Analysis of Hemodynamics and Aneurysm Occlusion after Flow-Diverting Treatment in Rabbit Models (original) (raw)
Related papers
American Journal of Neuroradiology, 2011
BACKGROUND AND PURPOSE: Patient-specific simulations of the hemodynamics in intracranial aneurysms can be constructed by using image-based vascular models and CFD techniques. This work evaluates the impact of the choice of imaging technique on these simulations. MATERIALS AND METHODS: Ten aneurysms, imaged with 3DRA and CTA, were analyzed to assess the reproducibility of geometric and hemodynamic variables across the 2 modalities. RESULTS: Compared with 3DRA models, we found that CTA models often had larger aneurysm necks (P ϭ .05) and that most of the smallest vessels (between 0.7 and 1.0 mm in diameter) could not be reconstructed successfully with CTA. With respect to the values measured in the 3DRA models, the flow rate differed by 14.1 Ϯ 2.8% (mean Ϯ SE) just proximal to the aneurysm and 33.9 Ϯ 7.6% at the aneurysm neck. The mean WSS on the aneurysm differed by 44.2 Ϯ 6.0%. Even when normalized to the parent vessel WSS, a difference of 31.4 Ϯ 9.9% remained, with the normalized WSS in most cases being larger in the CTA model (P ϭ .04). Despite these substantial differences, excellent agreement (Ն 0.9) was found for qualitative variables that describe the flow field, such as the structure of the flow pattern and the flow complexity. CONCLUSIONS: Although relatively large differences were found for all evaluated quantitative hemodynamic variables, the main flow characteristics were reproduced across imaging modalities. ABBREVIATIONS: 3DRA ϭ 3D rotational angiography; ACA ϭ anterior cerebral artery; A N ϭ aneurysm neck area; BA ϭ basilar artery; CFD ϭ computational fluid dynamics; CTA ϭ CT angiography; ⌬ ϭ relative difference between the 3DRA and CTA models with respect to the 3DRA model; ICA ϭ internal carotid artery; LWSS A ϭ the portion of aneurysm wall under low WSS (Ͻ0.4 Pa) at end diastole; M ϭ number of cases for which the value in the CTA model was lower than in the 3DRA model; MCA ϭ middle cerebral artery; MCA M1 ϭ MCA M1 segment; MCA M1-M2 ϭ MCA M1-M2 bifurcation; MWSS A ϭ maximum WSS on the aneurysm wall at peak systole; NQ A ϭ Q A /Q P ; NWSS A ϭ WSS A /WSS P ; N90WSS A ϭ 90WSS A normalized by the mean WSS on the aneurysm at peak systole; OSI ϭ oscillatory shear index; Q A ϭ flow rate into the aneurysm; Q P ϭ flow rate in the parent vessel just proximal to the aneurysm; SE ϭ standard error; VA ϭ vertebral artery; V A ϭ aneurysm volume; 90WSS A ϭ 90th percentile value of the WSS on the aneurysm at peak systole; WSS ϭ wall shear stress; WSS A ϭ mean WSS on the aneurysm wall; WSS P ϭ mean WSS on a segment of the parent vessel just proximal to the aneurysm
Image-Based Computational Simulation of Flow Dynamics in a Giant Intracranial Aneurysm
2003
BACKGROUND AND PURPOSE: Blood flow dynamics are thought to play an important role in the pathogenesis and treatment of intracranial aneurysms; however, hemodynamic quantities of interest are difficult to measure in vivo. This study shows that computational fluid dynamics (CFD) combined with computed rotational angiography can provide such hemodynamic information in a patient-specific and prospective manner.
Novel Methodologies for Investigating the Pathophysiology of Cerebral Aneurysms
2011
An intracranial aneurysm (IA) is a pathological state of a cerebral artery in which the elastin and smooth muscle cells found in the healthy arterial wall are absent. Rupture of an IA is a major cause of subarachnoid hemorrhage. Hemodynamics is believed to play an important role in initiation, development and rupture of the IA. However, the coupling between hemodynamics and aneurysm pathophysiology remains poorly understood. The initiation of cerebral aneurysms is believed to be caused by a breakdown in the homeostatic mechanism of healthy arteries, leading to destructive wall remodeling and damage. Due to its complex nature, there is a need for both controlled in vitro and in vivo studies of IA initiation. We have designed an in vitro flow chamber that can be used to reproduce specific magnitudes of wall shear stress and wall shear stress gradients found at the apices of arterial bifurcations, where aneurysms tend to form. Animal models provide a mechanism for fundamental studies of the coupling between hemodynamics and pathophysiology in cerebral aneurysms. We conducted a sensitivity study to develop an accurate CFD model for an elastase-induced rabbit aneurysm model. We then used this computational model to evaluate the capability of the rabbit model to reproduce hemodynamic features typical of human IAs. Geometric and hemodynamic features of 51 rabbit aneurysm models were analyzed and shown to fall within the range reported for human IAs. This model was also used to study the relationship between aspect ratio and hemodynamics in the v aneurysm sac. An-in silico design‖ approach was then used to explore the possibility of extending the rabbit model to capture more of the flow categories identified in human IAs. Based on a previously developed parametric model for human arterial bifurcations, we created and validated a parametric model for IAs. This parametric model captures important geometric and flow features of both the aneurysm and neighboring vasculature. The model is currently being used for studies of the coupling between geometry and hemodynamics in IAs. It can also be used to guide 3D reconstruction of poor quality clinical data or construct in vitro experimental models. vi TABLE OF CONTENTS
Medical & Biological Engineering & Computing
The purpose of this study is to examine and compare the hemodynamic characteristics of small aneurysms at the same anatomical location. Six internal carotid artery-ophthalmic artery aneurysms smaller than 10 mm were selected. Image-based computational fluid dynamics (CFD) techniques were used to simulate aneurysm hemodynamics. Flow velocity and wall shear stress (WSS) were also quantitatively compared, both in absolute value and relative value using the parent artery as a baseline. We found that flow properties were similar in ruptured and unruptured small aneurysms. However, the WSS was lower at the aneurysm site in unruptured aneurysms and higher in ruptured aneurysms (P < 0.05). Hemodynamic analyses at a single location with similar size enabled us to directly compare the hemodynamics and clinical presentation of brain aneurysms. The results suggest that the WSS in an aneurysm sac can be an important hemodynamic parameter related to the mechanism of brain aneurysm growth and r...
Neurosurgery, 2006
The goal of this study was to use phase-contrast magnetic resonance imaging and computational fluid dynamics to estimate the hemodynamic outcome that might result from different interventional options for treating a patient with a giant fusiform aneurysm. METHODS: We followed a group of patients with giant intracranial aneurysms who have no clear surgical options. One patient demonstrated dramatic aneurysm growth and was selected for further analysis. The aneurysm geometry and input and output flow conditions were measured with contrast-enhanced magnetic resonance angiography and phasecontrast magnetic resonance imaging. The data was imported into a computational fluid dynamics program and the velocity fields and wall shear stress distributions were calculated for the presenting physiological condition and for cases in which the opposing vertebral arteries were either occluded or opened. These models were validated with in vitro flow experiments using a geometrically exact silicone flow phantom. RESULTS: Simulation indicated that altering the flow ratio in the two vertebrals would deflect the main blood jet into the aneurysm belly, and that this would likely reduce the extent of the region of low wall shear stress in the growth zone. CONCLUSIONS: Computational fluid dynamics flow simulations in a complex patient-specific aneurysm geometry were validated by in vivo and in vitro phasecontrast magnetic resonance imaging, and were shown to be useful in modeling the likely hemodynamic impact of interventional treatment of the aneurysm.
Journal of NeuroInterventional Surgery, 2023
Background The novel Contour Neurovascular System (Contour) has been reported to be efficient and safe for the treatment of intracranial, wide-necked bifurcation aneurysms. Flow in the aneurysm and posterior cerebral arteries (PCAs) after Contour deployment has not been analyzed in detail yet. However, this information is crucial for predicting aneurysm treatment outcomes. Methods Time-resolved three-dimensional velocity maps in 14 combinations of patient-based basilar tip aneurysm models with and without Contour devices (sizes between 5 and 14 mm) were analyzed using fourdimensionsal (4D) flow MRI and numerical/image-based flow simulations. A complex virtual processing pipeline was developed to mimic the experimental shape and position of the Contour together with the simulations. Results On average, the Contour significantly reduced intra-aneurysmal flow velocity by 67% (mean w/ = 0.03m/s; mean w/o = 0.12m/s; p-value=0.002), and the time-averaged wall shear stress by more than 87% (mean w/ = 0.17Pa; mean w/o = 1.35Pa; p-value=0.002), as observed both by numerical simulations and 4D flow MRI. Furthermore, a significant reduction in flow (P<0.01) was confirmed by the neck inflow rate, kinetic energy, and inflow concentration index after Contour deployment. Notably, device size has a stronger effect on reducing flow than device positioning. However, positioning affected flow in the PCAs, while being robust in effectively reducing flow. Conclusions This study showed the high efficacy of the Contour device in reducing flow within aneurysms regardless of the exact position. However, we observed an effect on the flow in PCAs, which needs to be investigated further.
Medical & Biological Engineering & Computing, 2008
The purpose of this study is to examine and compare the hemodynamic characteristics of small aneurysms at the same anatomical location. Six internal carotid artery-ophthalmic artery aneurysms smaller than 10 mm were selected. Image-based computational fluid dynamics (CFD) techniques were used to simulate aneurysm hemodynamics. Flow velocity and wall shear stress (WSS) were also quantitatively compared, both in absolute value and relative value using the parent artery as a baseline. We found that flow properties were similar in ruptured and unruptured small aneurysms. However, the WSS was lower at the aneurysm site in unruptured aneurysms and higher in ruptured aneurysms (P \ 0.05). Hemodynamic analyses at a single location with similar size enabled us to directly compare the hemodynamics and clinical presentation of brain aneurysms. The results suggest that the WSS in an aneurysm sac can be an important hemodynamic parameter related to the mechanism of brain aneurysm growth and rupture.
Quantifying the Large-Scale Hemodynamics of Intracranial Aneurysms
American Journal of Neuroradiology, 2014
Hemodynamics play an important role in the mechanisms that govern the initiation, growth, and possible rupture of intracranial aneurysms. The purpose of this study was to objectively characterize these dynamics, classify them, and connect them to aneurysm rupture.