Image-Based CFD Modelling of Hemodynamic Factors in Aneurysm Formation Using a Novel Approach for Digital Removal of Saccular Aneurysms

2009 ◽  
Author(s):  
Matthew D. Ford ◽  
Yiemeng Hoi ◽  
Marina Piccinelli ◽  
Luca Antiga ◽  
David A. Steinman
Keyword(s):  
A Priori ◽  
Patient Specific ◽  
Cfd Modelling ◽  
Specific Location ◽  
Hemodynamic Forces ◽  
Aneurysm Formation ◽  
Novel Approach ◽  
Saccular Aneurysms

Although local hemodynamic forces are widely believed to play a role in aneurysm pathogenesis, the hemodynamic mechanisms have not been confirmed in a prospective manner. Ideally, one would identify the patient-specific vessel that is prone to aneurysm formation and follow it longitudinally to investigate the associated aneurysm formation factors or mechanisms. However, such studies are not practical in humans, and so the knowledge to predict aneurysm formation at a specific location, a priori, is not available.

Influence of Non-Newtonian Models on Simulation of Aneurysm Hemodynamics

2008 ◽  
Author(s):  
Jenn Rossmann ◽  
Carolyn Fisher
Keyword(s):  
Shear Stress ◽  
Aspect Ratio ◽  
Wall Shear Stress ◽  
Flow Patterns ◽  
Aneurysm Rupture ◽  
Patient Specific ◽  
Hemodynamic Forces ◽  
Aneurysm Formation ◽  
Geometric Factors ◽  
Aneurysm Development

Aneurysm rupture rates are often associated with factors such as size, location, and patient specific risks such as age and health. However, the actual physiological causes of the pathogenesis, enlargement, and rupture are unclear. Many studies have shown aneurysm formation to be mechanically mediated. Hemodynamic forces such as wall shear stress (WSS), pressure, and flow patterns have been examined as causes for aneurysm development and eventual rupture [1]. Geometric factors such as the aneurysm size, shape, and aspect ratio may also be important in predicting rupture [2,3].

scholarly journals Wall shear stress gradient is independently associated with middle cerebral artery aneurysm development: a case-control CFD patient-specific study based on 77 patients

BMC Neurology ◽  
2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mikołaj Zimny ◽  
Edyta Kawlewska ◽  
Anna Hebda ◽  
Wojciech Wolański ◽  
Piotr Ładziński ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Case Control ◽  
Independent Effect ◽  
Patient Specific ◽  
Aneurysm Formation ◽  
Wall Shear ◽  
Mca Aneurysm

Abstract Background Previously published computational fluid dynamics (CFD) studies regarding intracranial aneurysm (IA) formation present conflicting results. Our study analysed the involvement of the combination of high wall shear stress (WSS) and a positive WSS gradient (WSSG) in IA formation. Methods We designed a case-control study with a selection of 38 patients with an unruptured middle cerebral artery (MCA) aneurysm and 39 non-aneurysmal controls to determine the involvement of WSS, oscillatory shear index (OSI), the WSSG and its absolute value (absWSSG) in aneurysm formation based on patient-specific CFD simulations using velocity profiles obtained from transcranial colour-coded sonography. Results Among the analysed parameters, only the WSSG had significantly higher values compared to the controls (11.05 vs − 14.76 [Pa/mm], P = 0.020). The WSS, absWSSG and OSI values were not significantly different between the analysed groups. Logistic regression analysis identified WSS and WSSG as significant co-predictors for MCA aneurysm formation, but only the WSSG turned out to be a significant independent prognosticator (OR: 1.009; 95% CI: 1.001–1.017; P = 0.025). Significantly more patients (23/38) in the case group had haemodynamic regions of high WSS combined with a positive WSSG near the bifurcation apex, while in the control group, high WSS was usually accompanied by a negative WSSG (14/39). From the analysis of the ROC curve for WSSG, the area under the curve (AUC) was 0.654, with the optimal cut-off value −0.37 Pa/mm. The largest AUC was recognised for combined WSS and WSSG (AUC = 0.671). Our data confirmed that aneurysms tend to form near the bifurcation apices in regions of high WSS values accompanied by positive WSSG. Conclusions The development of IAs is determined by an independent effect of haemodynamic factors. High WSS impacts MCA aneurysm formation, while a positive WSSG mainly promotes this process.

Mathematical model of the rupture mechanism of intracranial saccular aneurysms through daughter aneurysm formation and growth

2005 ◽  
Vol 27 (5) ◽  
pp. 459-465 ◽  
Author(s):  
Hui Meng ◽  
Yixiang Feng ◽  
Scott H. Woodward ◽  
Bernard R. Bendok ◽  
Ricardo A. Hanel ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Aneurysm Formation ◽  
Rupture Mechanism ◽  
Saccular Aneurysms

scholarly journals A regional CO2 observing system simulation experiment for the ASCENDS satellite mission

2014 ◽  
Vol 14 (23) ◽  
pp. 12897-12914 ◽  
Author(s):  
J. S. Wang ◽  
S. R. Kawa ◽  
J. Eluszkiewicz ◽  
D. F. Baker ◽  
M. Mountain ◽  
...  
Keyword(s):  
Measurement Errors ◽  
Dispersion Model ◽  
A Priori ◽  
Wrf Model ◽  
Particle Dispersion ◽  
Instrument Design ◽  
Satellite Mission ◽  
Model Framework ◽  
Satellite Systems ◽  
Novel Approach

Abstract. Top–down estimates of the spatiotemporal variations in emissions and uptake of CO2 will benefit from the increasing measurement density brought by recent and future additions to the suite of in situ and remote CO2 measurement platforms. In particular, the planned NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) satellite mission will provide greater coverage in cloudy regions, at high latitudes, and at night than passive satellite systems, as well as high precision and accuracy. In a novel approach to quantifying the ability of satellite column measurements to constrain CO2 fluxes, we use a portable library of footprints (surface influence functions) generated by the Stochastic Time-Inverted Lagrangian Transport (STILT) model in combination with the Weather Research and Forecasting (WRF) model in a regional Bayesian synthesis inversion. The regional Lagrangian particle dispersion model framework is well suited to make use of ASCENDS observations to constrain weekly fluxes in North America at a high resolution, in this case at 1° latitude × 1° longitude. We consider random measurement errors only, modeled as a function of the mission and instrument design specifications along with realistic atmospheric and surface conditions. We find that the ASCENDS observations could potentially reduce flux uncertainties substantially at biome and finer scales. At the grid scale and weekly resolution, the largest uncertainty reductions, on the order of 50%, occur where and when there is good coverage by observations with low measurement errors and the a priori uncertainties are large. Uncertainty reductions are smaller for a 1.57 μm candidate wavelength than for a 2.05 μm wavelength, and are smaller for the higher of the two measurement error levels that we consider (1.0 ppm vs. 0.5 ppm clear-sky error at Railroad Valley, Nevada). Uncertainty reductions at the annual biome scale range from ~40% to ~75% across our four instrument design cases and from ~65% to ~85% for the continent as a whole. Tests suggest that the quantitative results are moderately sensitive to assumptions regarding a priori uncertainties and boundary conditions. The a posteriori flux uncertainties we obtain, ranging from 0.01 to 0.06 Pg C yr−1 across the biomes, would meet requirements for improved understanding of long-term carbon sinks suggested by a previous study.

scholarly journals Monitoring distributed computing beyond the traditional time-series histogram

2020 ◽  
Vol 245 ◽  
pp. 03036
Author(s):  
M S Doidge ◽  
P. A. Love ◽  
J Thornton
Keyword(s):  
Time Series ◽  
Distributed Computing ◽  
Real Time ◽  
A Priori ◽  
Time Data ◽  
Use Of Time ◽  
Computing Services ◽  
Monitoring Tools ◽  
Novel Approach ◽  
Current Monitoring

In this work we describe a novel approach to monitor the operation of distributed computing services. Current monitoring tools are dominated by the use of time-series histograms showing the evolution of various metrics. These can quickly overwhelm or confuse the viewer due to the large number of similar looking graphs. We propose a supplementary approach through the sonification of real-time data streamed directly from a variety of distributed computing services. The real-time nature of this method allows operations staff to quickly detect problems and identify that a problem is still ongoing, avoiding the case of investigating an issue a-priori when it may already have been resolved. In this paper we present details of the system architecture and provide a recipe for deployment suitable for both site and experiment teams.

scholarly journals A priori validation of CFD modelling of hydrocarbon pool fires

2018 ◽  
Vol 56 ◽  
pp. 18-31 ◽  
Author(s):  
Borja Rengel ◽  
Christian Mata ◽  
Elsa Pastor ◽  
Joaquim Casal ◽  
Eulàlia Planas
Keyword(s):  
A Priori ◽  
Pool Fires ◽  
Cfd Modelling ◽  
Hydrocarbon Pool ◽  
Hydrocarbon Pool Fires

scholarly journals NaV1.5 knockout in iPSCs: a novel approach to study NaV1.5 variants in a human cardiomyocyte environment

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marion Pierre ◽  
Mohammed Djemai ◽  
Hugo Poulin ◽  
Mohamed Chahine
Keyword(s):  
Contractile Activity ◽  
Somatic Tissue ◽  
Patient Specific ◽  
Ipsc Line ◽  
Healthy Human ◽  
Novel Approach ◽  
Electrophysiological Recordings ◽  
Cardiac Sodium Channel ◽  
Induced Pluripotent ◽  
Genomic Editing

AbstractCardiomyocytes derived from patient-specific induced pluripotent stem cells (iPSC-CMs) successfully reproduce the mechanisms of several channelopathies. However, this approach involve cell reprogramming from somatic tissue biopsies or genomic editing in healthy iPSCs for every mutation found and to be investigated. We aim to knockout (KO) NaV1.5, the cardiac sodium channel, in a healthy human iPSC line, characterize the model and then, use it to express variants of NaV1.5. We develop a homozygous NaV1.5 KO iPSC line able to differentiate into cardiomyocytes with CRISPR/Cas9 tool. The NaV1.5 KO iPSC-CMs exhibited an organized contractile apparatus, spontaneous contractile activity, and electrophysiological recordings confirmed the major reduction in total Na+ currents. The action potentials (APs) exhibited a reduction in their amplitude and in their maximal rate of rise. Voltage optical mapping recordings revealed that the conduction velocity Ca2+ transient waves propagation velocities were slow. A wild-type (WT) NaV1.5 channel expressed by transient transfection in the KO iPSC-CMs restored Na+ channel expression and AP properties. The expression of NaV1.5/delQKP, a long QT type 3 (LQT3) variant, in the NaV1.5 KO iPSC-CMs showed that dysfunctional Na+ channels exhibited a persistent Na+ current and caused prolonged AP duration that led to arrhythmic events, characteristics of LQT3.

High incidence of ICA anterior wall aneurysms in patients with an anomalous origin of the ophthalmic artery: possible relevance to the pathogenesis of aneurysm formation

2014 ◽  
Vol 120 (1) ◽  
pp. 93-98 ◽  
Author(s):  
Masahiro Indo ◽  
Soichi Oya ◽  
Michihiro Tanaka ◽  
Toru Matsui
Keyword(s):  
Carotid Artery ◽  
Internal Carotid Artery ◽  
Ophthalmic Artery ◽  
Internal Carotid ◽  
Medical Center ◽  
Anterior Wall ◽  
Dissecting Aneurysm ◽  
Anomalous Origin ◽  
Aneurysm Formation ◽  
Saccular Aneurysms

Object Surgery for aneurysms at the anterior wall of the internal carotid artery (ICA), which are also referred to as ICA anterior wall aneurysms, is often challenging. A treatment strategy needs to be determined according to the pathology of the aneurysm—namely, whether the aneurysm is a saccular aneurysm with firm neck walls that would tolerate clipping or coiling, a dissecting aneurysm, or a blood blister–like aneurysm. However, it is not always possible to properly evaluate the condition of the aneurysm before surgery solely based on angiographic findings. Methods The authors focused on the location of the ophthalmic artery (OA) in determining the pathology of ICA anterior wall aneurysms. Between January 2006 and December 2012, diagnostic cerebral angiography, for any reason, was performed on 1643 ICAs in 855 patients at Saitama Medical Center. The authors also investigated the relationship between the origin of the OA and the incidence of ICA anterior wall aneurysms. The pathogenesis was also evaluated for each aneurysm based on findings from both angiography and open surgery to identify any correlation between the location where the OA originated and the conditions of the aneurysm walls. Results Among 1643 ICAs, 31 arteries (1.89%) were accompanied by an anomalous origin of the OA, including 26 OAs originating from the C3 portion, 3 originating from the C4 portion, and 2 originating from the anterior cerebral artery. The incidence of an anomalous origin of the OA had no relationship to age, sex, or side. Internal carotid artery anterior wall aneurysms were observed in 16 (0.97%) of 1643 ICAs. Female patients had a significantly higher risk of having ICA anterior wall aneurysms (p = 0.026). The risk of ICA anterior wall aneurysm formation was approximately 50 times higher in patients with an anomalous origin of the OA (25.8% [8 of 31]) than in those with a normal OA (0.5% [8 of 1612], p < 0.0001). Based on angiographic classifications, saccular aneurysms were significantly more common in patients with an anomalous origin of the OA than in those with a normal OA (p = 0.041). Ten of 16 patients with ICA anterior wall aneurysms underwent craniotomies. Based on the intraoperative findings, all 6 aneurysms with normal OAs were dissecting or blood blister–like aneurysms, not saccular aneurysms. Conclusions There was a close relationship between the location of the OA origin and the predisposition to ICA anterior wall aneurysms. Developmental failure of the OA and subsequent weakness of the vessel wall might account for this phenomenon, as previously reported regarding other aneurysms related to the anomalous development of parent arteries. The data also appear to indicate that ICA anterior wall aneurysms in patients with an anomalous origin of the OA tend to be saccular aneurysms with normal neck walls. These findings provide critical information in determining therapeutic strategies for ICA anterior wall aneurysms.

Flow-Induced Wall Mechanics of Patient-Specific Aneurysmal Cerebral Arteries: Nonlinear Isotropic vs. Anisotropic Wall Stress

2008 ◽  
Author(s):  
S. L. Cornejo ◽  
J. F. Rodriguez ◽  
A. A. Valencia ◽  
A. M. Guzman ◽  
E. A. Finol
Keyword(s):  
Intracranial Aneurysms ◽  
Cerebral Arteries ◽  
Constitutive Models ◽  
Spherical Geometry ◽  
Decisive Role ◽  
Wall Stress ◽  
Patient Specific ◽  
Initial Shape ◽  
Pulsatile Pressure ◽  
Saccular Aneurysms

There are several biomechanical factors involved in the formation, growth, remodeling, and eventual rupture of intracranial aneurysms. In particular, hemodynamic forces have a decisive role in the biomechanical environment of the aneurysmal cerebral vasculature. Most of the previous studies on vascular mechanics assessment of intracranial aneurysms are based on idealized geometries, where it has been suggested [1] that it is highly unlikely that saccular aneurysms expand due to a limit point instability. In addition, it has been reported [2] that some saccular aneurysms with non-spherical initial shape tend to become spherical when subjected to uniform pressure, because a spherical geometry is optimal to resist the pressure load, yielding a homogenous wall stress. In the present work, we present a comparison between anisotropic and isotropic constitutive models, which allows us to analyze the biomechanics of patient-specific cerebral aneurysmal arteries subjected to flow-induced pulsatile pressure. The results describe the effects of material anisotropy in the resulting wall mechanics of the intracranial vasculature geometries.

Using Deconvolution to Improve PET Spatial Resolution in OSEM Iterative Reconstruction

2007 ◽  
Vol 46 (02) ◽  
pp. 231-235 ◽  
Author(s):  
I. Castiglioni ◽  
G. Russo ◽  
M. Tana ◽  
F. Dell'Acqua ◽  
M. Gilardi ◽  
...  
Keyword(s):  
Image Reconstruction ◽  
Spatial Resolution ◽  
Penalty Function ◽  
Iterative Reconstruction ◽  
A Priori ◽  
Image Deconvolution ◽  
A Priori Information ◽  
Novel Approach ◽  
Priori Information ◽  
Pet Image Reconstruction

Summary Objectives : A novel approach to the PET image reconstruction is presented, based on the inclusion of image deconvolution during conventional OSEM reconstruction. Deconvolution is here used to provide a recovered PET image to be included as “a priori" information to guide OSEM toward an improved solution. Methods : Deconvolution was implemented using the Lucy-Richardson (LR) algorithm: Two different deconvolution schemes were tested, modifying the conventional OSEM iterative formulation: 1) We built a regularizing penalty function on the recovered PET image obtained by deconvolution and included i in the OSEM iteration. 2) After each conventional global OSEM iteration, we deconvolved the resulting PET image and used this “recovered" version as the initialization image for the next OSEM iteration. Tests were performed on both simulated and acquired data. Results : Compared to the conventional OSEM, both these strategies, applied to simulated and acquired data, showed an improvement in image spatial resolution with better behavior in the second case. In this way, small lesions, present on data, could be better discriminated in terms of contrast. Conclusions : Application of this approach to both simulated and acquired data suggests its efficacy in obtaining PET images of enhanced quality.

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