Development of an Abdominal Aortic Aneurysm Ruptures Mechanism Using a Geometric Analytical Technique

2014 ◽  
Author(s):  
A. H. Embong ◽  
A. M. Al-Jumaily ◽  
G. Mahadevan ◽  
A. Lowe ◽  
S. Sugita
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Analytical Technique ◽  
Abdominal Aortic ◽  
Risk Of Rupture ◽  
Wall Deformation ◽  
Rupture Mechanism

Current ultrasound approaches practice probe for diagnosing instantaneous abdominal aortic aneurysms (AAA) based on arterial tissue deformation. However, tracking the progression of potential aneurysms, and predicting the risk of rupture is based on the diameter of the aneurysm and is still an insufficient method: Larger diameter aneurysms do not always lead to ruptures, and smaller diameter aneurysms unexpectedly rupture. In order to improve diagnostic accuracy of ultrasound imaging techniques, this paper presents geometric analyses of patient-specific instant deformations as a means to develop an aneurysm rupture mechanism. Segmented AAA images were used to analyze dependent elements that contribute to a three-dimensional (3-D) aneurysm reconstructive model using proposed Patient-Specific Aneurysm Rupture Predictor (P-SARP) method. The outcomes indicate that the proposed technique has the ability to associate the distortion of wall deformation with geometric analyses. This method can positively be integrated with established ultrasound techniques for improvements in the accuracy of future diagnoses of potential AAA ruptures.

Flow-Induced Wall Pressure Under Average Resting Hemodynamic Conditions for Patient-Specific Abdominal Aortic Aneurysms

2002 ◽  
Author(s):  
Ender A. Finol ◽  
Shoreh Hajiloo ◽  
Keyvan Keyhani ◽  
David A. Vorp ◽  
Cristina H. Amon
Keyword(s):  
Imaging Techniques ◽  
Abdominal Aortic Aneurysms ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Mortality And Morbidity ◽  
Abdominal Aortic ◽  
Lethal Event ◽  
Overall Mortality

Abdominal Aortic Aneurysms (AAAs) are characterized by a continuous dilation of the infrarenal segment of the abdominal aorta. Despite significant improvements in surgical procedures and imaging techniques, the mortality and morbidity rates associated with untreated ruptured AAAs are still outrageously high. AAA disease is a health risk of significant importance since this kind of aneurysm is mostly asymptomatic until its rupture, which is frequently a lethal event with an overall mortality rate in the 80% to 90% range. From a purely biomechanical viewpoint, aneurysm rupture is a phenomenon that occurs when the mechanical stress acting on the dilating inner wall exceeds its failure strength. Since the internal mechanical forces are maintained by the dynamic action of blood flowing in the aorta, the quantification of the hemodynamics of AAAs is essential for the characterization of their biomechanical environment.

Anatomically Accurate Haemodynamic Simulations of Abdominal Aortic Aneurysms

2003 ◽  
Author(s):  
Evangelos Boutsianis ◽  
Thomas Frauenfelder ◽  
Simon Wildermuth ◽  
Dimos Poulikakos ◽  
Yiannis Ventikos
Keyword(s):  
Interventional Procedure ◽  
Imaging Techniques ◽  
Objective Assessment ◽  
Three Dimensional ◽  
Quantitative Information ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Significant Information ◽  
Comprehensive Collection ◽  
Abdominal Aortic

The pulsatile blood flow field in a patient-specific pathology of a large Abdominal Aortic Aneurysm (AAA) is being simulated, both pre and post interventionally. The anatomies of the aortic wall and blood lumen have been derived by digitized Computerized Tomography (CT) scans. Three dimensional unsteady computational fluid dynamics simulations have provided a comprehensive collection of quantitative information on the haemodynamics and the flow features that present themselves in both the temporal and spatial spaces. The focus lies on alterations in the haemodynamics triggered by the interventional procedure itself, which consists of the endoluminal introduction of a stent-graft. Significant information may also be deduced concerning the hydrodynamic loading of such implants. Computational tools of this nature, along with the non-invasive CT or Magnetic Resonance (MR) aortic imaging techniques, could enable an objective assessment of the possible effects of any interventional scenario in a virtual noninvasive environment both proximally and distally to the diseased region.

Method for Incorporating Three-Dimensional Residual Stresses Into Patient-Specific Simulations of Arteries

2013 ◽  
Author(s):  
David M. Pierce ◽  
Thomas E. Fastl ◽  
Hannah Weisbecker ◽  
Gerhard A. Holzapfel ◽  
Borja Rodriguez-Vila ◽  
...  
Keyword(s):  
Medical Imaging ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Abdominal Aortic ◽  
Model Geometry ◽  
Reconstructed Model

Through progress in medical imaging, image analysis and finite element (FE) meshing tools it is now possible to extract patient-specific geometries from medical images of, e.g., abdominal aortic aneurysms (AAAs), and thus to study clinically relevant problems via FE simulations. Medical imaging is most often performed in vivo, and hence the reconstructed model geometry in the problem of interest will represent the in vivo state, e.g., the AAA at physiological blood pressure. However, classical continuum mechanics and FE methods assume that constitutive models and the corresponding simulations start from an unloaded, stress-free reference condition.

scholarly journals On the Relative Impact of Intraluminal Thrombus Heterogeneity on Abdominal Aortic Aneurysm Mechanics

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Joseph R. Leach ◽  
Evan Kao ◽  
Chengcheng Zhu ◽  
David Saloner ◽  
Michael D. Hope
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Rupture Risk ◽  
Intraluminal Thrombus ◽  
Element Analysis ◽  
Aneurysm Wall ◽  
Abdominal Aortic

Intraluminal thrombus (ILT) is present in the majority of abdominal aortic aneurysms (AAA) of a size warranting consideration for surgical or endovascular intervention. The rupture risk of AAAs is thought to be related to the balance of vessel wall strength and the mechanical stress caused by systemic blood pressure. Previous finite element analyses of AAAs have shown that ILT can reduce and homogenize aneurysm wall stress. These works have largely considered ILT to be homogeneous in mechanical character or have idealized a stiffness distribution through the thrombus thickness. In this work, we use magnetic resonance imaging (MRI) to delineate the heterogeneous composition of ILT in 7 AAAs and perform patient–specific finite element analysis under multiple conditions of ILT layer stiffness disparity. We find that explicit incorporation of ILT heterogeneity in the finite element analysis is unlikely to substantially alter major stress analysis predictions regarding aneurysm rupture risk in comparison to models assuming a homogenous thrombus, provided that the maximal ILT stiffness is the same between models. Our results also show that under a homogeneous ILT assumption, the choice of ILT stiffness from values common in the literature can result in significantly larger variations in stress predictions compared to the effects of thrombus heterogeneity.

A Comparative Study of Biomechanical and Geometrical Attributes of Abdominal Aortic Aneurysms in the Asian and Caucasian Populations

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Tejas Canchi ◽  
Sourav S. Patnaik ◽  
Hong N. Nguyen ◽  
E. Y. K. Ng ◽  
Sriram Narayanan ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Gaussian Curvature ◽  
Wall Stress ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Backward Elimination ◽  
Abdominal Aortic ◽  
Highly Correlated ◽  
Peak Wall Stress

Abstract In this work, we provide a quantitative assessment of the biomechanical and geometric features that characterize abdominal aortic aneurysm (AAA) models generated from 19 Asian and 19 Caucasian diameter-matched AAA patients. 3D patient-specific finite element models were generated and used to compute peak wall stress (PWS), 99th percentile wall stress (99th WS), and spatially averaged wall stress (AWS) for each AAA. In addition, 51 global geometric indices were calculated, which quantify the wall thickness, shape, and curvature of each AAA. The indices were correlated with 99th WS (the only biomechanical metric that exhibited significant association with geometric indices) using Spearman's correlation and subsequently with multivariate linear regression using backward elimination. For the Asian AAA group, 99th WS was highly correlated (R2 = 0.77) with three geometric indices, namely tortuosity, intraluminal thrombus volume, and area-averaged Gaussian curvature. Similarly, 99th WS in the Caucasian AAA group was highly correlated (R2 = 0.87) with six geometric indices, namely maximum AAA diameter, distal neck diameter, diameter–height ratio, minimum wall thickness variance, mode of the wall thickness variance, and area-averaged Gaussian curvature. Significant differences were found between the two groups for ten geometric indices; however, no differences were found for any of their respective biomechanical attributes. Assuming maximum AAA diameter as the most predictive metric for wall stress was found to be imprecise: 24% and 28% accuracy for the Asian and Caucasian groups, respectively. This investigation reveals that geometric indices other than maximum AAA diameter can serve as predictors of wall stress, and potentially for assessment of aneurysm rupture risk, in the Asian and Caucasian AAA populations.

scholarly journals A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms

2014 ◽  
Vol 307 (12) ◽  
pp. H1786-H1795 ◽  
Author(s):  
Amirhossein Arzani ◽  
Ga-Young Suh ◽  
Ronald L. Dalman ◽  
Shawn C. Shadden
Keyword(s):  
Spin Echo ◽  
Aortic Aneurysms ◽  
Fast Spin Echo ◽  
Patient Specific ◽  
Black Blood ◽  
Hemodynamic Parameters ◽  
Dynamics Modeling ◽  
Spatially Resolved ◽  
Abdominal Aortic ◽  
Risk Of Rupture

Abdominal aortic aneurysm (AAA) is often accompanied by in traluminal thrombus (ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2- to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (>0.4) and low TAWSS (<1 dyn/cm2) did not appear to coincide with locations of thrombus deposition.

Estimation of wall properties and wall strength of aortic aneurysms using modern imaging techniques. One more step towards a patient-specific assessment of aneurysm rupture risk

2013 ◽  
Vol 81 (2) ◽  
pp. 212-215 ◽  
Author(s):  
Nikolaos Kontopodis ◽  
Efstratios Georgakarakos ◽  
Eleni Metaxa ◽  
Konstantinos Pagonidis ◽  
Yannis Papaharilaou ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Rupture Risk ◽  
Modern Imaging ◽  
Wall Properties ◽  
Wall Strength ◽  
Specific Assessment

scholarly journals Abdominal aortic aneurysm: Rupture of the anterior wall

2007 ◽  
Vol 60 (1-2) ◽  
pp. 80-84 ◽  
Author(s):  
Miroljub Draskovic ◽  
Sidor Misovic ◽  
Miodrag Jevtic ◽  
Momir Sarac
Keyword(s):  
Computed Tomography ◽  
Case Report ◽  
Imaging Techniques ◽  
Diagnostic Procedures ◽  
Anterior Wall ◽  
Aneurysm Rupture ◽  
Clinical Findings ◽  
Aortic Aneurysms ◽  
Diagnostic Tools ◽  
Abdominal Aortic

Introduction An aneurysm is a focal dilatation of an artery (aorta), involving an increase in diameter of at least 50% as compared to the expected normal diameter (over 3 cm). Abdominal aortic aneurysms (AAA) cause thousands of deaths every year, many of which can be prevented with timely diagnosis and treatment. AAA can be asymptomatic for many years, but in one third of patients whose aneurysm ruptured, the mortality rate is 90%. In the past, palpation of the abdomen was the preferred method for identifying AAA. However, diagnostic imaging techniques, such as ultrasonography and computed tomography are more accurate and offer opportunities for early detection of AAA. Case report This paper is a case report of an 83-year old female patient. She was admitted due to severe pain in the abdomen. We already knew about the AAA (from her medical history). After using all available diagnostic procedures, rupture or dissection of the AAA were not confirmed. The patient underwent emergency surgery. During the operation, rupture of the anterior wall of the aneurysm was found. The anterior wall was filled with parietal thrombus, which hermetically closed the perforation. The patient was successfully operated and recovered. Conclusion The aim of this case report was to point out that our diagnostic procedures failed to confirm the rupture of AAA. We decided to apply surgical treatment, based on medical experience, clinical findings, ultrasonography and computed tomography and during operation rupture of AAA was confirmed. Patients with an already diagnosed AAA, or patients with clinical picture of rupture or dissection, are in urgent need for surgery, no matter what diagnostic tools are being used.

Three-Dimensional Geometrical Characterization of Abdominal Aortic Aneurysms: Image-Based Wall Thickness Distribution

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Giampaolo Martufi ◽  
Elena S. Di Martino ◽  
Cristina H. Amon ◽  
Satish C. Muluk ◽  
Ender A. Finol
Keyword(s):  
Wall Thickness ◽  
Three Dimensional ◽  
Aortic Aneurysms ◽  
Maximum Diameter ◽  
Patient Specific ◽  
Future Research ◽  
Geometrical Shape ◽  
Rupture Risk ◽  
Abdominal Aortic ◽  
Elective Repair

The clinical assessment of abdominal aortic aneurysm (AAA) rupture risk is based on the quantification of AAA size by measuring its maximum diameter from computed tomography (CT) images and estimating the expansion rate of the aneurysm sac over time. Recent findings have shown that geometrical shape and size, as well as local wall thickness may be related to this risk; thus, reliable noninvasive image-based methods to evaluate AAA geometry have a potential to become valuable clinical tools. Utilizing existing CT data, the three-dimensional geometry of nine unruptured human AAAs was reconstructed and characterized quantitatively. We propose and evaluate a series of 1D size, 2D shape, 3D size, 3D shape, and second-order curvature-based indices to quantify AAA geometry, as well as the geometry of a size-matched idealized fusiform aneurysm and a patient-specific normal abdominal aorta used as controls. The wall thickness estimation algorithm, validated in our previous work, is tested against discrete point measurements taken from a cadaver tissue model, yielding an average relative difference in AAA wall thickness of 7.8%. It is unlikely that any one of the proposed geometrical indices alone would be a reliable index of rupture risk or a threshold for elective repair. Rather, the complete geometry and a positive correlation of a set of indices should be considered to assess the potential for rupture. With this quantitative parameter assessment, future research can be directed toward statistical analyses correlating the numerical values of these parameters with the risk of aneurysm rupture or intervention (surgical or endovascular). While this work does not provide direct insight into the possible clinical use of the geometric parameters, we believe it provides the foundation necessary for future efforts in that direction.

scholarly journals Does the Intraluminal Thrombus Provoke the Rupture of the Abdominal Aortic Aneurysm Wall?

2021 ◽  
Vol 11 (21) ◽  
pp. 9941
Author(s):  
Mohammed Almijalli
Keyword(s):  
Computer Modelling ◽  
Aortic Aneurysms ◽  
Oxygen Flow ◽  
Patient Specific ◽  
Aortic Blood Flow ◽  
Intraluminal Thrombus ◽  
Volume Percentage ◽  
Aneurysm Wall ◽  
Abdominal Aortic ◽  
Risk Of Rupture

The role of intraluminal thrombus (ILT) in the rupture of abdominal aortic aneurysms (AAA) is controversial, and it is unclear whether it increases or decreases the risk of rupture. This research aims to find a clear answer to this question. Previous computer modelling suggests that an ILT lowers oxygen dissemination to the AAA wall, contributing to wall thinning. The methodology used in this study determines the amount of oxygen reaching the aneurysm wall after passing through the ILT by using the porous nature of the ILT to recreate the condition as closely as feasible. Using computed tomographic images, patient-specific three-dimensional (3D) AAA geometries were recreated. Modelling blood and oxygen flow in AAA was obtained using a computational fluid dynamics (CFD) approach. Our findings indicated that the oxygen volume percentage had completely reached the aneurysm wall. Only at the inlet and outflow did the greatest wall shear stress (WSS) occur, with a significant drop in the central region of the aneurysm wall. CFD was used to calculate the velocity, pressure, and WSS of aortic blood flow. ILT had no effect on oxygen flow to the aneurysm wall, disproving the theory that it produces local hypoxia.

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