices. The proposed double layered stent is low-profile, thromboresistant, and covered with a M-TFN that can be fabricated with fenestrations of varying geometries and sizes. The M-TFN was created in multiple geometries, dimensions, and porosities by sputter deposition. The efficiency of various M-TFN to capture embolic particles was evaluated in different atherosclerotic carotid stenotic conditions through in vitro tests. The covered stent prevented emboli dislodgement in the range of 70%–96% during 30 min duration tests. In vitro vascular cell growth study results showed that endothelial cell elongation, alignment and growth behaviour silhouettes significantly enhance, specifically on the diamond-shape M-TFN, with the dimensions of 145 µm × 20 µm and a porosity of 32%. Future studies will require in vivo testing. Our results demonstrate that M-TFN has a promising potential for carotid artery stenting.
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Nair P, Chong BW, Indahlastari A, Ryan J, Workman C, Haithem Babiker M, Yadollahi Farsani H, Baccin CE, Frakes D. Hemodynamic Characterization of Geometric Cerebral Aneurysm Templates Treated With Embolic Coils. J Biomech Eng 2016; 138:021011. [PMID: 26593324 DOI: 10.1115/1.4032046] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 11/08/2022]
Abstract
Embolic coiling is one of the most effective treatments for cerebral aneurysms (CAs), largely due to the hemodynamic modifications that the treatment effects in the aneurysmal environment. However, coiling can have very different hemodynamic outcomes in aneurysms with different geometries. Previous work in the field of biofluid mechanics has demonstrated on a general level that geometry is a driving factor behind aneurysmal hemodynamics. The goal of this study was to relate two specific geometric factors that describe CAs (i.e., dome size (DS) and parent-vessel contact-angle (PV-CA)) and one factor that describes treatment (i.e., coil packing density (PD)) to three clinically relevant hemodynamic responses (i.e., aneurysmal root-mean-square velocity (Vrms), aneurysmal wall shear stress (WSS), and cross-neck flow (CNF)). Idealized models of basilar tip aneurysms were created in both virtual and physical forms to satisfy two-level multifactorial experimental designs. Steady and pulsatile flow hemodynamics were then evaluated in the virtual models using computational fluid dynamics (CFD) (before and after virtual treatment with finite element (FE) embolic coil models), and hemodynamics were also evaluated in the physical models using particle image velocimetry (PIV) (before and after treatment with actual embolic coils). Results showed that among the factors considered, PD made the greatest contributions to effects on hemodynamic responses in and around the aneurysmal sac (i.e., Vrms and WSS), while DS made the greatest contributions to effects on hemodynamics at the neck (i.e., CNF). Results also showed that while a geometric factor (e.g., PV-CA) may play a relatively minor role in dictating hemodynamics in the untreated case, the same factor can play a much greater role after coiling. We consider the significance of these findings in the context of aneurysmal recurrence and rupture, and explore potential roles for the proposed methods in endovascular treatment planning.
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15
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Babiker MH, Chun Y, Roszelle B, Hafner W, Farsani HY, Gonzalez LF, Albuquerque F, Kealey C, Levi DS, Carman GP, Frakes DH. In Vitro Investigation of a New Thin Film Nitinol-Based Neurovascular Flow Diverter. J Med Device 2016. [DOI: 10.1115/1.4033015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Fusiform and wide-neck cerebral aneurysms (CAs) can be challenging to treat with conventional endovascular or surgical approaches. Recently, flow diverters have been developed to treat these cases by diverting flow away from the aneurysm rather than occluding it. The pipeline embolization device (PED), which embodies a single-layer braided design, is best known among available flow diverters. While the device has demonstrated success in recent trials, late aneurysmal rupture after PED treatment has been a concern. More recently, a new generation of dual-layer devices has emerged that includes a novel hyperelastic thin film nitinol (HE-TFN)-covered design. In this study, we compare fluid dynamic performance between the PED and HE-TFN devices using particle image velocimetry (PIV). The PED has a pore density of 12.5–20 pores/mm2 and a porosity of 65–70%. The two HE-TFN flow diverters have pore densities of 14.75 pores/mm2 and 40 pores/mm2, and porosities of 82% and 77%, respectively. Conventional wisdom suggests that the lower porosity PED would decrease intra-aneurysmal flow to the greatest degree. However, under physiologically realistic pulsatile flow conditions, average drops in root-mean-square (RMS) velocity (VRMS) within the aneurysm of an idealized physical flow model were 42.8–73.7% for the PED and 68.9–82.7% for the HE-TFN device with the highest pore density. Interestingly, examination of collateral vessel flows in the same model also showed that the HE-TFN design allowed for greater collateral perfusion than the PED. Similar trends were observed under steady flow conditions in the idealized model. In a more clinically realistic scenario wherein an anatomical aneurysm model was investigated, the PED affected intra-aneurysmal VRMS reductions of 64.3% and 56.3% under steady and pulsatile flow conditions, respectively. In comparison, the high pore density HE-TFN device reduced intra-aneurysmal VRMS by 88% and 71.3% under steady and pulsatile flow conditions, respectively. We attribute the superior performance of the HE-TFN device to higher pore density, which may play a more important role in modifying aneurysmal fluid dynamics than the conventional flow diverter design parameter of greatest general interest, absolute porosity. Finally, the PED led to more elevated intra-aneurysmal pressures after deployment, which provides insight into a potential mechanism for late rupture following treatment with the device.
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Affiliation(s)
- M. H. Babiker
- Endovantage, LLC, Skysong, Ste. 200, 1475 N. Scottsdale Road, Scottsdale, AZ 85257 e-mail:
| | - Y. Chun
- Department of Industrial Engineering, Swanson School of Engineering, University of Pittsburgh, 1034 Benedum Hall, Pittsburgh, PA 15261
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, 1034 Benedum Hall, Pittsburgh, PA 15261 e-mail:
| | - B. Roszelle
- Department of Mechanical and Materials Engineering, University of Denver, 2390 S. York Street, Denver, CO 80208 e-mail:
| | - W. Hafner
- Department of Physical Medicine and Rehabilitation, University of Colorado, 12631 East 17th Avenue, Aurora, CO 80045 e-mail:
| | - H. Y. Farsani
- School of Biological and Health Systems Engineering, ECG 334, Tempe, AZ 85287-9707 e-mail:
| | - L. F. Gonzalez
- Duke University Hospital, 2301 Erwin Road, Durham, NC 27710 e-mail:
| | - F. Albuquerque
- Barrow Neurological Institute, Saint Joseph's Hospital and Medical Center, 350 W. Thomas Road, Phoenix, AZ 85013 e-mail:
| | - C. Kealey
- Business Development, NeuroSigma, Inc., 10960 Wilshire Boulevard, Suite 1910, Los Angeles, CA 90024 e-mail:
| | - D. S. Levi
- Pediatric Cardiology, Mattel Children's Hospital, UCLA, B2-427, 10833 Le Conte Avenue, Los Angeles, CA 90095-1743 e-mail:
| | - G. P. Carman
- Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, 38-137M, Engineering IV, Los Angeles, CA 90095 e-mail:
| | - D. H. Frakes
- School of Biological and Health Systems Engineering, ECG 334, Tempe, AZ 85287-9707 e-mail:
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Jeong HW, Jin SC. Practical Feasibility and Packing Density of Endovascular Coiling Using Target® Nano™ Coils in Small Cerebral Aneurysms. J Cerebrovasc Endovasc Neurosurg 2016; 17:295-300. [PMID: 27064999 PMCID: PMC4823426 DOI: 10.7461/jcen.2015.17.4.295] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 11/02/2015] [Accepted: 12/17/2015] [Indexed: 11/28/2022] Open
Abstract
Objective Based on the use of Nano™ coils, we retrospectively compared the proportion of the coils (≤ 1.5 mm) and packing density in two patient groups with small cerebral aneurysms (< 4 mm diameter) who were treated with or without Nano™ coils. Materials and Methods Between January 2012 and November 2013, in 548 cerebral aneurysms treated by endovascular coiling, 143 patients with 148 small cerebral aneurysms underwent endovascular coiling. After March 2013, coiling with Nano™ coils was performed on 45 small cerebral aneurysms (30.4%). Results There were no significant differences in the size and locations of the cerebral aneurysms, the age of the patients, and the procedural modalities between the two groups. The proportion of the coil (≤ 1.5 mm) of the group treated with Nano™ coils (53.6%) was higher than the proportion of the coil (≤ 1.5 mm) of the group treated without Nano™ coils (14.7%) with statistical significance (p < 0.001). The packing density of the group treated with Nano™ coils (31.3 ± 9.69%) was higher than the packing density of the group treated without Nano™ coils (29.49 ± 7.84%), although the difference was not significant. Procedural complications developed in 3 lesions (2 thromboembolisms and 1 carotid dissection) (2.0%). Treatment-related transient neurological deficits due to thromboembolism developed in 1 lesion, which had not been treated with Nano™ coils. There was no treatment-related permanent morbidity or mortality in either of the groups. Conclusion In our series, the small cerebral aneurysms treated with Nano™ coils showed more packing density with no additive procedural risk or difficulty.
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Affiliation(s)
- Hae Woong Jeong
- Department of Diagnostic Radiology, Busan Paik Hospital, Inje University, Busan, Korea
| | - Sung-Chul Jin
- Department of Neurosurgery, Inje University Haeundae Paik Hospital, Busan, Korea
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Kaesmacher J, Müller-Leisse C, Huber T, Boeckh-Behrens T, Haller B, Shiban E, Friedrich B, Zimmer C, Dorn F, Prothmann S. Volume versus standard coils in the treatment of intracranial aneurysms. J Neurointerv Surg 2015; 8:1034-40. [PMID: 26491040 DOI: 10.1136/neurintsurg-2015-012014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 09/28/2015] [Indexed: 11/03/2022]
Abstract
BACKGROUND Volume coils were developed to improve occlusion rates of intracranial aneurysms. Previous studies have shown increased packing density and comparable occlusion rates, but subgroup analyses of aneurysm size have not been carried out. OBJECTIVE To evaluate the safety and efficacy of the Penumbra Coil 400 (PC400) system in treating intracranial aneurysms compared with standard diameter coils. METHODS A monocentric retrospective case review of 260 aneurysms in 233 patients was carried out. In 37 aneurysms the PC400 system was used, while 223 aneurysms were treated with conventional coils. Previously treated aneurysms and aneurysms treated with flow diverters were excluded. Aneurysm and procedure characteristics, packing density, postprocedural and follow-up occlusion grades as well as coil compaction were evaluated. RESULTS Aneurysms treated with PC400 coils had higher volume (218.9 vs 47.1 mm(3), p<0.001), wider necks (3.0 vs 2.5 mm, p=0.005), and greater dome/neck ratio (2.0 vs 1.6, p=0.001) in comparison with aneurysms treated with conventional coils. Compared with controls, in the PC400 group we achieved higher packing densities (43.2% vs 34.4%, p<0.001; in aneurysms ≥7 mm 42.2% vs 27.8%, p<0.001). On follow-up angiography we observed less coil compaction (23.8% vs 64.3%, p=0.003) and less aneurysm recurrence (14.3% vs 40.5%, p=0.046) in aneurysms ≥7 mm when using the PC400 system. CONCLUSIONS Use of the PC400 system as opposed to conventional coils suggests that the PC400 system is safe and effective in treating intracranial aneurysms. Despite having been applied in a potentially more difficult-to-treat group, the use of PC400 was associated with less coil compaction and aneurysm recurrence in aneurysms ≥7 mm.
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Affiliation(s)
- Johannes Kaesmacher
- Abteilung für diagnostische und interventionelle Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Christina Müller-Leisse
- Abteilung für diagnostische und interventionelle Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Thomas Huber
- Abteilung für diagnostische und interventionelle Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Tobias Boeckh-Behrens
- Abteilung für diagnostische und interventionelle Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Bernhard Haller
- Institut für Statistik und Epidemiologie (IMSE), Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Ehab Shiban
- Klinik für Neurochirurgie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Benjamin Friedrich
- Klinik und Poliklinik für Diagnostische und Interventionelle Radiologie, Universitätsklinikum Leipzig, Leipzig, Germany
| | - Claus Zimmer
- Abteilung für diagnostische und interventionelle Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Franziska Dorn
- Abteilung für Neuroradiologie, Klinikum Großhadern, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Sascha Prothmann
- Abteilung für diagnostische und interventionelle Neuroradiologie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
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Sadato A, Adachi K, Hayakawa M, Kato Y, Hirose Y. Effects of anatomic characteristics of aneurysms on packing density in endovascular coil embolization: analysis of a single center's experience. Neurosurg Rev 2015. [PMID: 26223542 DOI: 10.1007/s10143-015-0658-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
When embolizing cerebral aneurysms, dense coil packing may prevent recanalization but this may be influenced by the aneurysm morphology. We have analyzed retrospectively the relationship between anatomic features and the volumetric coil packing density. We analyzed 452 aneurysms in 434 patients treated by coil embolization without stenting, expressing packing density as volume embolization ratio (VER, volume of inserted coils/aneurysm volume). Six morphological variables (neck width, height, maximum diameter, dome to neck ratio (DNR), and aspect ratio), aneurysm location, and whether the aneurysm was ruptured or unruptured were analyzed with respect to dense (VER ≥20%) or loose (VER <20%) packing densities, using logistic regression analysis and ROC analysis. Among 452 aneurysms, VERs >20% were achieved for 272 aneurysms, with a mean VER of 24.7%. The mean VER of the remaining 180 aneurysms was 15.6%. In univariate analyses, the predictors for dense packing were having an anterior circulation, DNR, aspect ratio, and neck width. In multivariate analysis, the independent predictors were smaller neck width (odds ratio (OR) 0.8735; 95% confidence interval (CI) 0.7635-0.9993) and larger aspect ratio (OR 1.6679; 95% CI 1.0460-2.6594). ROC analysis showed optimal cutoff values for an aspect ratio of 1.35 (sensitivity 69.5%, specificity 51.7%) and a neck width of 3.13 mm (sensitivity 51.1%, specificity 27.8%). Although dense coil packing is still difficult to achieve in wide-necked aneurysms without the use of stents, packing with VER >20% is expected to be achieved when the height is 1.35 times larger than the neck width.
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Affiliation(s)
- Akiyo Sadato
- Department of Neurosurgery, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan.
| | - Kazuhide Adachi
- Department of Neurosurgery, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Motoharu Hayakawa
- Department of Neurosurgery, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Yoko Kato
- Department of Neurosurgery, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
| | - Yuichi Hirose
- Department of Neurosurgery, Fujita Health University, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi, 470-1192, Japan
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19
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Predictors of treatment failure following coil embolization of intracranial aneurysms. J Clin Neurosci 2015; 22:1275-81. [DOI: 10.1016/j.jocn.2015.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 03/02/2015] [Indexed: 11/23/2022]
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20
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Chen Y, Jankowitz BT, Cho SK, Yeo WH, Chun Y. A novel low-profile flow sensor for monitoring of hemodynamics in cerebral aneurysm. ACTA ACUST UNITED AC 2015. [DOI: 10.12989/bme.2015.2.2.071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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21
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Chueh JY, Vedantham S, Wakhloo AK, Carniato SL, Puri AS, Bzura C, Coffin S, Bogdanov AA, Gounis MJ. Aneurysm permeability following coil embolization: packing density and coil distribution. J Neurointerv Surg 2014; 7:676-81. [PMID: 25031179 PMCID: PMC4552888 DOI: 10.1136/neurintsurg-2014-011289] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 06/29/2014] [Indexed: 11/25/2022]
Abstract
Background Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability. Methods Aneurysm models were coiled using either Guglielmi detachable coils or Target coils. The permeability was assessed by taking the ratio of microspheres passing through the coil mass to those in the working fluid. Aneurysms containing coil masses were sectioned for image analysis to determine surface area fraction and coil uniformity. Results All aneurysms were coiled to a packing density of at least 27%. Packing density, surface area fraction of the dome and neck, and uniformity of the dome were significantly correlated (p<0.05). Hence, multivariate principal components-based partial least squares regression models were used to predict permeability. Similar loading vectors were obtained for packing and uniformity measures. Coil mass permeability was modeled better with the inclusion of packing and uniformity measures of the dome (r2=0.73) than with packing density alone (r2=0.45). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. Conclusions A densely packed aneurysm with a high degree of coil mass uniformity will reduce permeability.
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Affiliation(s)
- Ju-Yu Chueh
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Srinivasan Vedantham
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Ajay K Wakhloo
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Sarena L Carniato
- PreClinical Science, Stryker Neurovascular, Fremont, California, USA
| | - Ajit S Puri
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Conrad Bzura
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Spencer Coffin
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Alexei A Bogdanov
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Matthew J Gounis
- Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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Goubergrits L, Schaller J, Kertzscher U, Woelken T, Ringelstein M, Spuler A. Hemodynamic impact of cerebral aneurysm endovascular treatment devices: coils and flow diverters. Expert Rev Med Devices 2014; 11:361-73. [PMID: 24918904 DOI: 10.1586/17434440.2014.925395] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Coils and flow diverters or stents are devices successfully used to treat cerebral aneurysms. Treatment aims to reduce intra-aneurysmal flow, thereby separating the aneurysmal sac from the blood circulation. The focus and this manuscript combining literature review and our original research is an analysis of changes in aneurysmal hemodynamics caused by endovascular treatment devices. Knowledge of post-treatment hemodynamics is a path to successful long-term treatment. Summarizing findings on hemodynamic impact of treatment devices, we conclude: coiling and stenting do not affect post-treatment intra-aneurysmal pressure, but significantly alter aneurysmal hemodynamics through flow reduction and a change in flow structure. The impact of treatment devices on aneurysmal flow depends, however, on a set of parameters including device geometry, course of placement, parent vessel and aneurysm geometry.
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Affiliation(s)
- Leonid Goubergrits
- Biofluid Mechanics Laboratory, Charité-Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany
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Results of endovascular treatment of aneurysms depending on their size, volume and coil packing density. Neurol Neurochir Pol 2014; 47:467-75. [PMID: 24166568 DOI: 10.5114/ninp.2013.38226] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND AND PURPOSE In contrast to neurosurgery, which is more efficient, endovascular treatment (EVT) is less invasive. The main purpose of EVT is complete occlusion of the aneurysm and protection from subarachnoid haemorrhage. Accurate measurements of the aneurysm (size, volume) obtained using a 3D digital subtraction angiography (DSA) workstation can assist in the proper assessment of coil packing density (CPD), which affects possible distant recanalization. The main disadvantage of endovascular treatment of intracranial aneurysms compared to neurosurgery is the high recurrence rate. We evaluated the results of endovascular treatment of aneurysms depending on their size, volume and coil packing density. MATERIAL AND METHODS Thirty-five patients with intracranial aneurysms underwent endovascular embolization with bare platinum coils. Three-dimensional DSA was used to evaluate aneurysms' morphology. Eighteen patients underwent 3D DSA follow-up 6-45 months after treatment. Initial and follow-up results of embolization were assessed with the Raymond-Montreal scale. The impact of aneurysms' morphology, volume and initial CPD on endovascular treatment was evaluated. RESULTS Among 35 patients, complete initial embolization was achieved in 74%. Mean initial aneurysm volume in 3D DSA was 0.517 mL and decreased significantly after embolization. Initial CPD varied from 74% to 2% depending on aneurysm diameter (12.1% for aneurysms ≥ 10 mm, 22.5% for aneurysms < 10 mm). Results of embolization on the Raymond-Montreal scale significantly depended on aneurysms' CPD. Aneurysms' recanalization rate on 3D DSA follow-up was 36%, with complete recanalization in 3.3%. CONCLUSIONS We can achieve a better outcome if size and volume of the aneurysm sac is smaller and if CPD is higher.
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Babiker MH, Chong B, Gonzalez LF, Cheema S, Frakes DH. Finite element modeling of embolic coil deployment: multifactor characterization of treatment effects on cerebral aneurysm hemodynamics. J Biomech 2013; 46:2809-16. [PMID: 24119679 DOI: 10.1016/j.jbiomech.2013.08.021] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Revised: 08/27/2013] [Accepted: 08/31/2013] [Indexed: 10/26/2022]
Abstract
Endovascular coiling is the most common treatment for cerebral aneurysms. During the treatment, a sequence of embolic coils with different stiffness, shapes, sizes, and lengths is deployed to fill the aneurysmal sac. Although coil packing density has been clinically correlated with treatment success, many studies have also reported success at low packing densities, as well as recurrence at high packing densities. Such reports indicate that other factors may influence treatment success. In this study, we used a novel finite element approach and computational fluid dynamics (CFD) to investigate the effects of packing density, coil shape, aneurysmal neck size, and parent vessel flow rate on aneurysmal hemodynamics. The study examines a testbed of 80 unique CFD simulations of post-treatment flows in idealized basilar tip aneurysm models. Simulated coil deployments were validated against in vitro and in vivo deployments. Among the investigated factors, packing density had the largest effect on intra-aneurysmal velocities. However, multifactor analysis of variance showed that coil shape can also have considerable effects, depending on packing density and neck size. Further, linear regression analysis showed an inverse relationship between mean void diameter in the aneurysm and mean intra-aneurysmal velocities, which underscores the importance of coil distribution and thus coil shape. Our study suggests that while packing density plays a key role in determining post-treatment hemodynamics, other factors such as coil shape, aneurysmal geometry, and parent vessel flow may also be very important.
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Affiliation(s)
- M Haithem Babiker
- School of Biological and Health Systems Engineering, Arizona State University, 501 E. Tyler, ECG 334, P.O. Box 879709, Tempe, AZ 85287-9709, United States.
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25
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Pandey AS, San Antonio JD, Addya S, Surrey S, Fortina P, Van Bockstaele EJ, Veznedaroglu E. Mechanisms of endothelial cell attachment, proliferation, and differentiation on 4 types of platinum-based endovascular coils. World Neurosurg 2013; 82:684-95. [PMID: 23994074 DOI: 10.1016/j.wneu.2013.08.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 06/10/2013] [Accepted: 08/15/2013] [Indexed: 11/19/2022]
Abstract
OBJECTIVE A subarachnoid hemorrhage is neurologically devastating, with 50% of patients becoming disabled or deceased. Advent of Guglielmi detachable coils in 1995 permitted endovascular treatment of cerebral aneurysms. Coiling is efficacious and safe, but durability needs improvement, as nearly 20% of patients require further invasive intervention secondary to aneurysm recurrence. The aim of this study is to develop an in vitro model of endothelial cell (EC) proliferation and differentiation on four types of platinum-based coils, using gene expression profiling to understand EC biology as they colonize and differentiate on coils. METHODS Human umbilical vein ECs were grown in vitro on platinum coil segments. Growth patterns were assessed as a function of coil type. Gene expression profiles for coil attached versus coil unattached ECs were determined using immunohistochemistry and gene array analysis. RESULTS ECs showed rapid, robust attachment to all coil types. Some detachment occurred within 24-48 hours. Significant growth of remaining attached cells occurred during the next week, creating a confluence on coils and within coil grooves. Similar growth curve results were obtained with human brain ECs on platinum-based coil surfaces. Differentiation markers in attached cells (α(1), α(2), β(1) integrins) were expressed on immunostaining, whereas microarray gene expression revealed 48 up-regulated and 68 down-regulated genes after 24-hour growth on coils. Major pathways affected as a function of time of colonization on coils and coil type included those involved in regulation of cell cycle and cell signaling. CONCLUSIONS We developed an in vitro model for evaluating endothelialization of platinum coils to optimize coil design to support robust EC colonization and differentiation.
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Affiliation(s)
- Aditya S Pandey
- Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan, USA.
| | | | - Sankar Addya
- Department of Cancer Biology, Cancer Genomics Laboratory, Kimmel Cancer Center, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, USA
| | - Saul Surrey
- Department of Medicine, Cardeza Foundation for Hematologic Research, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, USA
| | - Paolo Fortina
- Department of Cancer Biology, Cancer Genomics Laboratory, Kimmel Cancer Center, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, USA; Department of Molecular Medicine, University La Sapienza, Rome, Italy
| | - Elisabeth J Van Bockstaele
- Department of Neurosurgery, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania, USA
| | - Erol Veznedaroglu
- Stroke and Cerebrovascular Center of New Jersey, Capital Health System, Trenton, New Jersey, USA
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Jeong W, Han MH, Rhee K. Effects of framing coil shape, orientation, and thickness on intra-aneurysmal flow. Med Biol Eng Comput 2013; 51:981-90. [DOI: 10.1007/s11517-013-1073-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 03/29/2013] [Indexed: 11/30/2022]
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27
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Babiker MH, Gonzalez LF, Albuquerque F, Collins D, Elvikis A, Zwart C, Roszelle B, Frakes DH. An In Vitro Study of Pulsatile Fluid Dynamics in Intracranial Aneurysm Models Treated with Embolic Coils and Flow Diverters. IEEE Trans Biomed Eng 2013. [DOI: 10.1109/tbme.2012.2228002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Roszelle BN, Gonzalez LF, Babiker MH, Ryan J, Albuquerque FC, Frakes DH. Flow diverter effect on cerebral aneurysm hemodynamics: an in vitro comparison of telescoping stents and the Pipeline. Neuroradiology 2013; 55:751-8. [PMID: 23515661 DOI: 10.1007/s00234-013-1169-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 03/04/2013] [Indexed: 11/27/2022]
Abstract
INTRODUCTION Flow diverting devices and stents can be used to treat cerebral aneurysms too difficult to treat with coiling or craniotomy and clipping. However, the hemodynamic effects of these devices have not been studied in depth. The objective of this study was to quantify and understand the fluid dynamic changes that occur within bifurcating aneurysms when treated with different devices and configurations. METHODS Two physical models of bifurcating cerebral aneurysms were constructed: an idealized model and a patient-specific model. The models were treated with four device configurations: a single low-porosity Pipeline embolization device (PED) and one, two, and three high-porosity Enterprise stents deployed in a telescoping fashion. Particle image velocimetry was used to measure the fluid dynamics within the aneurysms; pressure was measured within the patient-specific model. RESULTS The PED resulted in the greatest reductions in fluid dynamic activity within the aneurysm for both models. However, a configuration of three telescoping stents reduced the fluid dynamic activity within the aneurysm similarly to the PED treatment. Pressure within the patient-specific aneurysm did not show significant changes among the treatment configurations; however, the pressure difference across the untreated vessel side of the model was greatest with the PED. CONCLUSION Treatment with stents and a flow diverter led to reductions in aneurysmal fluid dynamic activity for both idealized and patient-specific models. While the PED resulted in the greatest flow reductions, telescoping high-porosity stents performed similarly and may represent a viable treatment alternative in situations where the use of a PED is not an option.
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Affiliation(s)
- Breigh N Roszelle
- School of Biological and Health Systems Engineering, Arizona State University, P.O. Box 879709, Tempe, AZ 85287-9709, USA.
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Morales HG, Larrabide I, Geers AJ, San Román L, Blasco J, Macho JM, Frangi AF. A virtual coiling technique for image-based aneurysm models by dynamic path planning. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:119-129. [PMID: 23008248 DOI: 10.1109/tmi.2012.2219626] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Computational algorithms modeling the insertion of endovascular devices, such as coil or stents, have gained an increasing interest in recent years. This scientific enthusiasm is due to the potential impact that these techniques have to support clinicians by understanding the intravascular hemodynamics and predicting treatment outcomes. In this work, a virtual coiling technique for treating image-based aneurysm models is proposed. A dynamic path planning was used to mimic the structure and distribution of coils inside aneurysm cavities, and to reach high packing densities, which is desirable by clinicians when treating with coils. Several tests were done to evaluate the performance on idealized and image-based aneurysm models. The proposed technique was validated using clinical information of real coiled aneurysms. The virtual coiling technique reproduces the macroscopic behavior of inserted coils and properly captures the densities, shapes and coil distributions inside aneurysm cavities. A practical application was performed by assessing the local hemodynamic after coiling using computational fluid dynamics (CFD). Wall shear stress and intra-aneurysmal velocities were reduced after coiling. Additionally, CFD simulations show that coils decrease the amount of contrast entering the aneurysm and increase its residence time.
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Affiliation(s)
- Hernán G Morales
- Center for Computational Imaging and Simulation Technologies in Biomedicine (CISTIB), Information and Communications Technologies Department, Universitat Pompeu Fabra (UPF), Barcelona, Spain.
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Roszelle BN, Babiker MH, Hafner W, Gonzalez LF, Albuquerque FC, Frakes DH. In vitro and in silico study of intracranial stent treatments for cerebral aneurysms: effects on perforating vessel flows. J Neurointerv Surg 2012; 5:354-60. [PMID: 22735859 DOI: 10.1136/neurintsurg-2012-010322] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Many cerebral aneurysms can be treated effectively with intracranial stents. Unfortunately, stents can occlude perforating vessels near the treatment site which can decrease cerebral perfusion and increase the risk of stroke. METHODS Particle image velocimetry was used to investigate the effects of intracranial stents on flows in perforators near a treated aneurysm. In Phase 1 of the study, different stent configurations were deployed into an idealized physical model of a sidewall aneurysm with perforating vessels. The configurations investigated were the Pipeline embolization device (PED) and one, two and three telescoping Neuroform stents. In Phase 2 of the study a single Neuroform stent was deployed so that the stent struts directly occluded the perforating vessel. RESULTS In Phase 1 of the study it was found that even three telescoping stents affected perforating vessel flow less than a single PED under pulsatile conditions (average reduction 32.7% vs 46.5%). Results from Phase 2 indicated that the location of the occluding strut across the perforating vessel orifice had a greater impact on perforating vessel flow than the percentage occlusion. CONCLUSION The findings of this study show that the use, configuration and positioning of intracranial stents can all have considerable influence on flow in affected perforating vessels near treated cerebral aneurysms.
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Affiliation(s)
- Breigh Nonte Roszelle
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287–9709, USA.
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Ugron Á, Szikora I, Paál G. Haemodynamic changes induced by intrasaccular packing on intracranial aneurysms: A computational fluid dynamic study. Interv Med Appl Sci 2012. [DOI: 10.1556/imas.4.2012.2.4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Abstract
Endovascular treatment of intracranial aneurysms is a routine medical practice. The most widely used technique is the packing the aneurysm sac with an embolic material. To gain deeper understanding in the effects of specific treatment methods, the intra-aneurysmal haemodynamics are studied with the help of patient-specific computational models. Numerical simulations demonstrated that embolisation with liquid polymer results in an overall decrease of the wall shear stress and pressure in the aneurysm region. Within the range of clinically relevant packing density, simulation of coil embolisation showed homogenisation and decrease of the wall loads on the aneurysm sac. Increasing the packing density above 20% produces little or no further reduction of intra-aneurysmal flow. Sufficient packing of the aneurysm sac results in significant intra-aneurysmal flow decrease associated with reduced wall loads but locally increased pressure or wall shear stress zones may appear depending on the specific vessel geometry.
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Affiliation(s)
- Ádám Ugron
- 1 Department of Hydrodynamic Systems, Budapest University of Technology and Economics, Budapest, Hungary
- 3 Budapest University of Technology and Economics, P.O. Box 91, H-1521, Budapest, Hungary
| | - István Szikora
- 2 National Institute of Neurosciences, Budapest, Hungary
| | - György Paál
- 1 Department of Hydrodynamic Systems, Budapest University of Technology and Economics, Budapest, Hungary
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The Role of 3 Tesla MRA in the Detection of Intracranial Aneurysms. Int J Vasc Med 2012; 2012:792834. [PMID: 22292121 PMCID: PMC3265088 DOI: 10.1155/2012/792834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2011] [Accepted: 10/09/2011] [Indexed: 12/01/2022] Open
Abstract
Intracranial aneurysms constitute a common pathological entity, affecting approximately 1–8% of the general population. Their early detection is essential for their prompt treatment. Digital subtraction angiography is considered the imaging method of choice. However, other noninvasive methodologies such as CTA and MRA have been employed in the investigation of patients with suspected aneurysms. MRA is a noninvasive angiographic modality requiring no radiation exposure. However, its sensitivity and diagnostic accuracy were initially inadequate. Several MRA techniques have been developed for overcoming all these drawbacks and for improving its sensitivity. 3D TOF MRA and contrast-enhanced MRA are the most commonly employed techniques. The introduction of 3 T magnetic field further increased MRA's sensitivity, allowing detection of aneurysms smaller than 3 mm. The development of newer MRA techniques may provide valuable information regarding the flow characteristics of an aneurysm. Meticulous knowledge of MRA's limitations and pitfalls is of paramount importance for avoiding any erroneous interpretation of its findings.
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Babiker MH, Gonzalez LF, Ryan J, Albuquerque F, Collins D, Elvikis A, Frakes DH. Influence of stent configuration on cerebral aneurysm fluid dynamics. J Biomech 2012; 45:440-7. [PMID: 22226405 DOI: 10.1016/j.jbiomech.2011.12.016] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 12/14/2011] [Accepted: 12/15/2011] [Indexed: 10/14/2022]
Abstract
Embolic coiling is the most popular endovascular treatment available for cerebral aneurysms. Nevertheless, the embolic coiling of wide-neck aneurysms is challenging and, in many cases, ineffective. Use of highly porous stents to support coiling of wide-neck aneurysms has become a common procedure in recent years. Several studies have also demonstrated that high porosity stents alone can significantly alter aneurysmal hemodynamics, but differences among different stent configurations have not been fully characterized. As a result, it is usually unclear which stent configuration is optimal for treatment. In this paper, we present a flow study that elucidates the influence of stent configuration on cerebral aneurysm fluid dynamics in an idealized wide-neck basilar tip aneurysm model. Aneurysmal fluid dynamics for three different stent configurations (half-Y, Y and, cross-bar) were first quantified using particle image velocimetry and then compared. Computational fluid dynamics (CFD) simulations were also conducted for selected stent configurations to facilitate validation and provide more detailed characterizations of the fluid dynamics promoted by different stent configurations. In vitro results showed that the Y stent configuration reduced cross-neck flow most significantly, while the cross-bar configuration reduced velocity magnitudes within the aneurysmal sac most significantly. The half-Y configuration led to increased velocity magnitudes within the aneurysmal sac at high parent-vessel flow rates. Experimental results were in strong agreement with CFD simulations. Simulated results indicated that differences in fluid dynamic performance among the different stent configurations can be attributed primarily to protruding struts within the bifurcation region.
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Affiliation(s)
- M Haithem Babiker
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287-9709, United States.
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Morales HG, Kim M, Vivas EE, Villa-Uriol MC, Larrabide I, Sola T, Guimaraens L, Frangi AF. How do coil configuration and packing density influence intra-aneurysmal hemodynamics? AJNR Am J Neuroradiol 2011; 32:1935-41. [PMID: 21885712 DOI: 10.3174/ajnr.a2635] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Endovascular coiling is a well-established therapy for treating intracranial aneurysms. Nonetheless, postoperative hemodynamic changes induced by this therapy remain not fully understood. The purpose of this work is to assess the influence of coil configuration and packing density on intra-aneurysmal hemodynamics. MATERIALS AND METHODS Three 3D rotational angiography images of 3 intracranial aneurysms before and after endovascular coiling were used. For each aneurysm, a 3D representation of the vasculature was obtained after the segmentation of the images. Afterward, a virtual coiling technique was used to treat the aneurysm geometries with coil models. The aneurysms were coiled with 5 packing densities, and each was generated by using 3 coil configurations. Computational fluid dynamics analyses were carried out in both untreated and treated aneurysm geometries. Statistical tests were performed to evaluate the relative effect of coil configuration on local hemodynamics. RESULTS The intra-aneurysmal blood flow velocity and wall shear stress were diminished as packing density increased. Aneurysmal flow velocity was reduced >50% due to the first inserted coils (packing density <12%) but with a high dependency on coil configuration. Nonsignificant differences (P > .01) were found in the hemodynamics due to coil configuration for high packing densities (near 30%). A damping effect was observed on the intra-aneurysmal blood flow waveform after coiling. CONCLUSIONS Intra-aneurysmal hemodynamics are altered by coils. Coil configuration might reduce its influence on intra-aneurysmal hemodynamics as the packing density increases until an insignificant influence could be achieved for high packing densities.
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Affiliation(s)
- H G Morales
- Center for Computational Imaging & Simulation Technologies in Biomedicine, Information & Communication Technologies Department, Universitat Pompeu Fabra, Barcelona, Spain.
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