scholarly journals Effect of Pulsatility on the Transport of Thrombin in an Idealized Cerebral Aneurysm Geometry

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 133
Author(s):  
Struan Hume ◽  
Jean-Marc Ilunga Tshimanga ◽  
Patrick Geoghegan ◽  
Arnaud G. Malan ◽  
Wei Hua Ho ◽  
...  
Keyword(s):  
Computational Model ◽  
Steady Flow ◽  
Cerebral Aneurysm ◽  
Computational Models ◽  
Cerebral Aneurysms ◽  
Scalar Function ◽  
Aneurysm Wall ◽  
Aneurysm Thrombosis ◽  
Using Data

Computational models of cerebral aneurysm thrombosis are designed for use in research and clinical applications. A steady flow assumption is applied in many of these models. To explore the accuracy of this assumption a pulsatile-flow thrombin-transport computational fluid dynamics (CFD) model, which uses a symmetrical idealized aneurysm geometry, was developed. First, a steady-flow computational model was developed and validated using data from an in vitro experiment, based on particle image velocimetry (PIV). The experimental data revealed an asymmetric flow pattern in the aneurysm. The validated computational model was subsequently altered to incorporate pulsatility, by applying a data-derived flow function at the inlet boundary. For both the steady and pulsatile computational models, a scalar function simulating thrombin generation was applied at the aneurysm wall. To determine the influence of pulsatility on thrombin transport, the outputs of the steady model were compared to the outputs of the pulsatile model. The comparison revealed that in the pulsatile case, an average of 10.2% less thrombin accumulates within the aneurysm than the steady case for any given time, due to periodic losses of a significant amount of thrombin-concentrated blood from the aneurysm into the parent vessel’s bloodstream. These findings demonstrate that pulsatility may change clotting outcomes in cerebral aneurysms.

scholarly journals Thrombin–Fibrinogen In Vitro Flow Model of Thrombus Growth in Cerebral Aneurysms

TH Open ◽  
2021 ◽  
Vol 05 (02) ◽  
pp. e155-e162
Author(s):  
Malebogo N. Ngoepe ◽  
Etheresia Pretorius ◽  
Ilunga J. Tshimanga ◽  
Zahra Shaikh ◽  
Yiannis Ventikos ◽  
...  
Keyword(s):  
Cerebral Aneurysm ◽  
Computational Models ◽  
Flow Model ◽  
Three Dimensional ◽  
Significant Risk ◽  
Cerebral Aneurysms ◽  
Parent Vessel ◽  
Risk Of Rupture ◽  
Aneurysm Thrombosis

AbstractCerebral aneurysms are balloon-like structures that develop on weakened areas of cerebral artery walls, with a significant risk of rupture. Thrombi formation is closely associated with cerebral aneurysms and has been observed both before and after intervention, leading to a wide variability of outcomes in patients with the condition. The attempt to manage the outcomes has led to the development of various computational models of cerebral aneurysm thrombosis. In the current study, we developed a simplified thrombin–fibrinogen flow system, based on commercially available purified human-derived plasma proteins, which enables thrombus growth and tracking in an idealized cerebral aneurysm geometry. A three-dimensional printed geometry of an idealized cerebral aneurysm and parent vessel configuration was developed. An unexpected outcome was that this phantom-based flow model allowed us to track clot growth over a period of time, by using optical imaging to record the progression of the growing clot into the flow field. Image processing techniques were subsequently used to extract important quantitative metrics from the imaging dataset, such as end point intracranial thrombus volume. The model clearly demonstrates that clot formation, in cerebral aneurysms, is a complex interplay between mechanics and biochemistry. This system is beneficial for verifying computational models of cerebral aneurysm thrombosis, particularly those focusing on initial angiographic occlusion outcomes, and will also assist manufacturers in optimizing interventional device designs.

Electrophysiological characterization and computational models of HVC neurons in the zebra finch

2013 ◽  
Vol 110 (5) ◽  
pp. 1227-1245 ◽  
Author(s):  
Arij Daou ◽  
Matthew T. Ross ◽  
Frank Johnson ◽  
Richard L. Hyson ◽  
Richard Bertram
Keyword(s):  
Computational Models ◽  
Premotor Cortex ◽  
Brain Slices ◽  
Ionic Currents ◽  
Proper Name ◽  
Using Data ◽  
Electrophysiological Characterization

The nucleus HVC (proper name) within the avian analog of mammal premotor cortex produces stereotyped instructions through the motor pathway leading to precise, learned vocalization by songbirds. Electrophysiological characterization of component HVC neurons is an important requirement in building a model to understand HVC function. The HVC contains three neural populations: neurons that project to the RA (robust nucleus of arcopallium), neurons that project to Area X (of the avian basal ganglia), and interneurons. These three populations are interconnected with specific patterns of excitatory and inhibitory connectivity, and they fire with characteristic patterns both in vivo and in vitro. We performed whole cell current-clamp recordings on HVC neurons within brain slices to examine their intrinsic firing properties and determine which ionic currents are responsible for their characteristic firing patterns. We also developed conductance-based models for the different neurons and calibrated the models using data from our brain slice work. These models were then used to generate predictions about the makeup of the ionic currents that are responsible for the different responses to stimuli. These predictions were then tested and verified in the slice using pharmacological manipulations. The model and the slice work highlight roles of a hyperpolarization-activated inward current ( Ih), a low-threshold T-type Ca2+ current ( ICa-T), an A-type K+ current ( IA), a Ca2+-activated K+ current ( ISK), and a Na+-dependent K+ current ( IKNa) in driving the characteristic neural patterns observed in the three HVC neuronal populations. The result is an improved characterization of the HVC neurons responsible for song production in the songbird.

A Mechanistic Motor-Clutch Model That Explains Cell Shape Dynamics to Cyclic Stretch

2022 ◽  
Author(s):  
Benjamin W. Scandling ◽  
Jia Gou ◽  
Jessica Thomas ◽  
Jacqueline Xuan ◽  
Chuan Xue ◽  
...  
Keyword(s):  
Computational Model ◽  
Computational Models ◽  
The Body ◽  
Cyclic Stretch ◽  
Substrate Stiffness ◽  
Cell Alignment ◽  
Cellular Mechanisms ◽  
Actin Bundles ◽  
The Impact

Many cells in the body experience cyclic mechanical loading, which can impact cellular processes and morphology. In vitro studies often report that cells reorient in response to cyclic stretch of their substrate. To explore cellular mechanisms involved in this reorientation, a computational model was developed by utilizing the previous computational models of the actin-myosin-integrin motor-clutch system developed by others. The computational model predicts that under most conditions, actin bundles align perpendicular to the direction of applied cyclic stretch, but under specific conditions, such as low substrate stiffness, actin bundles align parallel to the direction of stretch. The model also predicts that stretch frequency impacts the rate of reorientation, and that proper myosin function is critical in the reorientation response. These computational predictions are consistent with reports from the literature and new experimental results presented here. The model suggests that the impact of different stretching conditions (stretch type, amplitude, frequency, substrate stiffness, etc.) on the direction of cell alignment can largely be understood by considering their impact on cell-substrate detachment events, specifically whether detachment occurs during stretching or relaxing of the substrate.

Modeling the Geometry, Hemodynamics and Tissue Mechanics of Cerebral Aneurysms

2004 ◽  
Author(s):  
Baoshun Ma ◽  
Robert Harbaugh ◽  
Jia Lu ◽  
Madhavan Raghavan
Keyword(s):  
Shear Stress ◽  
Mechanical Stress ◽  
Cerebral Aneurysm ◽  
Residence Time ◽  
Cerebral Aneurysms ◽  
Lesion Size ◽  
Tissue Mechanics ◽  
Particle Residence Time ◽  
Aneurysm Wall ◽  
Geometric Size

The relationship between cerebral aneurysm geometry and biomechanics was investigated. Human cerebral aneurysm geometry was reconstructed from computed tomography angiography (CTA) and refined. Various indices of global geometric (size and shape) features were computed based on differential and computational geometry techniques. Computational fluid dynamics (CFD) simulations were performed to model both steady and pulsatile blood flow in the aneurysm and surrounding vasculature. Hemodynamic indices such as wall shear stress, pressure and particle residence time were obtained. Nonlinear finite element method (FEM) and a reported finite strain constitutive model were employed to estimate the distribution of mechanical stress in the aneurysm wall under static pressure. Shear stress, sac pressure and mechanical stress correlated better with lesion shape while particle residence time correlated better with lesion size.

Evaluation of Cerebral Aneurysm Stent Performance in a Subject-Specific Computational Model

2010 ◽  
Author(s):  
Timothy J. Gundert ◽  
John F. LaDisa
Keyword(s):  
United States ◽  
Blood Flow ◽  
Computational Model ◽  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
The United States ◽  
Flow Stagnation ◽  
Subject Specific ◽  
Endovascular Devices ◽  
Saccular Aneurysms

Rupture of cerebral aneurysms is the second leading cause of stroke in the United States [1]. Altered hemodynamics is thought to play a role in the progression and subsequent rupture of aneurysms. Blood flow into an aneurysm can be occluded by surgically clipping the aneurysm or using endovascular devices, such as stents or coils. In saccular aneurysms, coiling alone may be a sufficient method of inducing flow stagnation in the aneurysm, causing thrombosis and preventing rupture. When treating wide-necked aneurysms, stenting is often used in conjunction with coiling to prevent the migration of coils. Many investigators have studied the ability of a stent-only treatment to favorably alter flow in aneurysms [2, 3].

scholarly journals A Computational Model for Cardiomyocytes Mechano-Electric Stimulation to Enhance Cardiac Tissue Regeneration

Mathematics ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1875
Author(s):  
Pau Urdeitx ◽  
Mohamed H. Doweidar
Keyword(s):  
Extracellular Matrix ◽  
Computational Model ◽  
Electric Fields ◽  
Electric Stimulation ◽  
Computational Models ◽  
Cell Maturation ◽  
Cardiac Cell ◽  
Cell Orientation ◽  
Aspect Ratios

Electrical and mechanical stimulations play a key role in cell biological processes, being essential in processes such as cardiac cell maturation, proliferation, migration, alignment, attachment, and organization of the contractile machinery. However, the mechanisms that trigger these processes are still elusive. The coupling of mechanical and electrical stimuli makes it difficult to abstract conclusions. In this sense, computational models can establish parametric assays with a low economic and time cost to determine the optimal conditions of in-vitro experiments. Here, a computational model has been developed, using the finite element method, to study cardiac cell maturation, proliferation, migration, alignment, and organization in 3D matrices, under mechano-electric stimulation. Different types of electric fields (continuous, pulsating, and alternating) in an intensity range of 50–350 Vm−1, and extracellular matrix with stiffnesses in the range of 10–40 kPa, are studied. In these experiments, the group’s morphology and cell orientation are compared to define the best conditions for cell culture. The obtained results are qualitatively consistent with the bibliography. The electric field orientates the cells and stimulates the formation of elongated groups. Group lengthening is observed when applying higher electric fields in lower stiffness extracellular matrix. Groups with higher aspect ratios can be obtained by electrical stimulation, with better results for alternating electric fields.

A Theoretical Model for Saccular Cerebral Aneurysm Growth: Deformation and Stress Analysis

2007 ◽  
Author(s):  
Martin Kroon ◽  
Gerhard Holzapfel
Keyword(s):  
Cerebral Aneurysm ◽  
Cerebral Aneurysms ◽  
Structural Features ◽  
Constitutive Behavior ◽  
Patient Specific ◽  
Western World ◽  
Specific Information ◽  
Aneurysm Wall ◽  
Aneurysm Growth ◽  
Size Criterion

Aneurysms are abnormal dilatations of arteries, and these lesions are found almost exclusively in humans. Saccular cerebral aneurysms occur most frequently in the Circle of Willis, which is a circuit of arteries supplying the brain with blood. Aneurysms of this kind appear in a few percent of the human population in the Western world. Only a few percent of these lesions do actually rupture, but once rupture occurs the consequences are severe, often with death as outcome. Once a cerebral aneurysm is detected, clinicians need to decide whether operation is required or not. These decisions are mainly based on the size of the aneurysm, where larger aneurysms are considered to be more critical than smaller ones. This size criterion is, however, not very reliable, and criteria based on mechanical fields (stress or strain) of the aneurysm should be taken into account in the decision. This, however, requires knowledge of the constitutive behavior of the aneurysm wall, together with patient-specific information regarding geometry and boundary conditions. In order to be able to model the constitutive behavior of an aneurysm, the structural features of the aneurysm wall need to be determined. Knowledge of the etiology of the aneurysm may here provide important insights.

scholarly journals Navigation of a magnetic micro-robot through a cerebral aneurysm phantom with magnetic particle imaging

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anna C. Bakenecker ◽  
Anselm von Gladiss ◽  
Hannes Schwenke ◽  
André Behrends ◽  
Thomas Friedrich ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Cerebral Aneurysm ◽  
Magnetic Particle ◽  
Cerebral Aneurysms ◽  
Localization Accuracy ◽  
Magnetic Particle Imaging ◽  
Micro Robot ◽  
Life Threatening ◽  
Particle Imaging

AbstractCerebral aneurysms are potentially life threatening and nowadays treated by a catheter-guided coiling or by a neurosurgical clipping intervention. Here, we propose a helically shaped magnetic micro-robot, which can be steered by magnetic fields in an untethered manner and could be applied for a novel coiling procedure. This is shown by navigating the micro-robot through an additively manufactured phantom of a human cerebral aneurysm. The magnetic fields are applied with a magnetic particle imaging (MPI) scanner, which allows for the navigation and tomographic visualization by the same machine. With MPI the actuation process can be visualized with a localization accuracy of 0.68 mm and an angiogram can be acquired both without any radiation exposure. First in-vitro phantom experiments are presented, showing an idea of a robot conducted treatment of cerebral aneurysms.

Quantitative Effects of Coil Packing Density on Cerebral Aneurysm Fluid Dynamics: An In Vitro Steady Flow Study

2010 ◽  
Vol 38 (7) ◽  
pp. 2293-2301 ◽  
Author(s):  
M. Haithem Babiker ◽  
L. Fernando Gonzalez ◽  
Felipe Albuquerque ◽  
Daniel Collins ◽  
Arius Elvikis ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Steady Flow ◽  
Cerebral Aneurysm ◽  
Packing Density ◽  
Flow Study

scholarly journals Expression of NF-κB, MCP-1 and MMP-9 in a Cerebral Aneurysm Rabbit Model

2014 ◽  
Vol 41 (2) ◽  
pp. 200-205 ◽  
Author(s):  
Yan fei Liu ◽  
Yongqiang Zhang ◽  
Dawei Dai ◽  
Zheng Xu
Keyword(s):  
Cerebral Aneurysm ◽  
Elastic Fiber ◽  
Rabbit Model ◽  
Smooth Muscles ◽  
Cerebral Aneurysms ◽  
Inflammatory Cells ◽  
Elastic Fibers ◽  
Control Group ◽  
Brain Aneurysm ◽  
Aneurysm Wall

Objective:We explored the early expression of NF-κB, MCP-1 and -MMP 9 in a rabbit carotid aneurysm model, and investigated the possible mechanism of aneurysm.Methods:twenty four adult new Zealand rabbits were divided into four groups. normal control (group a); rabbits received elastase induction for 1, 2 3 weeks (group b, C and d respectively); hematoxylin-eosin stains were performed for observation. the mrna and protein expression of NF-κB, MCP-1 and MMP-9 were analyzed using RT-PCR and immunohistochemical methods.Results:the expression of NF-κB and MCp-1 reached their peaks after induction for one week, then decreased. their expression in week 1 and week 2 had no statistical difference. the expression of MMP-9 increased after induction. We observed the highest expression at week 3. as the induction time increased, the number of smooth muscles reduced. endothelial cells were damaged; the aneurysm wall elastic layer was damaged.Conclusion:activation of NF-κB may be one of the initiating factors contributing to the occurrence and development of cerebral aneurysm. MCP-1 induced macrophage adhesion and infiltration in the artery wall of cerebral aneurysms, and contributed to the occurrence and development of brain aneurysm. damage to elastic fibers is one of the key factors for aneurysm formation. increased infiltration of inflammatory cells and the secretion of MMP-9 are the main reasons for elastic fiber damage.

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