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Csippa B, Sándor L, Závodszky G, Szikora I, Paál G. Comparison of Flow Reduction Efficacy of Nominal and Oversized Flow Diverters Using a Novel Measurement-assisted in Silico Method. Clin Neuroradiol 2024:10.1007/s00062-024-01404-4. [PMID: 38652163 DOI: 10.1007/s00062-024-01404-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 03/07/2024] [Indexed: 04/25/2024]
Abstract
PURPOSE The high efficacy of flow diverters (FD) in the case of wide-neck aneurysms is well demonstrated, yet new challenges have arisen because of reported posttreatment failures and the growing number of new generation of devices. Our aim is to present a measurement-supported in silico workflow that automates the virtual deployment and subsequent hemodynamic analysis of FDs. In this work, the objective is to analyze the effects of FD deployment variability of two manufacturers on posttreatment flow reduction. METHODS The virtual deployment procedure is based on detailed mechanical calibration of the flow diverters, while the flow representation is based on hydrodynamic resistance (HR) measurements. Computational fluid dynamic simulations resulted in 5 untreated and 80 virtually treated scenarios, including 2 FD designs in nominal and oversized deployment states. The simulated aneurysmal velocity reduction (AMVR) is correlated with the HR values and deployment scenarios. RESULTS The linear HR coefficient and AMVR revealed a power-law relationship considering all 80 deployments. In nominal deployment scenarios, a significantly larger average AMVR was obtained (60.3%) for the 64-wire FDs than for 48-wire FDs (51.9%). In oversized deployments, the average AMVR was almost the same for 64-wire and 48-wire device types, 27.5% and 25.7%, respectively. CONCLUSION The applicability of our numerical workflow was demonstrated, also in large-scale hemodynamic investigations. The study revealed a robust power-law relationship between a HR coefficient and AMVR. Furthermore, the 64 wire configurations in nominal sizing produced a significantly higher posttreatment flow reduction, replicating the results of other in vitro studies.
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Affiliation(s)
- Benjamin Csippa
- Department of Hydrodynamic Systems, Faculty of Mechanical Engineering,, Budapest University of Technology and Economics, Műegyetem rkp 1-3, 1111, Budapest, Hungary.
| | - Levente Sándor
- Department of Hydrodynamic Systems, Faculty of Mechanical Engineering,, Budapest University of Technology and Economics, Műegyetem rkp 1-3, 1111, Budapest, Hungary
| | - Gábor Závodszky
- Department of Hydrodynamic Systems, Faculty of Mechanical Engineering,, Budapest University of Technology and Economics, Műegyetem rkp 1-3, 1111, Budapest, Hungary
- Faculty of Science, Informatics Institute, Computational Science Lab, University of Amsterdam, Amsterdam, The Netherlands
| | - István Szikora
- National Institute of Mental Health, Neurology, and Neurosurgery, Department of Neurointerventions, Budapest, Hungary
| | - György Paál
- Department of Hydrodynamic Systems, Faculty of Mechanical Engineering,, Budapest University of Technology and Economics, Műegyetem rkp 1-3, 1111, Budapest, Hungary
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2
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Jang LK, Alvarado JA, Pepona M, Wasson EM, Nash LD, Ortega JM, Randles A, Maitland DJ, Moya ML, Hynes WF. Three-dimensional bioprinting of aneurysm-bearing tissue structure for endovascular deployment of embolization coils. Biofabrication 2020; 13. [DOI: 10.1088/1758-5090/abbb9b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 09/25/2020] [Indexed: 01/30/2023]
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3
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Texakalidis P, Sweid A, Mouchtouris N, Peterson EC, Sioka C, Rangel-Castilla L, Reavey-Cantwell J, Jabbour P. Aneurysm Formation, Growth, and Rupture: The Biology and Physics of Cerebral Aneurysms. World Neurosurg 2019; 130:277-284. [DOI: 10.1016/j.wneu.2019.07.093] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/08/2019] [Accepted: 07/09/2019] [Indexed: 12/18/2022]
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4
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Patel AM, Li JKJ, Finegan B, McMurtry MS. Aortic Pressure Estimation Using Blind Identification Approach on Single Input Multiple Output Nonlinear Wiener Systems. IEEE Trans Biomed Eng 2018; 65:1193-1200. [DOI: 10.1109/tbme.2017.2688425] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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5
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Rafat M, Stone HA, Auguste DT, Dabagh M, Randles A, Heller M, Rabinov JD. Impact of diversity of morphological characteristics and Reynolds number on local hemodynamics in basilar aneurysms. AIChE J 2018. [DOI: 10.1002/aic.16091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Marjan Rafat
- School of Engineering and Applied SciencesHarvard UniversityCambridge MA 02138
| | - Howard A. Stone
- School of Engineering and Applied SciencesHarvard UniversityCambridge MA 02138
| | - Debra T. Auguste
- School of Engineering and Applied SciencesHarvard UniversityCambridge MA 02138
| | - Mahsa Dabagh
- Dept. of Biomedical EngineeringDuke UniversityDurham NC 27708
| | - Amanda Randles
- Dept. of Biomedical EngineeringDuke UniversityDurham NC 27708
| | - Martin Heller
- Dept. of Micro‐ and NanotechnologyTechnical University of Denmark, DTU NanotechKongens Lyngby DK‐2800 Denmark
| | - James D. Rabinov
- Dept. of Radiology and NeurosurgeryMassachusetts General HospitalBoston MA 02114
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6
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Syed H, Unnikrishnan VU, Olcmen S. Characteristics of time-varying intracranial pressure on blood flow through cerebral artery: A fluid–structure interaction approach. Proc Inst Mech Eng H 2015; 230:111-21. [DOI: 10.1177/0954411915619952] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 11/03/2015] [Indexed: 01/12/2023]
Abstract
Elevated intracranial pressure is a major contributor to morbidity and mortality in severe head injuries. Wall shear stresses in the artery can be affected by increased intracranial pressures and may lead to the formation of cerebral aneurysms. Earlier research on cerebral arteries and aneurysms involves using constant mean intracranial pressure values. Recent advancements in intracranial pressure monitoring techniques have led to measurement of the intracranial pressure waveform. By incorporating a time-varying intracranial pressure waveform in place of constant intracranial pressures in the analysis of cerebral arteries helps in understanding their effects on arterial deformation and wall shear stress. To date, such a robust computational study on the effect of increasing intracranial pressures on the cerebral arterial wall has not been attempted to the best of our knowledge. In this work, fully coupled fluid–structure interaction simulations are carried out to investigate the effect of the variation in intracranial pressure waveforms on the cerebral arterial wall. Three different time-varying intracranial pressure waveforms and three constant intracranial pressure profiles acting on the cerebral arterial wall are analyzed and compared with specified inlet velocity and outlet pressure conditions. It has been found that the arterial wall experiences deformation depending on the time-varying intracranial pressure waveforms, while the wall shear stress changes at peak systole for all the intracranial pressure profiles.
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Affiliation(s)
- Hasson Syed
- Department of Aerospace Engineering and Mechanics, The University of Alabama, Tuscaloosa, AL, USA
| | - Vinu U Unnikrishnan
- Department of Aerospace Engineering and Mechanics, The University of Alabama, Tuscaloosa, AL, USA
| | - Semih Olcmen
- Department of Aerospace Engineering and Mechanics, The University of Alabama, Tuscaloosa, AL, USA
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7
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Tang AYS, Chung WC, Liu ETY, Qu JQ, Tsang ACO, Leung GKK, Leung KM, Yu ACH, Chow KW. Computational Fluid Dynamics Study of Bifurcation Aneurysms Treated with Pipeline Embolization Device: Side Branch Diameter Study. J Med Biol Eng 2015; 35:293-304. [PMID: 26167140 PMCID: PMC4491114 DOI: 10.1007/s40846-015-0046-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 08/16/2014] [Indexed: 11/17/2022]
Abstract
An intracranial aneurysm, abnormal swelling of the cerebral artery, may lead to undesirable rates of mortality and morbidity upon rupture. Endovascular treatment involves the deployment of a flow-diverting stent that covers the aneurysm orifice, thereby reducing the blood flow into the aneurysm and mitigating the risk of rupture. In this study, computational fluid dynamics analysis is performed on a bifurcation model to investigate the change in hemodynamics with various side branch diameters. The condition after the deployment of a pipeline embolization device is also simulated. Hemodynamic factors such as flow velocity, pressure, and wall shear stress are studied. Aneurysms with a larger side branch vessel might have greater risk after treatment in terms of hemodynamics. Although a stent could lead to flow reduction entering the aneurysm, it would drastically alter the flow rate inside the side branch vessel. This may result in side-branch hypoperfusion subsequent to stenting. In addition, two patient-specific bifurcation aneurysms are tested, and the results show good agreement with the idealized models. Furthermore, the peripheral resistance of downstream vessels is investigated by varying the outlet pressure conditions. This quantitative analysis can assist in treatment planning and therapeutic decision-making.
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Affiliation(s)
- Abraham Yik-Sau Tang
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, 999077 China
| | - Wai-Choi Chung
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, 999077 China
| | - Eric Tian-Yang Liu
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, 999077 China
| | - Jie-Qiong Qu
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, 999077 China
| | - Anderson Chun-On Tsang
- Division of Neurosurgery, Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong, 999077 China
| | - Gilberto Ka-Kit Leung
- Division of Neurosurgery, Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong, 999077 China
| | - Kar-Ming Leung
- Department of Neurosurgery, Kwong Wah Hospital, Waterloo Road, Hong Kong, 999077 China
| | - Alfred Cheuk-Hang Yu
- Medical Engineering Program, Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, 999077 China
| | - Kwok-Wing Chow
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, 999077 China
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Lagrangian postprocessing of computational hemodynamics. Ann Biomed Eng 2014; 43:41-58. [PMID: 25059889 DOI: 10.1007/s10439-014-1070-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 07/11/2014] [Indexed: 10/25/2022]
Abstract
Recent advances in imaging, modeling, and computing have rapidly expanded our capabilities to model hemodynamics in the large vessels (heart, arteries, and veins). This data encodes a wealth of information that is often under-utilized. Modeling (and measuring) blood flow in the large vessels typically amounts to solving for the time-varying velocity field in a region of interest. Flow in the heart and larger arteries is often complex, and velocity field data provides a starting point for investigating the hemodynamics. This data can be used to perform Lagrangian particle tracking, and other Lagrangian-based postprocessing. As described herein, Lagrangian methods are necessary to understand inherently transient hemodynamic conditions from the fluid mechanics perspective, and to properly understand the biomechanical factors that lead to acute and gradual changes of vascular function and health. The goal of the present paper is to review Lagrangian methods that have been used in post-processing velocity data of cardiovascular flows.
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Lee CJ, Srinivas K, Qian Y. Three-dimensional hemodynamic design optimization of stents for cerebral aneurysms. Proc Inst Mech Eng H 2014; 228:213-24. [DOI: 10.1177/0954411914523405] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Flow-diverting stents occlude aneurysms by diverting the blood flow from entering the aneurysm sac. Their effectiveness is determined by the thrombus formation rate, which depends greatly on stent design. The aim of this study was to provide a general framework for efficient stent design using design optimization methods, with a focus on stent hemodynamics as the starting point. Kriging method was used for completing design optimization. Three different cases of idealized stents were considered, and 40–60 samples from each case were evaluated using computational fluid dynamics. Using maximum velocity and vorticity reduction as objective functions, the optimized designs were identified from the samples. A number of optimized stent designs have been found from optimization, which revealed that a combination of high pore density and thin struts is desired. Additionally, distributing struts near the proximal end of aneurysm neck was found to be effective. The success of the methods and framework devised in this study offers a future possibility of incorporating other disciplines to carry out multidisciplinary design optimization.
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Affiliation(s)
- Chang-Joon Lee
- The Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, Australia
| | - Karkenahalli Srinivas
- The Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, Australia
| | - Yi Qian
- The Australian School of Advanced Medicine, Macquarie University, Sydney, NSW, Australia
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10
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Lee CJ, Zhang Y, Takao H, Murayama Y, Qian Y. A fluid-structure interaction study using patient-specific ruptured and unruptured aneurysm: the effect of aneurysm morphology, hypertension and elasticity. J Biomech 2013; 46:2402-10. [PMID: 23962529 DOI: 10.1016/j.jbiomech.2013.07.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 07/17/2013] [Accepted: 07/18/2013] [Indexed: 10/26/2022]
Abstract
Fluid-structure interaction (FSI) simulations using five patient-specific aneurysm geometries are carried out to investigate the difference between ruptured and unruptured aneurysms. Two different blood pressure conditions (normal and hypertension, for all cases), and two different values of elastic modulus (1 and 2MPa, for two cases) are tested. Ruptured aneurysms (RA) generally displayed larger displacement at the dome, lower area-average WSS and higher von Mises stress than unruptured aneurysms (URA) regardless of elasticity or blood pressure condition. RAs had a longitudinal expansion whereas URAs had a radial expansion, which was the key difference between the two types. The difference in expansion pattern may be one of the keys to explaining aneurysm rupture, and further analysis is required in the future to confirm this theory.
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Affiliation(s)
- C J Lee
- The Australian School of Advanced Medicine, Macquarie University, Sydney, Australia
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11
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Lee CJ, Zhang Y, Takao H, Murayama Y, Qian Y. The influence of elastic upstream artery length on fluid-structure interaction modeling: a comparative study using patient-specific cerebral aneurysm. Med Eng Phys 2013; 35:1377-84. [PMID: 23664305 DOI: 10.1016/j.medengphy.2013.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 01/15/2013] [Accepted: 03/13/2013] [Indexed: 10/26/2022]
Abstract
Fluid-structure interaction (FSI) simulations using a patient-specific geometry are carried out to investigate the influence the length of elastic parent artery and the position of constraints in the solid domain on the accuracy of patient-specific FSI simulations. Three models are tested: Long, Moderate, and Short, based on the length of the elastic parent artery. All three models use same wall thickness (0.5 mm) and the elastic modulus (5 MPa). The maximum mesh displacement is the largest for the Long model (0.491 mm) compared to other models (0.3 mm for Moderate, and 0.132 mm for Short). The differences of hemodynamic and mechanical variables, aneurysm volume and cross-sectional area between three models are all found to be minor. In addition, the Short model takes the least amount of computing time of the three models (11h compared to 21 h for Long and 19 h for Moderate). The present results indicate that the use of short elastic upstream artery can shorten the time required for pati ent-specific FSI simulations without impacting the overall accuracy of the results.
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Affiliation(s)
- C J Lee
- The Australian School of Advanced Medicine, Macquarie University, Sydney, Australia
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12
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Sadasivan C, Fiorella DJ, Woo HH, Lieber BB. Physical factors effecting cerebral aneurysm pathophysiology. Ann Biomed Eng 2013; 41:1347-65. [PMID: 23549899 DOI: 10.1007/s10439-013-0800-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 03/21/2013] [Indexed: 12/21/2022]
Abstract
Many factors that are either blood-, wall-, or hemodynamics-borne have been associated with the initiation, growth, and rupture of intracranial aneurysms. The distribution of cerebral aneurysms around the bifurcations of the circle of Willis has provided the impetus for numerous studies trying to link hemodynamic factors (flow impingement, pressure, and/or wall shear stress) to aneurysm pathophysiology. The focus of this review is to provide a broad overview of such hemodynamic associations as well as the subsumed aspects of vascular anatomy and wall structure. Hemodynamic factors seem to be correlated to the distribution of aneurysms on the intracranial arterial tree and complex, slow flow patterns seem to be associated with aneurysm growth and rupture. However, both the prevalence of aneurysms in the general population and the incidence of ruptures in the aneurysm population are extremely low. This suggests that hemodynamic factors and purely mechanical explanations by themselves may serve as necessary, but never as necessary and sufficient conditions of this disease's causation. The ultimate cause is not yet known, but it is likely an additive or multiplicative effect of a handful of biochemical and biomechanical factors.
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Affiliation(s)
- Chander Sadasivan
- Department of Neurological Surgery, Stony Brook University Medical Center, 100 Nicolls Road, HSC T12, Room 080, Stony Brook, NY 11794-8122, USA
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13
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Tang AYS, Chan HN, Tsang ACO, Leung GKK, Leung KM, Yu ACH, Chow KW. The effects of stent porosity on the endovascular treatment of intracranial aneurysms located near a bifurcation. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/jbise.2013.68099] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Contribution of the hemodynamics of A1 dysplasia or hypoplasia to anterior communicating artery aneurysms: a 3-dimensional numerical simulation study. J Comput Assist Tomogr 2012; 36:421-6. [PMID: 22805671 DOI: 10.1097/rct.0b013e3182574dea] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To explore the association between the hemodynamics and formation, growth, and rupture of aneurysms in anterior communicating arteries (ACoA) with A1 dysplasia or hypoplasia. METHODS A series of 3-dimensional numerical simulation models of the anterior communicating artery complex (ACoAC) were designed geometrically. The diameter of A1 was fixed on one side and decreased gradually on the other side. Three groups of ACoA aneurysm model growth were constructed with different positions to the dominant bifurcation. Blood flow was modeled as an incompressible Newtonian fluid described by the unsteady Navier-Stokes equations. Vessel walls were assumed to be rigid; no slip boundary conditions were applied at the walls. RESULTS Wall shear stress (WSS), flow velocity, and pressure were influenced by the dynamic variations of A1 diameter. When the diameter of the nondominant A1 gradually decreased, WSS and flow velocity dynamically increased in the dominant bifurcation and pressure decreased. Wall shear stress differences were significant between the dominant and nondominant bifurcations (t = 6.543; P < 0.05). With aneurysm growth, WSS and flow velocity gradually decreased, and turbulence appeared. Wall shear stress was lower at the bifurcation than that 0.02 mm and 0.1 mm to the bifurcation, whereas flow velocity and turbulent flow were more obvious. CONCLUSIONS A1 dysplasia/hypoplasia is a potential risk factor in the formation of ACoA aneurysms. Wall shear stress increase may contribute to aneurysm formation. Wall shear stress decrease and turbulent flow may be responsible for the growth and rupture of ACoA aneurysms. The hemodynamic mechanism in the growth and rupture of aneurysms in different locations might be different.
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Seshadhri S, Janiga G, Beuing O, Skalej M, Thévenin D. Impact of stents and flow diverters on hemodynamics in idealized aneurysm models. J Biomech Eng 2011; 133:071005. [PMID: 21823744 DOI: 10.1115/1.4004410] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cerebral aneurysms constitute a major medical challenge as treatment options are limited and often associated with high risks. Statistically, up to 3% of patients with a brain aneurysm may suffer from bleeding for each year of life. Eight percent of all strokes are caused by ruptured aneurysms. In order to prevent this rupture, endovascular stenting using so called flow diverters is increasingly being regarded as an alternative to the established coil occlusion method in minimally invasive treatment. Covering the neck of an aneurysm with a flow diverter has the potential to alter the hemodynamics in such a way as to induce thrombosis within the aneurysm sac, stopping its further growth, preventing its rupture and possibly leading to complete resorption. In the present study the influence of different flow diverters is quantified considering idealized patient configurations, with a spherical sidewall aneurysm placed on either a straight or a curved parent vessel. All important hemodynamic parameters (exchange flow rate, velocity, and wall shear stress) are determined in a quantitative and accurate manner using computational fluid dynamics when varying the key geometrical properties of the aneurysm. All simulations are carried out using an incompressible, Newtonian fluid with steady conditions. As a whole, 72 different cases have been considered in this systematic study. In this manner, it becomes possible to compare the efficiency of different stents and flow diverters as a function of wire density and thickness. The results show that the intra-aneurysmal flow velocity, wall shear stress, mean velocity, and vortex topology can be considerably modified thanks to insertion of a suitable implant. Intra-aneurysmal residence time is found to increase rapidly with decreasing stent porosity. Of the three different implants considered in this study, the one with the highest wire density shows the highest increase of intra-aneurysmal residence time for both the straight and the curved parent vessels. The best hemodynamic modifications are always obtained for a small aneurysm diameter.
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Affiliation(s)
- Santhosh Seshadhri
- Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg Otto von Guericke, Universitätsplatz 2, D-39106 Magdeburg, Germany.
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Mapping vascular response to in vivo Hemodynamics: application to increased flow at the basilar terminus. Biomech Model Mechanobiol 2010; 9:421-34. [DOI: 10.1007/s10237-009-0185-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Accepted: 12/21/2009] [Indexed: 10/20/2022]
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17
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Ateshian GA, Friedman MH. Integrative biomechanics: A paradigm for clinical applications of fundamental mechanics. J Biomech 2009; 42:1444-1451. [DOI: 10.1016/j.jbiomech.2009.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 03/27/2009] [Accepted: 04/04/2009] [Indexed: 11/26/2022]
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Ohshima T, Miyachi S, Hattori KI, Takahashi I, Ishii K, Izumi T, Yoshida J. Risk of aneurysmal rupture: the importance of neck orifice positioning-assessment using computational flow simulation. Neurosurgery 2008; 62:767-73; discussion 773-5. [PMID: 18496182 DOI: 10.1227/01.neu.0000318160.59848.46] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE The aim of the present study was to clarify the risk of rupture in terminal-type intracranial aneurysms using computational flow simulation analysis. METHODS First, idealized three-dimensional aneurysmal models were built from a solid voxel on the computer. We focused on round terminal-type aneurysms with the positioning of the neck orifice set according to the following three patterns in relationship to the axis of the parent artery: the Type-A neck orifice was positioned directly in line with the flow of the parent artery; the Type-B neck orifice was shifted 1.5 mm offline toward the unilateral branch; and the Type-C neck orifice was shifted 3 mm offline. Computational flow simulations were applied with Fujitsu alpha-Flow software (Fujitusu, Tokyo, Japan). We analyzed flow patterns using modified patient-specific models. We also investigated actual clinical situations to evaluate the differences in neck-orifice positioning between 20 ruptured aneurysms and 26 unruptured ones using three-dimensional angiograms. RESULTS The Type-A neck orifice showed completely symmetrical stream lines in the aneurysm, whereas the Type-C orifice showed a clear round circulation. The Type-B neck orifice, on the other hand, exhibited intra-aneurysmal flow separation. The clinical research demonstrated that Type-B aneurysms were more likely to be found in the ruptured group (P < 0.05). CONCLUSION Flow separation, recognized as one of the causes of intimal injury, could be observed only in Type-B aneurysms, a result that corresponded well with our clinical experience. From the flow-dynamics point of view, this positioning of the neck orifice may be one of the risk factors most likely to induce the rupture of unruptured aneurysms.
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Affiliation(s)
- Tomotaka Ohshima
- Department of Neurosurgery, Nagoya University Graduate School of Medicine, Nagoya, Japan
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19
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Comparison of two stents in modifying cerebral aneurysm hemodynamics. Ann Biomed Eng 2008; 36:726-41. [PMID: 18264766 DOI: 10.1007/s10439-008-9449-4] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 10/24/2007] [Indexed: 02/02/2023]
Abstract
There is a general lack of quantitative understanding about how specific design features of endovascular stents (struts and mesh design, porosity) affect the hemodynamics in intracranial aneurysms. To shed light on this issue, we studied two commercial high-porosity stents (Tristar stent and Wallstent) in aneurysm models of varying vessel curvature as well as in a patient-specific model using Computational Fluid Dynamics. We investigated how these stents modify hemodynamic parameters such as aneurysmal inflow rate, stasis, and wall shear stress, and how such changes are related to the specific designs. We found that the flow damping effect of stents and resulting aneurysmal stasis and wall shear stress are strongly influenced by stent porosity, strut design, and mesh hole shape. We also confirmed that the damping effect is significantly reduced at higher vessel curvatures, which indicates limited usefulness of high-porosity stents as a stand-alone treatment. Finally, we showed that the stasis-inducing performance of stents in 3D geometries can be predicted from the hydraulic resistance of their flat mesh screens. From this, we propose a methodology to cost-effectively compare different stent designs before running a full 3D simulation.
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Hirabayashi M, Ohta M, Rüfenacht DA, Chopard B. Characterization of flow reduction properties in an aneurysm due to a stent. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2003; 68:021918. [PMID: 14525017 DOI: 10.1103/physreve.68.021918] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2003] [Indexed: 05/24/2023]
Abstract
We consider a lattice Boltzmann simulation of blood flow in a vessel deformed by the presence of an aneurysm. Modern clinical treatments involve introducing a stent (a tubular mesh of wires) into the cerebral artery in order to reduce the flow inside the aneurysm and favor its spontaneous reabsorption. A crucial question is to design the stent with suitable porosity so as to produce the most effective flow reduction. We propose a stent positioning factor as a characterizing tool for stent pore design in order to describe the flow reduction effect and reveal the several flow reduction mechanisms using this effect.
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Affiliation(s)
- Miki Hirabayashi
- CUI, Department d'Informatique, University of Geneva, 24 rue du General-Dufour, CH-1211 Geneva 4, Switzerland
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21
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Lattice Boltzmann Analysis of the Flow Reduction Mechanism in Stented Cerebral Aneurysms for the Endovascular Treatment. ACTA ACUST UNITED AC 2003. [DOI: 10.1007/3-540-44860-8_108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Ujiie H, Tachibana H, Hiramatsu O, Hazel AL, Matsumoto T, Ogasawara Y, Nakajima H, Hori T, Takakura K, Kajiya F. Effects of size and shape (aspect ratio) on the hemodynamics of saccular aneurysms: a possible index for surgical treatment of intracranial aneurysms. Neurosurgery 1999; 45:119-29; discussion 129-30. [PMID: 10414574 DOI: 10.1097/00006123-199907000-00028] [Citation(s) in RCA: 189] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
OBJECTIVE The present study was undertaken to explore the relationship between the characteristic geometry of aneurysms prone to rupture and the blood flow patterns therein, using microsurgically produced aneurysms that simulated human middle cerebral artery aneurysms in scale and shape. METHODS We measured in vivo velocity profiles using our 20-MHz, 80-channel, Doppler ultrasound velocimeter. We produced small (< or =5 mm, 5 cases) and large (6-13 mm, 12 cases) aneurysms with round, dumbbell, or multilobular shapes. RESULTS The fundamental patterns of intra-aneurysmal flow were composed of inflow, circulating flow, and outflow. The inflow, which entered the aneurysm only during the systolic phase, was strongly influenced by the position and size of the neck and the flow ratio into the distal branches. The outflow was usually nonpulsatile and of low velocity. The circulating flow depended on the aspect ratio (depth/neck width). A single recirculation zone was observed in aneurysms with aspect ratios of less than 1.6. This circulation did not seem to extend to areas with aspect ratios greater than this value; in aneurysms with aspect ratios of more than 1.6, a much slower circulation was observed near the dome. Furthermore, in the dome of dumbbell-shaped aneurysms and daughter aneurysms, no flow was detected. Intra-aneurysmal flow was determined by the aspect ratio, rather than the aneurysm size. CONCLUSION The localized, extremely low-flow condition that was observed in the dome of aneurysms with aspect ratios of more than 1.6 is a common flow characteristic in the geometry of ruptured aneurysms, so great care should be taken for patients with unruptured intracranial aneurysms with aspect ratios of more than 1.6.
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Affiliation(s)
- H Ujiie
- Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, Japan
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Ujiie H, Tachibana H, Hiramatsu O, Hazel AL, Matsumoto T, Ogasawara Y, Nakajima H, Hori T, Takakura K, Kajiya F. Effects of Size and Shape (Aspect Ratio) on the Hemodynamics of Saccular Aneurysms: A Possible Index for Surgical Treatment of Intracranial Aneurysms. Neurosurgery 1999. [DOI: 10.1227/00006123-199907000-00028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Aenis M, Stancampiano AP, Wakhloo AK, Lieber BB. Modeling of flow in a straight stented and nonstented side wall aneurysm model. J Biomech Eng 1997; 119:206-12. [PMID: 9168397 DOI: 10.1115/1.2796081] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We investigated the changes of flow patterns in a blood vessel with a side wall aneurysm resulting from placement of a stent. Local hemodynamics can be markedly altered by placing an intravascular stent, which covers the orifice of the aneurysm. The alternations in flow patterns can lead to flow stasis in the aneurysmal pouch and promote the formation of a stable thrombus. Furthermore, a porous stent can serve as substrate for neointimal growth and subsequently induce a remodeling of the diseased arterial segment. To examine changes in local hemodynamics due to stent placement, a stented and nonstented aneurysm model was investigated computationally in a three-dimensional configuration using a finite element fluid dynamics program. The finite element model was studied under incompressible, pulsatile, viscous, Newtonian conditions. The fluid dynamic similarity parameter, i.e., the maximum/minimum Reynolds number, was set at about 240/25 based on cross-sectional average instantaneous flow. The Womersley number was set to 2.5. These values are representative of large cerebral arteries. The results of the stented versus the nonstented model show substantial difference sin flow patterns inside the aneurysmal pouch. Flow activity inside the stented aneurysm model is significantly diminished and flow inside the parent vessel is less undulated and is directed past the orifice. A high-pressure zone at the distal neck and the dome of the aneurysm prior to stenting decreases after stent placement. However, elevated pressure values are found at the stent filaments facing the current. Higher shear rates are observed at the distal aneurysmal neck after stenting, but are confined to a smaller region and are unidirectional compared to the nonstented model.
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Affiliation(s)
- M Aenis
- Department of Mechanical and Aerospace Engineering, State University of New York at Buffalo 14260, USA
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Magnetic Resonance Imaging zur Erfassung von Blutflussprofilen in Gefässen des menschlichen Körpers. BIOMED ENG-BIOMED TE 1993. [DOI: 10.1515/bmte.1993.38.s1.359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Boesiger P, Maier SE, Kecheng L, Scheidegger MB, Meier D. Visualization and quantification of the human blood flow by magnetic resonance imaging. J Biomech 1992; 25:55-67. [PMID: 1733984 DOI: 10.1016/0021-9290(92)90245-v] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Magnetic Resonance Imaging (MRI) offers new possibilities for the visualization and the noninvasive quantification of the blood flow in human vessels. By the application of conventional gradient echo sequences with electrocardiographic gating on a 1.5 Tesla whole body MRI system the flow induced phase shifts in the ascending and the abdominal aorta are analyzed. The instantaneous two-dimensional velocity profiles and the instantaneous flow rates are determined in a series of subsequent images with high temporal resolution throughout the cardiac cycle. For the flow analysis in further vessels and for the analysis of more complex flow patterns, as they occur in bifurcations or stenoses, a new MR flow imaging technique called FAcE with extremely short echo times is introduced and the first results of flow examinations in a bifurcation phantom and in the carotid artery are presented.
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Affiliation(s)
- P Boesiger
- Institute of Biomedical Engineering and Medical Informatics, University of Zurich, Switzerland
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