scholarly journals A spatio-temporal model for spontaneous thrombus formation in cerebral aneurysms

2015 ◽  
Author(s):  
Orestis Malaspinas ◽  
Alexis Turjman ◽  
Daniel Ribeiro de Sousa ◽  
Guillermo Garcia-Cardena ◽  
Martine Raes ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
In Vitro Experiments ◽  
Cfd Simulations ◽  
Large Space ◽  
Clinical Observations ◽  
Temporal Model ◽  
Spatio Temporal

We propose a new numerical model to describe thrombus formation in cerebral aneurysms. This model combines CFD simulations with a set of bio-mechanical processes identified as being the most important to describe the phenomena at a large space and time scales. The hypotheses of the model are based on in vitro experiments and clinical observations. We document that we can reproduce very well the shape and volume of patient specific thrombus segmented in giant aneurysms.

scholarly journals A spatio-temporal model for spontaneous thrombus formation in cerebral aneurysms

2016 ◽  
Vol 394 ◽  
pp. 68-76 ◽  
Author(s):  
O. Malaspinas ◽  
A. Turjman ◽  
D. Ribeiro de Sousa ◽  
G. Garcia-Cardena ◽  
M. Raes ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Cerebral Aneurysms ◽  
Temporal Model ◽  
Spatio Temporal

Lagrangian Trajectory Simulation of Platelets and Synchrotron Microtomography Augment Hemodynamic Analysis of Intracranial Aneurysms Treated With Embolic Coils

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
Venkat Keshav Chivukula ◽  
Laurel Marsh ◽  
Fanette Chassagne ◽  
Michael C. Barbour ◽  
Cory M. Kelly ◽  
...  
Keyword(s):  
Shear Stress ◽  
Treatment Outcomes ◽  
Intracranial Aneurysms ◽  
Thrombus Formation ◽  
Vascular Wall ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Embolic Coils ◽  
Endovascular Coils

Abstract As frequency of endovascular treatments for intracranial aneurysms increases, there is a growing need to understand the mechanisms for coil embolization failure. Computational fluid dynamics (CFD) modeling often simplifies modeling the endovascular coils as a homogeneous porous medium (PM), and focuses on the vascular wall endothelium, not considering the biomechanical environment of platelets. These assumptions limit the accuracy of computations for treatment predictions. We present a rigorous analysis using X-ray microtomographic imaging of the coils and a combination of Lagrangian (platelet) and Eulerian (endothelium) metrics. Four patient-specific, anatomically accurate in vitro flow phantoms of aneurysms are treated with the same patient-specific endovascular coils. Synchrotron tomography scans of the coil mass morphology are obtained. Aneurysmal hemodynamics are computationally simulated before and after coiling, using patient-specific velocity/pressure measurements. For each patient, we analyze the trajectories of thousands of platelets during several cardiac cycles, and calculate residence times (RTs) and shear exposure, relevant to thrombus formation. We quantify the inconsistencies of the PM approach, comparing them with coil-resolved (CR) simulations, showing the under- or overestimation of key hemodynamic metrics used to predict treatment outcomes. We fully characterize aneurysmal hemodynamics with converged statistics of platelet RT and shear stress history (SH), to augment the traditional wall shear stress (WSS) on the vascular endothelium. Incorporating microtomographic scans of coil morphology into hemodynamic analysis of coiled intracranial aneurysms, and augmenting traditional analysis with Lagrangian platelet metrics improves CFD predictions, and raises the potential for understanding and clinical translation of computational hemodynamics for intracranial aneurysm treatment outcomes.

scholarly journals Computational Fontan Analysis: Preserving accuracy while expediting workflow

2021 ◽  
Author(s):  
Xiaolong Liu ◽  
Seda Aslan ◽  
Byeol Kim ◽  
Linnea Warburton ◽  
Derrick Jackson ◽  
...  
Keyword(s):  
Particle Filtering ◽  
Cfd Simulation ◽  
Fontan Operation ◽  
Flow Distribution ◽  
Mesh Size ◽  
Computational Time ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations

Background: Post-operative outcomes of the Fontan operation have been linked to graft shape after implantation. Computational fluid dynamics (CFD) simulations are used to explore different surgical options. The objective of this study is to perform a systematic in vitro validation for investigating the accuracy and efficiency of CFD simulation to predict Fontan hemodynamics. Methods: CFD simulations were performed to measure indexed power loss (iPL) and hepatic flow distribution (HFD) in 10 patient-specific Fontan models, with varying mesh and numerical solvers. The results were compared with a novel in vitro flow loop setup with 3D printed Fontan models. A high-resolution differential pressure sensor was used to measure the pressure drop for validating iPL predictions. Microparticles with particle filtering system were used to measure HFD. The computational time was measured for a representative Fontan model with different mesh sizes and numerical solvers. Results: When compared to in vitro setup, variations in CFD mesh sizes had significant effect on HFD (p = 0.0002) but no significant impact on iPL (p = 0.069). Numerical solvers had no significant impact in both iPL (p = 0.50) and HFD (P = 0.55). A transient solver with 0.5 mm mesh size requires computational time 100 times more than a steady solver with 2.5 mm mesh size to generate similar results. Conclusions: The predictive value of CFD for Fontan planning can be validated against an in vitro flow loop. The prediction accuracy can be affected by the mesh size, model shape complexity and flow competition.

Abstract WP1: High-Frequency Optical Coherence Tomography for Cerebrovascular Disease

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Ajit S Puri ◽  
Giovanni Ughi ◽  
Robert M King ◽  
Matthew Gounis
Keyword(s):  
Optical Coherence Tomography ◽  
Cerebrovascular Disease ◽  
High Frequency ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Image Resolution ◽  
Patient Specific ◽  
Optical Coherence

Introduction: Optical coherence tomography (OCT) has played an important role in the diagnosis and treatment guidance in coronary artery disease. However, existing OCT systems are not suitable for routine neurovascular applications due to the size and tortuosity of the arteries. Hypothesis: We seek to demonstrate a prototype high-frequency OCT (HF-OCT) capable of high-resolution imaging in simulated cerebrovascular anatomy. Methods: A low-profile HF-OCT system was constructed with an image resolution approaching 10μm. Using an in vitro, patient-specific model of the circle of Willis with circulating porcine blood, we characterized the delivery of the device and ability to image in a tortuous path. Also, human cadaver intracranial atherosclerosis plaques were imaged with HF-OCT and assessed by an expert imager. Finally, neurovascular devices were implanted in 8 pigs (Fig 1) and HF-OCT imaging was compared with gold-standard DSA and CT. Results: In the phantom, optimal blood clearance was achieved through an intermediate catheter (5 Fr Navien) with infusion of contrast at 5 ml/s in the internal carotid and basilar artery, and 3 ml/sec in the MCA. The in vivo study demonstrated that both malapposition of devices or thrombus formation along the device surface could be reliably diagnosed among 3 reviewers (Fleiss’s kappa of 0.87 and 0.9, respectively). This agreement was superior to DSA and CT. Imaging in tortuous swine brachial showed in all cases imaging free of artifacts, uniform illumination and ability to visualize vessel wall layers. Plaque types including ‘lipid pools’, fibrotic, and calcific tissue from cadaver specimens of ICAD could be adequately depicted by HF-OCT. Conclusion: In vitro, in vivo and ex vivo characterization of a novel HF-OCT device has shown it is capable of imaging in the tortuous intracranial vascular anatomy. This technology has to potential to aid in the diagnosis of cerebrovascular disease and guide optimal endovascular treatment.

COMPUTATIONAL INVESTIGATION OF THROMBIN CONCENTRATION IN CEREBRAL ANEURYSMS TREATED WITH FLOW-DIVERTING STENTS

2019 ◽  
Vol 19 (03) ◽  
pp. 1950007
Author(s):  
XUDONG LIU ◽  
YUNHAN CAI ◽  
LUYU SU ◽  
SHENGZHANG WANG ◽  
XINJIAN YANG
Keyword(s):  
Thrombus Formation ◽  
Flow Direction ◽  
Cerebral Aneurysms ◽  
Giant Aneurysm ◽  
Coupling Model ◽  
Patient Specific ◽  
Aneurysm Embolization ◽  
Collateral Artery ◽  
Dynamics Simulations ◽  
Small Aneurysm

Flow-diverting stent is an ongoing embolization device to treat cerebral aneurysms, and it diverts the flow direction to reduce the flow velocity inside the aneurysmal sacs and promote the thrombus formation. However, its effect for aneurysm embolization is controversial. A hemodynamic-biomedical coupling model was constructed to describe the generation and transport of thrombin in arteries, and the model was applied to investigate the variation of thrombin concentration, which plays a key role in thrombus formation, in two patient-specific cerebral aneurysm models when they are treated with Pipeline flow diverting stents. It is observed from computational fluid dynamics simulations that thrombin concentration in the aneurysmal sac without collateral artery increases significantly after Pipeline implantation, however, it has hardly any variation in the aneurysmal sac without collateral artery or in the giant aneurysmal sac after Pipeline implantation. Therefore, we believe that single Pipeline is very effective to embolize a small aneurysm without collateral artery, but cannot embolize a giant aneurysm or a small aneurysm with a collateral artery on its sac effectively.

scholarly journals Vortex Analysis of Intra-Aneurismal Flow in Cerebral Aneurysms

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Kevin Sunderland ◽  
Christopher Haferman ◽  
Gouthami Chintalapani ◽  
Jingfeng Jiang
Keyword(s):  
Vortex Core ◽  
Cardiac Cycle ◽  
Temporal Stability ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Cfd Simulations ◽  
Hemodynamic Characteristics ◽  
Computational Fluid Dynamics Cfd ◽  
Marching Cube Algorithm ◽  
Core Characteristics

This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in “patient-specific” geometries, using computational fluid dynamics (CFD) simulations. Modified versions of knownλ2andQ-criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle. No statistical differences exist in DVO or number of vortex cores between 5 terminal IAs and 5 sidewall IAs. No strong correlation exists between vortex core characteristics and geometric or hemodynamic characteristics of IAs. Statistical independence suggests this proposed method may provide novel IA information. However, threshold values used to determine the vortex core regions and resolution of velocity data influenced analysis outcomes and have to be addressed in future studies. In conclusions, preliminary results show that the proposed methodology may help give novel insight toward aneurismal flow characteristic and help in future risk assessment given more developments.

A CT-Based High-Order Finite Element Analysis of the Human Proximal Femur Compared to In-vitro Experiments

2006 ◽  
Vol 129 (3) ◽  
pp. 297-309 ◽  
Author(s):  
Zohar Yosibash ◽  
Royi Padan ◽  
Leo Joskowicz ◽  
Charles Milgrom
Keyword(s):  
Finite Element ◽  
Proximal Femur ◽  
Mechanical Response ◽  
Clinical Importance ◽  
High Order ◽  
Patient Specific ◽  
In Vitro Experiments ◽  
Element Analysis ◽  
Bone Response

The prediction of patient-specific proximal femur mechanical response to various load conditions is of major clinical importance in orthopaedics. This paper presents a novel, empirically validated high-order finite element method (FEM) for simulating the bone response to loads. A model of the bone geometry was constructed from a quantitative computerized tomography (QCT) scan using smooth surfaces for both the cortical and trabecular regions. Inhomogeneous isotropic elastic properties were assigned to the finite element model using distinct continuous spatial fields for each region. The Young’s modulus was represented as a continuous function computed by a least mean squares method. p-FEMs were used to bound the simulation numerical error and to quantify the modeling assumptions. We validated the FE results with in-vitro experiments on a fresh-frozen femur loaded by a quasi-static force of up to 1500N at four different angles. We measured the vertical displacement and strains at various locations and investigated the sensitivity of the simulation. Good agreement was found for the displacements, and a fair agreement found in the measured strain in some of the locations. The presented study is a first step toward a reliable p-FEM simulation of human femurs based on QCT data for clinical computer aided decision making.

Abstract 1122‐000014: Effects of Patient‐Specific Blood Properties and Inflow Conditions on Hemodynamics in Cerebral Aneurysms

2021 ◽  
Vol 1 (S1) ◽  
Author(s):  
Yuya Uchiyama ◽  
Hiroyuki Takao ◽  
Soichiro Fujimura ◽  
Takashi Suzuki ◽  
Yuma Yamanaka ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Parent Artery ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Visual Evaluation ◽  
The Mean ◽  
Inflow Conditions

Introduction : Computational Fluid Dynamics (CFD) simulation is an effective tool to investigate pathologies and clinical outcomes of cerebral aneurysms from the hemodynamic perspective. However, simulation conditions such as the blood properties and boundary conditions are usually referred to in the literature do not consider patient‐specific values. In this study, we measured blood properties and extracted the inflow conditions from four‐dimensional digital subtraction angiography (4D‐DSA) images for patients who underwent flow diverter (FD) deployment. Then, we conducted CFD simulations considering the deployed FD geometry to investigate the effect of patient‐specific conditions on aneurysmal hemodynamics. Methods : We took whole blood samples of five patients with intracranial aneurysms just before the surgery and measured the blood density and viscosity with a densitometer and a falling needle rheometer. The patients underwent 4D‐DSA imaging, from which we calculated the patient‐specific inflow velocity of each patient using an in‐house flow extraction program. We used in‐house virtual FD deployment software to reproduce the FD geometry for each patient. We then defined the computational domain including the FD geometry. Four CFD simulations were performed for each of the five patients: (1) a steady CFD simulation under a referred Newtonian blood model and previously published inflow conditions as a basic simulation pattern (2) a CFD simulation including the patient‐specific non‐Newtonian blood properties only, (3) a CFD simulation including the inflow conditions only, and (4) a CFD simulation including both the patient‐specific blood properties and inflow conditions. We calculated the mean velocity in the aneurysm normalized by the mean velocity in the parent artery and the wall shear stress (WSS) of the aneurysm. We compared the results of the four CFD simulations and calculated their differences based on the values for the basic simulation pattern. Results : Based on the visual evaluation, the flow structures of the four CFD simulation patterns differed only slightly from each other, but a quantitative comparison revealed that there were large differences in the hemodynamic parameters. For the velocity, there was an average 14.2% difference with the steady CFD simulation results when the patient‐specific blood properties are considered, and an average 35.8% difference when the patient‐specific inflow conditions are considered. There was an average 60.7% difference when both the patient‐specific blood properties and inflow conditions are taken into account. For the WSS, there was an average 8.75% difference when including the patient‐specific blood properties and an average 66.8% difference in including the patient‐specific inflow conditions. There was an average 69.3% difference in including both conditions are considered. It appeared that the effect of including patient‐specific inflow conditions was more substantial than that of including the patient‐specific blood properties, and most robust when both conditions were included. Conclusions : The hemodynamics obtained from CFD simulations with the deployed FD appears to strongly depend on both the blood properties and the inflow conditions. This result implies that CFD simulations with the referred conditions may not accurately reproduce the hemodynamics. It was confirmed that patient‐specific conditions should be included in CFD simulations.

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